WET-SPUN LAMIN-BASED FIBERS

FIELD OF THE INVENTION

The present invention relates generally to the field of lamin-based fibers.

BACKGROUND OF THE INVENTION

Proteinaceous fibers are ubiquitous in biological systems and occur in a wide range of structures exhibiting a broad spectrum of mechanical properties, from hard to elastic, to accommodate diverse functional requirements. Fibrous proteins have unique physical properties, which are exploited in the design of novel biomaterials, such as scaffolds and fibers. Generally, these protein fibers possess high biocompatibility, and are ideal for tissue engineering, wound dressing, and drug delivery applications. Fibers based on natural and regenerated silk from the silkworm Bombyx mori and dragline silk proteins of spiders, have been rigorously studied due to their toughness and stiffness, which are greater than those of most natural protein-based fibers and synthetic materials. High stiffness and toughness values are also observed in the native micrometer-sized threads (diameter of 1-2 μm) of the hagfish slime, which are composed of “keratin-like” proteins (α and γ). Although hagfish threads have been spun successfully from recombinantly expressed proteins, the mechanical properties of these fibers were inferior to those of the native fibers. These findings suggested that unique organization of the proteins, as in the native fibers, need to be faithfully mimicked to achieve high toughness and stiffness.

SUMMARY OF THE INVENTION

In one aspect of the invention, there is provided a fiber comprising a lamin-based protein, wherein the fiber is characterized by a diameter between 10 μm and 180 μm.

In some embodiments, the lamin-based protein comprises an A-type lamin, a B-type lamin or both.

In some embodiments, the B-type lamin comprises an amino acid sequence as set forth in SEQ ID NO: 1, wherein X₁comprises Gln or Lys, including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the fiber further comprises any of: (i) an N-terminal region comprising the amino acid sequence as set forth in SEQ ID NO: 2, including any functional analog having at least 70% sequence homology thereto; and (ii) a C-terminal region comprising the amino acid sequence as set forth in SEQ ID NO: 3, including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the A-type lamin comprises an amino acid sequence as set forth in SEQ ID NO: 4, wherein X₂is Glu or Lys, including any functional analog having at least 70% sequence homology thereto.

In another aspect of the invention, there is provided a fiber comprising an A-type lamin-based protein, wherein the fiber is characterized by a diameter between 10 μm and 180 μm.

In some embodiments, the repetitive region comprises an amino acid sequence as set forth in SEQ ID NO: 4, wherein X₂is Glu or Lys, including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the amino acid sequence further comprises any of: (i) an N-terminal region comprising the amino acid sequence as set forth in SEQ ID NO: 5; and (ii) a C-terminal region comprising the amino acid sequence as set forth in SEQ ID NO: 6. In some embodiments, the fiber further comprises a B-type lamin.

In some embodiments, the fiber is characterized by at least one mechanical property selected from: —Yield strength between 1 MPa and 1000 MPa; —tensile strength between 1 MPa and 1000 MPa; —fracture strain between 10% and 500%; —toughness between 30 MJ/m³and 1000 MJ/m³and—a Young's Modulus between 0.001 GPa and 30 GPa.

In some embodiments, the protein is characterized by a α-helix to β-sheet transition between 3% and 50%, upon stretching thereof.

In some embodiments, the fiber is characterized by a diameter between 20 μm and 80 μm.

In another aspect of the invention, there is provided a fiber comprising a B-type lamin-based protein, the fiber is characterized by a (i) diameter between 10 μm and 180 μm; and (ii) the B-type lamin-based protein comprises an amino acid as set forth in SEQ ID NO: 1, including any functional analog having at least 70% sequence homology thereto; wherein: if X₁is Gln, than the fiber is characterized by any of: (i) a residual amount of an alcohol; (ii) toughness of greater than 190 MJ/m³and (ii) the protein is characterized by a α-helix to β-sheet transition between 3% and 50%, upon stretching thereof.

In some embodiments, the fiber is characterized by a diameter between 30 and 60 μm.

In some embodiments, the lamin-based protein further comprises any of: i. an N-terminal region comprising the amino acid sequence SEQ ID NO: 2 or any functional analog having at least 70% sequence homology thereto; ii. a C-terminal region comprising the amino acid sequence SEQ ID NO: 3 or any functional analog having at least 70% sequence homology thereto.

In some embodiments, the fiber is characterized by at least one mechanical property selected from: —Yield strength 1 MPa and 1000 MPa; —tensile strength between 1 MPa and 1000 MPa; —fracture strain between 10% and 500%; —toughness between 30 MJ/m³and 1000 MJ/m³; and—a Young's Modulus between 0.001 GPa and 30 GPa.

In some embodiments, each repeat independently has a molecular weight in the range of 20 kDa to 80 kDa.

In some embodiments, the fiber is a stretched fiber.

In some embodiments, the fiber comprises a plurality of lamin-based protein arranged in a form of paracrystals; wherein each of the paracrystals is characterized by a dimension selected from: (i) a width between 1 nm and 500 nm; (ii) a length between 0.5 mm and 1 cm, or both (i) and (ii).

In some embodiments, the lamin-based protein is an isolated protein.

In some embodiments, the fiber is obtained by expression in a bacterium.

In some embodiments, the protein is characterized by secondary structure comprising a α-helix: β-sheet ratio between 5:1 and 1:1.

In some embodiments, the fiber further comprises a hydrophobic coating.

In some embodiments, the hydrophobic coating comprises a vegetable oil, a mineral oil, fatty acids, isobutyl-stearate, tallow fatty acid 2-ethylhexyl ester, polyol carboxylic acid ester, coconut oil fatty acid ester of glycerol, alkoxylated glycerol, a silicone, dimethyl polysiloxane, a polyalkylene glycol, polyethylene oxide, a propylene oxide copolymer, or any combination thereof.

In another aspect of the invention, there is provided an article comprising the fiber of the present invention.

In some embodiments, the article is in a form of a woven or a non-woven substrate.

In some embodiments, the article is characterized by at least one improved mechanical property as compared to the property for the article free of the fiber, wherein the property is selected from the group consisting of: Young's modulus, tensile strength, fracture strain, yield point, toughness, work to failure, impact strength, tear strength, flexural modulus, flexural strain and stress at a specific percentage elongation.

In another aspect of the invention, there is provided a method for obtaining the fiber of the present invention, comprising the steps of: a. providing a lamin-based protein at a concentration between 10 mg/mL and 400 mg/mL; and b. injecting the lamin-based protein into a coagulation solution, thereby forming the fiber.

In some embodiments, the coagulation solution is characterized by a viscosity between 0.45 cP and 3 cP, or more than 0.7 cP.

In some embodiments, the injecting is at a flow rate of at least 0.1 ml/h.

In some embodiments, the coagulation solution comprises (i) an alcohol (ii) an aqueous solution (ii) a buffer solution, or any combination thereof.

In some embodiments, the alcohol is selected from methanol (MeOH), ethanol (EtOH), propanol (PrOH), isopropyl alcohol (IPA), or any combination thereof.

In some embodiments, the coagulation solution comprises between 50% (v/v) and 100% (v/v) of the alcohol.

In some embodiments, the coagulation solution comprises a cross-linker.

In some embodiments, the coagulation solution comprises between 1 mM and 100 mM of CaCl₂).

In some embodiments, the method further comprises at least one step of (i) drying the fiber, and (ii) stretching the fiber.

In some embodiments, the method further comprises a step (c) contacting the fiber with a hydrophobic agent, thereby forming a coating layer on the fiber.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1H present Ce-lamin-based fiber structures (FIG. 1A): the full-length-Ce-lamin gene is divided into three structural domains: head, rod, and tail. The rod domain comprises three α-helical coiled-coil segments (1A, 1B, and 2) that are connected by L1 and L12 linkers. A major part of the tail domain (105 aa) folds into an immunoglobulin (Ig)-like globular structure. Deletion of the entire tail domain or both head and tail domains led to the rod-Ce-lamin and rod-tail-Ce-lamin constructs; a schematic representation of the recombinant Ce-lamins, produced in E. coli (FIG. 1B) as inclusion bodies, were solubilized in urea buffer. The fibers were produced via wet spinning of a water-based Ce-lamin solution into Ca⁺²-ions containing aqueous solution; and SEM images of rod (FIG. 1C), rod-tail (FIG. 1D), full-length (FIG. 1E) Ce-lamin fibers before the tensile test, illustrating their fibrous morphology, and higher magnification of the SEM images of rod (FIG. 1F), rod-tail (FIG. 1G), and full-length (FIG. 1H) Ce-lamin fibers formed at the optimal assembly conditions. Insets are the lower magnification views;

FIGS. 2A-2C present the internal structures of Ce-lamin based fibers: TEM images of 70 nm-thick cross-section of rod-, rod-tail-, and full-length Ce-lamin-based wet fibers spun at the optimal assembly conditions (FIG. 2A). Series of images under gradually increasing magnification of the insets illustrates that Ce-lamin fibers internal structure is an intricate network of paracrystals. Cross-section analysis of rod, rod-tail, and full-length Ce-lamin-based wet fibers imaged using TEM (FIG. 2B): Diversity in structure of fibers were detected as injection velocity with increasing injection velocities, 0.5, 1, and 3.5 mL/h, into buffers containing 20 mM or 50 mM CaCl₂. Most of the fibers contained random networks of paracrystals exhibiting a wide range of diameters (Table 4). Electron micrograph of paracrystals assembled from full-length Ce-lamin (FIG. 2C). The average repeat-length (dark/black and bright/white segment) were measured as depicted, i.e., the length between the two centers of the black regions;

FIG. 3 is a graph of stress-strain curves of the rod-, rod-tail, and full-length-Ce-lamin fibers at the optimal assembly conditions; under these conditions, the three constructs demonstrated optimal mechanical properties;

FIGS. 4A-4D are bar graphs of the effects of CaCl₂) concentration in the coagulation bath, injection flow rate, and crosshead velocity on the diameter, stiffness, and toughness of rod-(FIG. 4A), rod-tail-(FIG. 4B), and full-length (FIG. 4C) Ce-lamin-based fibers. Crosshead velocities are 0.3 mm/min (left bar), 10 mm/min (middle bar), and 100 mm/min (right bar); and SEM image of full-length Ce-lamin fibers formed at injection rate 1 mL/h in coagulation bath containing 50 mM CaCl₂) (FIG. 4D). The image was taken after the tensile test;

FIGS. 5A-5C present secondary structure analysis by Raman spectroscopy: experimental Raman spectra of the rod-(FIG. 5A), rod-tail-(FIG. 5B), and full-length (FIG. 5C) Ce-lamin-based fibers described in FIG. 3, show a peak shift before and after the mechanical test. The peaks are found at the amide I band region and correspond to α-helix (1650 cm⁻¹) and β-sheet/random coil (1667 cm⁻¹) structures. Graphical illustration (middle panel) of the evaluation of the relative increase of β-sheet/random coil structures performed by EM algorithm statistical approach;

FIGS. 6A-6B present a structural model of Ce-lamin-based fiber assembly: the basic building block of Ce-lamins is the coiled-coil dimer. Dimers polymerize in head-to-tail fashion to form polymers of dimers that are then laterally associated to form tetrameric protofilaments. The protofilaments are most probably the basic building blocks of all higher order lamin structures, in vitro and in the cell nucleus. The next step is the association of protofilaments into paracrystals whose interconnection into a random network constitutes the internal structure of Ce-lamin fibers (FIG. 6A). In response to stretching, the paracrystals/protofilaments are reorganized and aligned along the long axis of the fiber (FIG. 6B);

FIGS. 7A-B are graphs representing α-β transition propagation during tensile test stop at different strains and depicted on typical stress-strain curves of the full-length-Ce-lamin fibers assembled in 70% ethanol (7A), and Ce-lamin fibers assembled in an aqueous buffer containing 20 mM CaCl₂) (7B);

FIG. 8 is a Raman spectroscopy curve analysis of the full-length-Ce-lamin fibers assembled in 70% ethanol;

FIGS. 9A-9D are SEM images showing dry Ce-lamin fibers assembled in alcoholic solutions before tensile test: fiber formed in 70% ethanol (FIG. 9A), fiber formed in 50% ethanol (FIG. 9B), fiber formed in 70% IPA (FIG. 9C) and fiber formed in 50% IPA (FIG. 9D);

FIGS. 10A-10C are SEM images showing dry Ce-lamin fibers assembled in alcoholic solutions after tensile test: fiber formed in 70% ethanol and stretched to 30% strain (FIG. 10A), fiber formed in 70% IPA and stretched to 30% strain (FIG. 10B) and fiber formed in 70% ethanol and stretched until failure (FIG. 10C); and

FIG. 11 is a graph of stress-strain curves of the Q159K-Ce-lamin fibers assembled in alcoholic solutions in water (Et-Ethanol, IPA-Isopropanol).

FIGS. 12A-D are graphs and RAMAN spectra showing the mechanical and structural behavior in the elastic region of Ce-lamin fibers assembled in an aqueous buffer containing 20 mM CaCl₂(12A, 12C) or 70% ethanol (12B, 12D) upon five cycles strain test. FIGS. 12A-B show graphs of the mechanical behavior of the Ce-lamin fibers assembled in an aqueous buffer containing 20 mM CaCl₂(12A), and 70% ethanol (12B).

FIGS. 12C-D show RAMAN spectra of the Ce-lamin fibers assembled in an aqueous buffer containing 20 mM CaCl₂(12C), and 70% ethanol (12D).

DETAILED DESCRIPTION OF THE INVENTION

According to some embodiments, the present invention provides a fiber comprising a lamin-based protein, wherein the fiber is characterized by an average diameter between 1 μm and 1000 μm, and is further characterized by an average length of at least 0.1 cm. In some embodiments, the fiber is a lamin-based fiber, wherein the fiber is obtained via a wet spinning process. The inventors observed that wet-spun fibers formed by injecting a lamin-based protein into a coagulation bath are characterized by a sufficient length, so as to result in fibers with superior mechanical properties, compared to analogous self-assembled fibers. The present invention is based, in part, on the surprising finding that such wet-spun fibers are characterized by a toughness and stiffness comparable to natural dragline spider silk fibers and natural hagfish slime threads.

Furthermore, the present invention is based, in part, on the surprising finding that fibers injected into alcoholic coagulation solutions were characterized by superior mechanical strength and by improved elasticity when compared to fibers injected into aqueous coagulation solutions. Such fibers were further characterized by a specific RAMAN pattern, as disclosed hereinbelow. The inventors postulated that the superior mechanical properties of the fibers obtained from alcoholic coagulation are related to the α-helix to β-sheet transition pattern upon stretching the fiber, as characterized by RAMAN spectroscopy (see e.g. FIG. 7A). The α-helix to β-sheet transition (e.g. of at least 20%) occurs in the fibers obtained from alcoholic coagulation already in the elastic region (e.g. about 6% strain), whereas fibers obtained from aqueous coagulation solutions demonstrated α-helix to β-sheet transition only upon full stretching (about 100% strain, or more see FIG. 7B).

Moreover, the present invention is based, in part, on the surprising finding that coated fibers of the invention (e.g. comprising a hydrophobic coating) exhibited a significant improvement of the mechanical strength, compared to similar uncoated fibers.

According to some embodiments, the present invention provides a method for obtaining a fiber comprising a lamin-based protein, wherein the fiber is characterized by a diameter between 10 μm and 180 μm, comprising the steps of: providing a lamin-based protein at a concentration between 10 mg/mL and 400 mg/mL; and injecting the lamin-based protein into a coagulation solution, thereby forming the fiber.

The present invention is based, in part, on the finding that the concentration of the lamin-based protein is crucial for the formation of the fibers with the desired structure, thickness, and mechanical properties.

Lamin-Based Fibers

According to an aspect of some embodiments of the present invention there is provided a fiber comprising a lamin-based protein. In some embodiments, the fiber is a lamin-based protein fiber. In some embodiments, the fiber is characterized by a diameter between 1 μm and 1000 μm, between 1 μm and 200 μm, between 1 μm and 500 μm, between 1 μm and 300 μm, between 1 μm and 400 μm, between 1 μm and 700 μm, between 50 μm and 1000 μm, between 50 μm and 500 μm, between 50 μm and 300 μm, between 50 μm and 200 μm, between 2 μm and 200 μm, between 3 μm and 200 μm, between 5 μm and 200 μm, between 7 μm and 200 μm, between 9 μm and 200 μm, between 1 μm and 190 μm, between 2 μm and 190 μm, between 3 μm and 190 μm, between 5 μm and 190 μm, between 7 μm and 190 μm, between 9 μm and 190 μm, between 10 μm and 180 μm, between 15 μm and 180 μm, between 20 μm and 180 μm, between 25 μm and 180 μm, between 30 μm and 180 μm, between 50 μm and 180 μm, between 65 μm and 180 μm, between 10 μm and 100 μm, between 15 μm and 100 μm, between 20 μm and 100 μm, between 25 μm and 100 μm, between 30 μm and 100 μm, between 50 μm and 100 μm, between 65 μm and 100 μm, between 10 μm and 80 μm, between 15 μm and 80 μm, between 20 μm and 80 μm, between 25 μm and 80 μm, between 30 μm and 80 μm, between 50 μm and 80 μm, between 65 μm and 80 μm, between 10 μm and 50 μm, between 15 μm and 50 μm, between 20 μm and 50 μm, between 25 μm and 50 μm, or between 30 μm and 50 μm, including any range therebetween. Each possibility represents a separate embodiment of the invention. The term “diameter”, as used herein refers to the average cross-section of the dry fibers. The cross-section of the fiber can be determined by TEM, SEM or by optical microscopy.

In some embodiments, the fiber is characterized by a uniform diameter distribution. In some embodiments, the fiber is characterized by a diameter distribution (SD) between 0.1 and 1.5, between 0.2 and 1.5, between 0.3 and 1.5, between 0.5 and 1.5, between 0.1 and 1.0, between 0.2 and 1.0, between 0.3 and 1.0, between 0.5 and 1.0, including any range therebetween. Each possibility represents a separate embodiment of the invention. In some embodiments, the diameter distribution is quantified by the standard deviation (SD).

In some embodiments, the fiber is characterized by a length of at least 0.01 cm, at least 0.1 cm, at least 1 cm, at least 2 cm, at least 5 cm, at least 10 cm, at least 50 cm, at least 100 cm, at least 500 cm, at least 1000 cm, or at least 10.000 cm, between 0.01 and 10.000 cm, between 0.01 and 100.000 cm, between 0.05 and 10.000 cm, including any value therebetween. Each possibility represents a separate embodiment of the invention. The term “length”, as used herein refers to the average length of the dry fibers.

In some embodiments, the lamin-based protein comprises an A-type lamin, a B-type lamin or both.

As used herein, “lamin” refers to fibrous proteins in type V intermediate filaments (IF), that provide structural function and transcriptional regulation in the cell nucleus. Like all IF proteins, lamins have a tripartite structure consisting of a long α-helical domain flanked by globular amino-terminal (head), carboxy-terminal (tail) domains and central α-helical or rod domain. Lamins are classified as A-type and B-type. The B-type lamins are expressed in most cell types, whereas A-type lamins, which include lamin C, are generally expressed in differentiated tissues.

The terms “fiber” and “filament” are used interchangeably to refer to a fine cord of fibrous material. By “filament” is meant a slender, elongated, threadlike object or structure of indefinite length, ranging from microscopic length to lengths of a mile or greater. In some embodiments, the term “fiber” refers to the basic structure of the fibrous material, which cannot be further divided into smaller parts by using conventional industrial means (excluding harsh chemical conditions resulting in a denaturation and/or disassembly of the paracrystals or protofilaments composing the fiber). In contrast to a yarn (which is composed of two or more twisted or interlocked filaments) the fiber encompasses a basic structure which is not formed by a plurality of interlocked filaments. The fiber of the invention encompasses a continuous lamin-based fiber comprising a plurality of lamin-based proteins assembled in a form of paracrystals. The paracrystals within the fiber of the invention are substantially vertically aligned, along a longitudinal axis of the fiber. In some embodiments, according to the present invention the filament is a biofilament. By “biofilament” is meant a filament created from a protein. In some embodiments, the fiber or filament of the invention is in a crystalline state. In some embodiments, the fiber or filament of the invention is in a paracrystalline state or is a paracrystalline fiber. In some embodiments, the plurality of fibers of the invention form a paracrystalline material. In some embodiments, the fiber or filament of the invention consists essentially of repeating units of paracrystals.

In some embodiments, the average distance (also termed herein as “repeat length) between two adjacent paracrystals is between 20 and 60 nm, between about 30 and about 50 nm, between about 35 and about 50 nm, between about 30 and about 40 nm, between about 38 and about 45 nm, including any range or value therebetween. In some embodiments, the average distance between two adjacent paracrystals is about 40 nm. The average distance can be determined based on the TEM images of the fibers by measuring the length between the two centers of the adjacent dark regions (such as demonstrated in FIG. 2C).

In some embodiments, the fiber or filament of the invention is obtained via a wet spinning process (e.g. upon coagulation, as described herein). In some embodiments, the fibers or filaments of the invention are or consist essentially of wet-spun fibers. In some embodiments, the fiber or filament of the invention is devoid of self-assembled lamin fibers. The term “self-assembled fibers” as used herein encompasses fiber formed by self assembly of lamin protein into a protein network (e.g. by introducing the isolated proteins into CaCl₂solution) composed of micro-fibers, which are further wet spun into a yarn. In some embodiments, the self-assembled lamin fibers are in a form of a yarn composed of micro-fibers, characterized by an average length of below 1 μm, or below 1.5 μm, or between 300 and 1500 nm.

In some embodiments, there is provided a plurality of fibers or filaments of the invention characterized by an average length of at least 1 cm, at least 10 cm, at least 100 cm, at least 1000 cm, at least 100.000 cm or more including any range or value therebetween. In some embodiments, the plurality of fibers or filaments of the invention is characterized by an average length of between 0.1 cm and 10 cm, between 0.1 cm and 100 cm, between 0.1 cm and 1000 cm, between 0.1 cm and 10.000 cm, between 0.1 cm and 1 cm, between 0.1 cm and 5 cm, between 0.1 cm and 50 cm, between 1 cm and 10 cm, between 1 cm and 100 cm, between 1 cm and 1000 cm, between 1 cm and 10.000 cm, between 10 cm and 100 cm, between 10 cm and 1000 cm, between 10 cm and 10.000 cm, including any range or value therebetween. In some embodiments, the fiber or filament of the invention is substantially devoid of microfibers.

In some embodiments, the lamin-based protein fiber of the invention consists essentially of the lamin-based protein.

As used herein, the terms “polypeptide”, “peptide” and “protein” are used interchangeably to refer to two or more amino acids linked together. The terms “polypeptide”, “peptide”, “protein”, and “amino acid sequence” as used herein refer to any compound comprising naturally occurring or synthetic amino acid polymers or amino acid-like molecules including but not limited to compounds comprising amino and/or imino molecules. No particular size is implied by use of the term “peptide”, “oligopeptide”, “polypeptide”, or “protein”. Included within the definition are, for example, polypeptides containing one or more analogs of an amino acid (including, for example, unnatural amino acids, etc.), polypeptides with substituted linkages, as well as other modifications known in the art, both naturally occurring and non-naturally occurring (e.g., synthetic). Thus, synthetic oligopeptides, dimers, multimers (e.g., tandem repeats, multiple antigenic peptide (MAP) forms, linearly-linked peptides), cyclized, branched molecules and the like, are included within the definition. In another embodiment, the peptides, polypeptides and proteins described have modifications rendering them more stable while in the organism or more capable of penetrating into cells. In one embodiment, the terms “peptide”, “polypeptide” and “protein” apply to naturally occurring amino acid polymers. In another embodiment, the terms “peptide”, “polypeptide” and “protein” apply to amino acid polymers in which one or more amino acid residue is an artificial chemical analogue of a corresponding naturally occurring amino acid.

In some embodiments, the lamin-based protein comprises a B-type lamin. In some embodiments, the B-type lamin comprises n repeats of a repetitive region comprising an amino acid sequence: LQEKDHLTSLNSRLATYIDKVRQLEQENNRLQVQIRDIEVVEKKEKSNLADRFEA EKARLRRALDSAQDELAKYRIEYDAAKVEVKKLKPQVEKLERELAGAEEQALH AQSIADQS(X₁)AKQKTLQARNDKLVVENDDLKKQNITLRDTVEGLKKAVEDETL LRTAANNKIKALEEDLAFALQQHKGELEEVRHKRQVDMTTYAKQINDEYQSKL QDQIEEMRAQFKNNLHQNKTAFEDAYKNKLNAARERQEEAVSEAIHLRARVRD LETSSSGNASLIERLRSELDTLKRSFQEKLDDKDARIAELNQEIERMMSEFHDLLD VKIQLDAELKTYQALLE (SEQ ID NO: 1), including any functional analog having at least 70% sequence homology thereto. In some embodiments, X₁comprises Gln or Lys.

In some embodiments, the B-type lamin comprises n repeats of a repetitive region comprising an amino acid sequence: LQEKDHLTSLNSRLATYIDKVRQLEQENNRLQVQIRDIEVVEKKEKSNLADRFEA EKARLRRALDSAQDELAKYRIEYDAAKVEVKKLKPQVEKLERELAGAEEQALH AQSIADQS(X₁)AKQKTLQARNDKLVVENDDLKKQNITLRDTVEGLKKAVEDETL LRTAANNKIKALEEDLAFALQQHKGELEEVRHKRQVDMTTYAKQINDEYQSKL QDQIEEMRAQFKNNLHQNKTAFEDAYKNKLNAARERQEEAVSEAIHLRARVRD LETSSSGNASLIERLRSELDTLKRSFQEKLDDKDARIAELNQEIERMMSEFHDLLD VKIQLDAELKTYQALLEGEEERL (SEQ ID NO: 11), including any functional analog having at least 70% sequence homology thereto. In some embodiments, X₁comprises Gln or Lys.

In some embodiments, the B-type lamin comprises an amino acid sequence: LQEKDHLTSLNSRLATYIDKVRQLEQENNRLQVQIRDIEVVEKKEKSNLADRFEA EKARLRRADSAQDELAKYRIEYDAAKVEVKKLKPQVEKLERELAGAEEQALHA QSIADQSQAKQKTLQARNDKLVVENDDLKKQNITLRDTVEGLKKAVEDETLLRT AANNKIKALEEDLAFALQQHKGELEEVRHKRQVDMTTYAKQINDEYQSKLQDQI EEMRAQFKNNLHQNKTAFEDAYKNKLNAARERQEEAVSEAIHLRARVRDLETSS SGNASLIERLRSELDTLKRSFQEKLDDKDARIAELNQEIERMMSEFHDLLDVKIQL DAELKTYQALLEGEEERLNLTQEAPQNTSVHHVSFSSGGASAQRGVKRRRVVDV NGEDQDIDYLNRRSKLNKETVGPVGIDEVDEEGKWVRVANNSEEEQSIGGYKLV VKAGNKEASFQFSSRMKLAPHASATVWSADAGAVHHPPEVYVMKKQQWPIGD NPSARLEDSEGDTVSSITVEFSESSDPSDPADRCSIM (SEQ ID NO: 12), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 1, or to SEQ ID NO: 10, or to SEQ ID NO: 11, or to SEQ ID NO: 12. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the repetitive region of a B-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 1, or with SEQ ID NO: 10, or with SEQ ID NO: 11, or with SEQ ID NO: 12. Each possibility represents a separate embodiment of the invention.

The terms “homology” or “identity”, as used interchangeably herein, refer to sequence identity between two amino acid sequences or two nucleic acid sequences, with identity being a stricter comparison. The phrases “percent identity or homology” and “% identity or homology” refer to the percentage of sequence identity found in a comparison of two or more amino acid sequences or nucleic acid sequences. Two or more sequences can be anywhere from 0-100% identical, or any value there between. Identity can be determined by comparing a position in each sequence that can be aligned for purposes of comparison to a reference sequence. When a position in the compared sequence is occupied by the same nucleotide base or amino acid, then the molecules are identical at that position. A degree of identity of amino acid sequences is a function of the number of identical amino acids at positions shared by the amino acid sequences. A degree of identity between nucleic acid sequences is a function of the number of identical or matching nucleotides at positions shared by the nucleic acid sequences. A degree of homology of amino acid sequences is a function of the number of amino acids at positions shared by the polypeptide sequences.

The following is a non-limiting example for calculating homology or sequence identity between two sequences (the terms are used interchangeably herein). The sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in one or both of a first and a second amino acid or nucleic acid sequence for optimal alignment and non-homologous sequences can be disregarded for comparison purposes). The optimal alignment is determined as the best score using the GAP program in the GCG software package with a Blossum 62 scoring matrix with a gap penalty of 12, a gap extend penalty of 4, and a frame shift gap penalty of 5. The amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared. When a position in the first sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the second sequence, then the molecules are identical at that position. The percent identity between the two sequences is a function of the number of identical positions shared by the sequences.

In some embodiments, % homology or identity as described herein are calculated or determined using the basic local alignment search tool (BLAST). In some embodiments, % homology or identity as described herein are calculated or determined using Blossum 62 scoring matrix.

The term “nucleic acid” is well known in the art. A “nucleic acid” as used herein will generally refer to any molecule (e.g., a strand) of DNA, RNA or a derivative or analog thereof, comprising nucleotides. Nucleotides are comprised of nucleosides and phosphate groups. The nitrogenous bases of nucleosides include, for example, naturally occurring purine or pyrimidine nucleosides as found in DNA (e.g., an adenine “A,” a guanine “G,” a thymine “T” or a cytosine “C”) or RNA (e.g., an A, a G, an uracil “U” or a C).

The term “nucleic acid molecule” includes but is not limited to single-stranded RNA (ssRNA), double-stranded RNA (dsRNA), single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), small RNAs, circular nucleic acids, fragments of genomic DNA or RNA, degraded nucleic acids, amplification products, modified nucleic acids, plasmid or organellar nucleic acids, and artificial nucleic acids such as oligonucleotides.

In some embodiments n is an integer between 2 and 100, between 3 and 100, between 5 and 100, between 10 and 100, between 20 and 100, between 30 and 100, between 35 and 100, between 40 and 100, between 50 and 100, between 2 and 80, between 3 and 80, between 5 and 80, between 10 and 80, between 20 and 80, between 30 and 80, between 35 and 80, between 40 and 80, between 50 and 80, between 2 and 10, between 3 and 6, between 5 and 8, or between 10 and 15, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein (e.g. any one of SEQ ID NO: 1, SEQ ID NO: 11) further comprises an N-terminal region comprising the amino acid sequence: MSSRKGTRSSRIVTLERSANSSLSNNGGGDDSFGSTLLETSR (SEQ ID NO: 2) including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 2. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the N-terminal region of a B-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 2. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein (SEQ ID NO: 1) further comprises a C-terminal region comprising the amino acid sequence: GEEERLNLTQEAPQNTSVHHVSFSSGGASAQRGVKRRRVVDVNGEDQDIDYLNR RSKLNKETVGPVGIDEVDEEGKWVRVANNSEEEQSIGGYKLVVKAGNKEASFQF SSRMKLAPHASATVWSADAGAVHHPPEVYVMKKQQWPIGDNPSARLEDSEGDT VSSITVEFSESSDPSDPADRCSIM (SEQ ID NO: 3) including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the lamin-based protein (SEQ ID NO: 11) further comprises a C-terminal region comprising the amino acid sequence: NLTQEAPQNTSVHHVSFSSGGASAQRGVKRRRVVDVNGEDQDIDYLNRRSKLNK ETVGPVGIDEVDEEGKWVRVANNSEEEQSIGGYKLVVKAGNKEASFQFSSRMKL APHASATVWSADAGAVHHPPEVYVMKKQQWPIGDNPSARLEDSEGDTVSSITVE FSESSDPSDPADRCSIM (SEQ ID NO: 13) including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the lamin-based protein is a B-type lamin comprising the amino acid sequence of SEQ ID NO: 1, or SEQ ID NO: 11, and further comprising (i) a C-terminal region (comprising the amino acid sequence SEQ ID NO: 3); (ii) a N-terminal region (comprising the amino acid sequence SEQ ID NO: 2, or SEQ ID NO: 13) including any sequency homolog, or a functional homolog thereof; or both (i) and (ii).

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 3. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the C-terminal region of a B-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 3. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein is a B-type lamin comprising an amino acid sequence: MSSRKGTRSSRIVTLERSANSSLSNNGGGDDSFGSTLLETSRLQEKDHLTSLNSRL ATYIDKVRQLEQENNRLQVQIRDIEVVEKKEKSNLADRFEAEKARLRRALDSAQ DELAKYRIEYDAAKVEVKKLKPQVEKLERELAGAEEQALHAQSIADQSQAKQKT LQARNDKLVVENDDLKKQNITLRDTVEGLKKAVEDETLLRTAANNKIKALEEDL AFALQQHKGELEEVRHKRQVDMTTYAKQINDEYQSKLQDQIEEMRAQFKNNLH QNKTAFEDAYKNKLNAARERQEEAVSEAIHLRARVRDLETSSSGNASLIERLRSE LDTLKRSFQEKLDDKDARIAELNQEIERMMSEFHDLLDVKIQLDAELKTYQALLE GEEERLNLTQEAPQNTSVHHVSFSSGGASAQRGVKRRRVVDVNGEDQDIDYLNR RSKLNKETVGPVGIDEVDEEGKWVRVANNSEEEQSIGGYKLVVKAGNKEASFQF SSRMKLAPHASATVWSADAGAVHHPPEVYVMKKQQWPIGDNPSARLEDSEGDT VSSITVEFSESSDPSDPADRCSIM (SEQ ID NO: 10), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the fiber comprises an A-type lamin. In some embodiments, the fiber comprises an A-type lamin-based protein, wherein the fiber is characterized by a diameter between 1 μm and 200 μm, between 2 μm and 200 μm, between 3 μm and 200 μm, between 5 μm and 200 μm, between 7 μm and 200 μm, between 9 μm and 200 μm, between 1 μm and 190 μm, between 2 μm and 190 μm, between 3 μm and 190 μm, between 5 μm and 190 μm, between 7 μm and 190 μm, between 9 μm and 190 μm, 10 μm and 180 μm, between 15 μm and 180 μm, between 20 μm and 180 μm, between 25 μm and 180 μm, between 30 μm and 180 μm, between 50 μm and 180 μm, between 65 μm and 180 μm, between 10 μm and 100 μm, between 15 μm and 100 μm, between 20 μm and 100 μm, between 25 μm and 100 μm, between 30 μm and 100 μm, between 50 μm and 100 μm, between 65 μm and 100 μm, between 10 μm and 80 μm, between 15 μm and 80 μm, between 20 μm and 80 μm, between 25 μm and 80 μm, between 30 μm and 80 μm, between 50 μm and 80 μm, between 65 μm and 80 μm, between 10 μm and 50 μm, between 15 μm and 50 μm, between 20 μm and 50 μm, between 25 μm and 50 μm, or between 30 μm and 50 μm, including any range therebetween. Each possibility represents a separate embodiment of the invention. In some embodiments, the fiber is characterized by a length of at least 1 cm, at least 2 cm, at least 5 cm, at least 10 cm, at least 50 cm, at least 100 cm, at least 500 cm, at least 1000 cm, or at least 10000 cm, including any value therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the A-type lamin comprises n repeats of a repetitive region of a lamin protein comprising an amino acid sequence: LQEKEDLQELNDRLA VYIDR VRSLETENAGLRLRITESEEVVSREVSGIKAAYEAE LGDARKTLDSVAKERARLQLELSKVREEFKELKARNTKKEGDLIAAQARLKDLE ALLNSK(X₂)AALSTALSEKRTLEGELHDLRGQVAKLEAALGEAKKQLQDEMLRR VDAENRLQTMKEELDFQKNIYSEELRETKRRHETRLVEIDNGKQREFESRLADAL QELRAQHEDQVEQYKKELEKTYSAKLDNARQSAERNSNLVGAAHEELQQSRIRI DSLSAQLSQLQKQLAAKEAKLRDLEDSLARERDTSRRLLAEKEREMAEMRARM QQQLDEYQELLDIKLALDMEIHAYRKLLEGEEERL (SEQ ID NO: 4), including any functional analog having at least 70% sequence homology thereto. In some embodiments, X₂is Glu or Lys.

In some embodiments, the A-type lamin comprises n repeats of a repetitive region of a lamin protein comprising an amino acid sequence: LQEKEDLQELNDRLA VYIDR VRSLETENAGLRLRITESEEVVSREVSGIKAAYEAE LGDARKTLDSVAKERARLQLELSKVREEFKELKARNTKKEGDLIAAQARLKDLE ALLNSK(X₂)AALSTALSEKRTLEGELHDLRGQVAKLEAALGEAKKQLQDEMLRR VDAENRLQTMKEELDFQKNIYSEELRETKRRHETRLVEIDNGKQREFESRLADAL QELRAQHEDQVEQYKKELEKTYSAKLDNARQSAERNSNLVGAAHEELQQSRIRI DSLSAQLSQLQKQLAAKEAKLRDLEDSLARERDTSRRLLAEKEREMAEMRARM QQQLDEYQELLDIKLALDMEIHAYRKLLE (SEQ ID NO: 7), including any functional analog having at least 70% sequence homology thereto. In some embodiments, X₂is Glu or Lys.

In some embodiments n is an integer between 2 and 100, between 3 and 100, between 5 and 100, between 10 and 100, between 20 and 100, between 30 and 100, between 35 and 100, between 40 and 100, between 50 and 100, between 2 and 80, between 3 and 80, between 5 and 80, between 10 and 80, between 20 and 80, between 30 and 80, between 35 and 80, between 40 and 80, or between 50 and 80, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 4, or to SEQ ID NO: 7. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the repetitive region of a B-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 4, or with SEQ ID NO: 7. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein further comprises an N-terminal region comprising the amino acid sequence: METPSQRRATRSGAQASSTPLSPTRITR (SEQ ID NO: 5), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 5. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the N-terminal region of an A-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 5. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein further comprises a C-terminal region comprising the amino acid sequence: RLSPSPTSQRSRGRASSHSSQTQGGGSVTKKRKLESTESRSSFSQHARTSGRVAVE EVDEEGKFVRLRNKSNEDQSMGNWQIKRQNGDDPLLTYRFPPKFTLKAGQVVTI WAAGAGATHSPPTDLVWKAQNTWGCGNSLRTALINSTGEEVAMRKLVRSVTVV EDDEDEDGDDLLHHHHGSHCSSSGDPAEYNLRSRTVLCGTCGQPADKASASGSG AQVGGPISSGSSASSVTVTRSYRSVGGSGGGSFGDNLVTRSYLLGNSSPRTQSPQN CSIM (SEQ ID NO: 6), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the lamin-based protein further comprises a C-terminal region comprising the amino acid sequence: EEERLRLSPSPTSQRSRGRASSHSSQTQGGGSVTKKRKLESTESRSSFSQHARTSG RVAVEEVDEEGKFVRLRNKSNEDQSMGNWQIKRQNGDDPLLTYRFPPKFTLKAG QVVTIWAAGAGATHSPPTDLVWKAQNTWGCGNSLRTALINSTGEEVAMRKLVR SVTVVEDDEDEDGDDLLHHHHGSHCSSSGDPAEYNLRSRTVLCGTCGQPADKAS ASGSGAQVGGPISSGSSASSVTVTRSYRSVGGSGGGSFGDNLVTRSYLLGNSSPRT QSPQNCSIM (SEQ ID NO: 8), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, the functional analog comprises an amino acid sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 92%, at least 95%, at least 97%, at least 99%, or 100% homology or identity to SEQ ID NO: 6. Each possibility represents a separate embodiment of the invention. In some embodiments, there is provided a homolog of the C-terminal region of an A-type lamin protein sharing at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% homology with SEQ ID NO: 6, or with SEQ ID NO: 8. Each possibility represents a separate embodiment of the invention.

In some embodiments, the lamin-based protein is a A-type lamin comprising the amino acid sequence of SEQ ID NO: 4, or SEQ ID NO: 7, and further comprising (i) a C-terminal region (comprising the amino acid sequence SEQ ID NO: 6, or SEQ ID NO: 8); (ii) a N-terminal region (comprising the amino acid sequence SEQ ID NO: 5) including any sequency homolog, or a functional homolog thereof; or both (i) and (ii).

In some embodiments, the lamin-based protein of the invention comprises the repetitive region comprising an amino acid sequence selected from SEQ ID NOs: 1, 4, 7 or 10, or a functional analog comprising at least 70% at least 75%, at least 80%, at least 85%, at least 88% homology thereto, including any range between, wherein the lamin-based protein is an oligomer comprising at least 3, at least 4, at least 5, at least 6, at least 8, polypeptide monomers. In some embodiments, the lamin-based protein of the invention is an oligomer comprising between 4 and 8, between 4 and 6, between 6 and 8 or more polypeptide monomers. In some embodiments, each of the polypeptide monomers comprises an amino acid sequence selected from SEQ ID NOs: 1, 4, 7, or 9, and optionally one or more of the N-terminal amino acid sequence selected from SEQ ID NOs: 2 and 5; and C-terminal amino acid sequence selected from SEQ ID Nos: 6 and 8. In some embodiments, each of the polypeptide monomers comprises the same amino acid sequence. In some embodiments, at least one of the polypeptide monomers comprises a different amino acid sequence.

In some embodiments, the lamin-based protein is a A-type lamin comprising the amino acid sequence of METPSQRRATRSGAQASSTPLSPTRITRLQEKEDLQELNDRLAVYIDRVRSLETEN AGLRLRITESEEVVSREVSGIKAAYEAELGDARKTLDSVAKERARLQLELSKVRE EFKELKARNTKKEGDLIAAQARLKDLEALLNSKEAALSTALSEKRTLEGELHDLR GQVAKLEAALGEAKKQLQDEMLRRVDAENRLQTMKEELDFQKNIYSEELRETK RRHETRLVEIDNGKQREFESRLADALQELRAQHEDQVEQYKKELEKTYSAKLDN ARQSAERNSNLVGAAHEELQQSRIRIDSLSAQLSQLQKQLAAKEAKLRDLEDSLA RERDTSRRLLAEKEREMAEMRARMQQQLDEYQELLDIKLALDMEIHAYRKLLEG EEERLRLSPSPTSQRSRGRASSHSSQTQGGGSVTKKRKLESTESRSSFSQHARTSG RVAVEEVDEEGKFVRLRNKSNEDQSMGNWQIKRQNGDDPLLTYRFPPKFTLKAG QVVTIWAAGAGATHSPPTDLVWKAQNTWGCGNSLRTALINSTGEEVAMRKLVR SVTVVEDDEDEDGDDLLHHHHGSHCSSSGDPAEYNLRSRTVLCGTCGQPADKAS ASGSGAQVGGPISSGSSASSVTVTRSYRSVGGSGGGSFGDNLVTRSYLLGNSSPRT QSPQNCSIM (SEQ ID NO: 9), including any functional analog having at least 70% sequence homology thereto.

In some embodiments, a fiber comprising an A-type lamin as described hereinabove, further comprises a B-type lamin.

In some embodiments, the fiber of the invention comprises or is composed essentially of the lamin-based protein characterized by α-helix: β-sheet ratio between 5:1 and 1:1, between 4.55:1 and 1:1, between 4:1 and 1:1, between 3:1 and 1:1, between 2:1 and 1:1, between 5:1 and 3:1, between 4.55:1 and 3:1, between 4:1 and 3:1, between 5:1 and 2:1, between 4.55:1 and 2:1, between 4:1 and 2:1, or between 3:1 and 2:1, including any range therebetween, wherein α-helix: β-sheet ratio is determined by RAMAN. Each possibility represents a separate embodiment of the invention. Exemplary RAMAN-based determination of the α-helix: β-sheet ratio is described in Example 2. Additional method include FTIR and X-ray scattering.

In some embodiments, the fiber is a stretched fiber. In some embodiments, the stretched fiber is characterized by a relative content of the lamin-based protein in α-helix form ranging between about 30 and about 99%, between about 30 and about 45%, between about 30 and about 40%, including any range between. In some embodiments, the stretched fiber is characterized by a relative content of the lamin-based protein being in the β-sheet form ranging between 30 and 50%, between about 30 and about 45%, between about 30 and about 40%, between about 30 and about 80%, between about 30 and about 60%, between about 60 and about 99%, between about 40 and about 80%, between about 40 and about 90%, including any range between. The relative content of α-helix or β-sheet lamin-based protein is determined by RAMAN, relative to the total lamin-based protein content of the fiber, as described hereinbelow.

As used herein, the term “stretched fiber” refers to a fiber or filament that went through a stretching or drawing process. Stretching or drawing process refers to the process of pulling the long fiber or filament into alignment along its longitudinal axis. Stretching is usually performed up to a strain below fracture strain of the fibers, as disclosed hereinbelow (e.g. ranging between 100 and 400%, or between 100 and 1000%).

In some embodiments, the fiber of the invention comprises or is composed essentially of the lamin-based protein characterized by α-helix to β-sheet transition upon stretching the fiber in the elastic region. In some embodiments, the fiber of the invention comprises or is composed essentially of the lamin-based protein characterized by α-helix to β-sheet transition upon stretching the fiber to a strain of about 6%. In some embodiments, the α-helix to β-sheet transition comprises at least 10%, at least 20%, at least 30%, between 5 and 50%, between 10 and 50%, between 20 and 50%, between 20 and 40%, between 10 and 70%, between 10 and 60% transition, including any range between.

In some embodiments, the fiber of the invention comprises or is composed essentially of the lamin-based protein characterized by a α-helix to β-sheet transition between about 20% and about 90%, between about 20% and about 60%, between 20% and 50%, between 20% and 90%, between 3% and 50%, between 4% and 50%, between 5% and 50%, between 7% and 50%, between 10% and 50%, between 15% and 50%, between 20% and 50%, between 30% and 50%, between 3% and 40%, between 4% and 40%, between 5% and 40%, between 7% and 40%, between 10% and 40%, between 15% and 40%, between 20% and 40%, between 30% and 40%, between 3% and 25%, between 4% and 25%, between 5% and 25%, between 7% and 25%, between 10% and 25%, or between 15% and 25%, including any range therebetween. Each possibility represents a separate embodiment of the invention. The α-helix to β-sheet transition is determined by RAMAN after stretching the fiber. The α-helix to β-sheet transition refers to the change of the α-helix content of the fiber relative to the initial α-helix content before stretching. In some embodiments, the fiber of the invention undergoes α-helix to β-sheet transition in the elastic region. In some embodiments, the fiber of the invention undergoes α-helix to β-sheet transition (e.g. at least 10%, or at least 20% transition) upon stretching thereof to a strain of about 6%, about 10% or more, such as below fracture strain, between 5 and 1000%, between about 5 and about 100%, between about 5 and about 80% strain, including any range between.

In some embodiments, the stretched fiber of the invention comprises or is composed essentially of the lamin-based protein characterized by α-helix to β-sheet ratio between about 2:1 and about 1:1, including any range between, wherein the stretched fiber is characterized by a strain of between about 6 and about 100%, between about 6 and about 80%, between about 6 and about 50%, between about 6 and about 60%, between about 6 and about 70%, between about 6 and about 90%, including any range between.

In some embodiments, each repeat independently has a molecular weight in the range of 20 kDa to 80 kDa, 20 kDa to 70 kDa, 20 kDa to 60 kDa, 20 kDa to 55 kDa, or 20 kDa to 50 kDa, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, a fiber as described hereinabove comprises a plurality of the lamin-based protein arranged in a form of paracrystals. In some embodiments, each of the paracrystals is characterized by a dimension selected from: (i) a width between 1 nm and 500 nm; (ii) a length between 0.5 mm and 1 cm, or both (i) and (ii).

In some embodiments, each of the paracrystals is characterized by a width between 1 nm and 500 nm, between 2 nm and 500 nm, between 5 nm and 500 nm, between 15 nm and 500 nm, between 50 nm and 500 nm, between 100 nm and 500 nm, between 250 nm and 500 nm, between 1 nm and 300 nm, between 2 nm and 300 nm, between 5 nm and 300 nm, between 15 nm and 300 nm, between 50 nm and 300 nm, between 100 nm and 300 nm, between 1 nm and 100 nm, between 2 nm and 100 nm, between 5 nm and 100 nm, between 15 nm and 100 nm, or between 50 nm and 100 nm, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, each of the paracrystals is characterized by a length between 0.5 mm and 1 cm, between 0.7 mm and 1 cm, between 0.9 mm and 1 cm, between 1 mm and 1 cm, between 10 mm and 1 cm, between 30 mm and 1 cm, between 50 mm and 1 cm, between 100 mm and 1 cm, between 500 mm and 1 cm, between 700 mm and 1 cm, between 0.5 mm and 900 mm, between 0.7 mm and 900 mm, between 0.9 mm and 900 mm, between 1 mm and 900 mm, between 10 mm and 900 mm, between 30 mm and 900 mm, between 50 mm and 900 mm, between 100 mm and 900 mm, between 500 mm and 900 mm, between 700 mm and 900 mm, between 0.5 mm and 500 mm, between 0.7 mm and 500 mm, between 0.9 mm and 500 mm, between 1 mm and 500 mm, between 10 mm and 500 mm, between 30 mm and 500 mm, between 50 mm and 500 mm, or between 100 mm and 500 mm, including any range therebetween. Each possibility represents a separate embodiment of the invention.

As used herein, the term “paracrystal” refers to a nanofilament (obtained upon association of tetrameric protofilaments), wherein the nanofilaments are unidirectional nanofilaments, aligned along the longitudinal axis of the fiber. As used herein, “protofilament” refers to structures formed by the polymerization of lamin dimers. In some embodiments, the polymers of dimers are associated to form tetrameric protofilaments.

In some embodiments, the lamin-based protein is assembled within the fiber of the invention in a form of lamin dimers. In some embodiments, the lamin-based protein is assembled within the fiber of the invention in a form of protofilaments. In some embodiments, the protofilaments are essentially unidirectionally aligned within the fiber. In some embodiments, the protofilaments aligned along the longitudinal axis of the fiber. In some embodiments, each protofilament comprises a plurality of lamin dimers (e.g. a polymer comprising a plurality of lamin dimers). In some embodiments, the lamin-based protein is assembled within the fiber of the invention in a form of tetrameric protofilaments. In some embodiments, the lamin-based protein is assembled within the fiber of the invention in a form of paracrystals (or nanofilaments) comprising tetrameric protofilaments.

In some embodiments, the lamin-based protein is an isolated protein.

As used herein, the terms “isolated protein” refers to a protein that is essentially free from contaminating cellular components, such as carbohydrate, lipid, or other proteinaceous impurities associated with the nucleic acid in nature. Typically, a preparation of an isolated protein contains the protein in a highly purified form, e.g., at least about 80% pure, at least about 90% pure, at least about 95% pure, greater than 95% pure, or greater than 99% pure. In some embodiments, the isolated protein is a synthesized protein. Synthesis of protein is well known in the art and may be performed, for example, by heterologous expression in a transformed cell, such as exemplified herein.

In some embodiments, the lamin-based protein is a recombinant protein. In some embodiments, the fiber is obtained by expression in a recombinant cell. In some embodiments, the fiber is obtained by expression in a bacterium. In some embodiments, the bacterium is Escherichia coli.

According to some embodiments, there is provided an artificial nucleic acid molecule comprising the polynucleotide disclosed herein (i.e. SEQ ID No: 14, and SEQ ID NO: 15). In some embodiments, the artificial nucleic acid molecule comprises a polynucleotide sequence of: ATGTCATCTCGTAAAGGTACTCGTAGTTCTCGTATTGTTACGCTAGAGCGCTC AGCGAATTCGTCGCTAAGCAACAATGGAGGAGGCGACGATTCATTTGGCTCA ACGCTTCTAGAAACTTCACGTCTTCAAGAGAAAGATCATTTGACTTCACTCAA CAGTCGTCTTGCCACTTACATCGACAAAGTTCGTCAATTGGAGCAAGAGAAC AACAGACTCCAGGTTCAAATTCGCGACATCGAAGTTGTTGAAAAGAAAGAGA AGTCAAACTTGGCCGATCGCTTCGAGGCGGAAAAGGCTCGTCTCCGTCGTGCC CTCGATTCGGCTCAAGATGAGCTCGCAAAATACAGGATCGAGTATGACGCTG CAAAGGTTGAAGTAAAGAAGTTGAAGCCACAAGTCGAAAAACTTGAGAGAG AACTCGCTGGAGCTGAGGAACAAGCCCTCCATGCCCAATCTATTGCTGATCAA AGTCAAGCAAAACAGAAGACGTTGCAGGCACGCAACGATAAATTGGTGGTGG AGAATGATGATCTCAAAAAGCAGAACATCACTCTTCGTGACACCGTAGAAGG ACTCAAGAAAGCCGTTGAAGATGAAACTCTTCTCCGAACAGCCGCCAACAAT AAAATCAAGGCTCTGGAAGAAGATCTCGCTTTTGCTCTTCAACAGCACAAGG GAGAACTTGAAGAAGTTCGTCACAAGAGACAGGTCGACATGACAACCTACGC CAAGCAGATTAATGATGAGTATCAATCTAAGCTTCAAGATCAAATCGAAGAG ATGCGTGCTCAGTTCAAGAACAATTTGCATCAAAACAAAACAGCTTTCGAAG ATGCCTACAAAAACAAGCTCAATGCTGCTCGTGAACGCCAAGAGGAGGCTGT ATCCGAAGCAATCCATCTTCGTGCCCGTGTTCGTGACTTGGAGACATCAAGCA GTGGAAATGCTTCGCTCATCGAACGTCTTCGTTCAGAGCTCGACACTCTGAAG AGATCGTTCCAAGAGAAGCTCGACGACAAGGATGCTCGAATTGCTGAACTTA ATCAAGAGATCGAGCGCATGATGAGCGAGTTCCACGATCTTCTTGATGTTAAA ATCCAATTGGACGCCGAACTCAAGACCTACCAAGCTCTCCTTGAGGGTGAGG AGGAGCGTCTCAATCTTACTCAGGAGGCGCCACAAAACACTTCAGTTCATCAC GTCTCGTTTTCATCCGGAGGAGCAAGCGCTCAGCGCGGAGTGAAGCGTCGTC GCGTTGTCGATGTAAATGGAGAGGACCAAGACATTGATTATCTCAACCGTCG CTCCAAACTCAACAAAGAGACTGTTGGCCCAGTTGGAATCGACGAGGTTGAT GAGGAAGGAAAGTGGGTCCGTGTTGCAAACAACTCTGAAGAAGAACAATCCA TCGGAGGATACAAGTTGGTGGTCAAAGCTGGAAACAAAGAAGCCTCCTTCCA ATTTTCATCTCGTATGAAGCTCGCTCCACATGCTAGCGCCACCGTTTGGTCTGC GGATGCTGGTGCCGTTCACCACCCACCAGAAGTCTACGTTATGAAGAAGCAA CAGTGGCCAATTGGAGATAACCCATCAGCTCGTCTTGAGGATAGTGAAGGAG ACACTGTTTCTTCTATCACCGTTGAATTCAGCGAATCATCGGATCCATCGGAC CCAGCCGATCGTTGTTCCATCATGTAA (SEQ ID NO: 14), corresponding to a portion of the B-type lamin of SEQ ID NO: 10.

In some embodiments, the artificial nucleic acid molecule comprises a polynucleotide sequence of: ATGGAGACCCCGTCCCAGCGGCGCGCCACCCGCAGCGGGGCGCAGGCCAGCT CCACTCCGCTGTCGCCCACCCGCATCACCCGGCTGCAGGAGAAGGAGGACCT GCAGGAGCTCAATGATCGCTTGGCGGTCTACATCGACCGTGTGCGCTCGCTGG AAACGGAGAACGCAGGGCTGCGCCTTCGCATCACCGAGTCTGAAGAGGTGGT CAGCCGCGAGGTGTCCGGCATCAAGGCCGCCTACGAGGCCGAGCTCGGGGAT GCCCGCAAGACCCTTGACTCAGTAGCCAAGGAGCGCGCCCGCCTGCAGCTGG AGCTGAGCAAAGTGCGTGAGGAGTTTAAGGAGCTGAAAGCGCGCAATACCAA GAAGGAGGGTGACCTGATAGCTGCTCAGGCTCGGCTGAAGGACCTGGAGGCT CTGCTGAACTCCAAGGAGGCCGCACTGAGCACTGCTCTCAGTGAGAAGCGCA CGCTGGAGGGCGAGCTGCATGATCTGCGGGGCCAGGTGGCCAAGCTTGAGGC AGCCCTAGGTGAGGCCAAGAAGCAACTTCAGGATGAGATGCTGCGGCGGGTG GATGCTGAGAACAGGCTGCAGACCATGAAGGAGGAACTGGACTTCCAGAAG AACATCTACAGTGAGGAGCTGCGTGAGACCAAGCGCCGTCATGAGACCCGAC TGGTGGAGATTGACAATGGGAAGCAGCGTGAGTTTGAGAGCCGGCTGGCGGA TGCGCTGCAGGAACTGCGGGCCCAGCATGAGGACCAGGTGGAGCAGTATAAG AAGGAGCTGGAGAAGACTTATTCTGCCAAGCTGGACAATGCCAGGCAGTCTG CTGAGAGGAACAGCAACCTGGTGGGGGCTGCCCACGAGGAGCTGCAGCAGTC GCGCATCCGCATCGACAGCCTCTCTGCCCAGCTCAGCCAGCTCCAGAAGCAG CTGGCAGCCAAGGAGGCGAAGCTTCGAGACCTGGAGGACTCACTGGCCCGTG AGCGGGACACCAGCCGGCGGCTGCTGGCGGAAAAGGAGCGGGAGATGGCCG AGATGCGGGCAAGGATGCAGCAGCAGCTGGACGAGTACCAGGAGCTTCTGGA CATCAAGCTGGCCCTGGACATGGAGATCCACGCCTACCGCAAGCTCTTGGAG GGCGAGGAGGAGAGGCTACGCCTGTCCCCCAGCCCTACCTCGCAGCGCAGCC GTGGCCGTGCTTCCTCTCACTCATCCCAGACACAGGGTGGGGGCAGCGTCACC AAAAAGCGCAAACTGGAGTCCACTGAGAGCCGCAGCAGCTTCTCACAGCACG CACGCACTAGCGGGCGCGTGGCCGTGGAGGAGGTGGATGAGGAGGGCAAGT TTGTCCGGCTGCGCAACAAGTCCAATGAGGACCAGTCCATGGGCAATTGGCA GATCAAGCGCCAGAATGGAGATGATCCCTTGCTGACTTACCGGTTCCCACCAA AGTTCACCCTGAAGGCTGGGCAGGTGGTGACGATCTGGGCTGCAGGAGCTGG GGCCACCCACAGCCCCCCTACCGACCTGGTGTGGAAGGCACAGAACACCTGG GGCTGCGGGAACAGCCTGCGTACGGCTCTCATCAACTCCACTGGGGAAGAAG TGGCCATGCGCAAGCTGGTGCGCTCAGTGACTGTGGTTGAGGACGACGAGGA TGAGGATGGAGATGACCTGCTCCATCACCACCACGGCTCCCACTGCAGCAGC TCGGGGGACCCCGCTGAGTACAACCTGCGCTCGCGCACCGTGCTGTGCGGGA CCTGCGGGCAGCCTGCCGACAAGGCATCTGCCAGCGGCTCAGGAGCCCAGGT GGGCGGACCCATCTCCTCTGGCTCTTCTGCCTCCAGTGTCACGGTCACTCGCA GCTACCGCAGTGTGGGGGGCAGTGGGGGTGGCAGCTTCGGGGACAATCTGGT CACCCGCTCCTACCTCCTGGGCAACTCCAGCCCCCGAACCCAGAGCCCCCAGA ACTGCAGCATCATGTAA (SEQ ID NO: 15), corresponding to the A-type lamin of SEQ ID NO: 9.

In some embodiments, the artificial vector comprises a plasmid. In some embodiments, the artificial vector comprises or is an agrobacterium comprising the artificial nucleic acid molecule. In some embodiments, the artificial vector is an expression vector. In some embodiments, the artificial vector is a plant expression vector. In some embodiments, the artificial vector is for use in expressing an AAE encoding nucleic acid sequence as disclosed herein. In some embodiments, the artificial vector is for use in heterologous expression of an AAE encoding nucleic acid sequence as disclosed herein in a cell, a tissue, or an organism. In some embodiments, the artificial vector is for use in producing or the production of an acyl-coenzyme A (acyl-CoA) in a cell, a tissue, or an organism.

Expressing of a polynucleotide within a cell is well known to one skilled in the art. It can be carried out by, among many methods, transfection, viral infection, or direct alteration of the cell's genome. In some embodiments, the polynucleotide is in an expression vector such as plasmid or viral vector. A vector nucleic acid sequence generally contains at least an origin of replication for propagation in a cell and optionally additional elements, such as a heterologous polynucleotide sequence, expression control element (e.g., a promoter, enhancer), selectable marker (e.g., antibiotic resistance), poly-Adenine sequence.

The vector may be a DNA plasmid delivered via non-viral methods or via viral methods. The viral vector may be a retroviral vector, a herpes viral vector, an adenoviral vector, an adeno-associated viral vector, a veralipride viral vector, or a poxviral vector. The barley stripe mosaic virus (BSMV), the tobacco rattle virus and the cabbage leaf curl geminivirus (CbLCV) may also be used. The promoters may be active in plant cells. The promoters may be a viral promoter.

In some embodiments, the polynucleotide as disclosed herein is operably linked to a promoter. The term “operably linked” is intended to mean that the nucleotide sequence of interest is linked to the regulatory element or elements in a manner that allows for expression of the nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell). In some embodiments, the promoter is operably linked to the polynucleotide of the invention. In some embodiments, the promoter is a heterologous promoter. In some embodiments, the promoter is the endogenous promoter.

In some embodiments, the vector is introduced into the cell by standard methods including electroporation (e.g., as described in From et al., Proc. Natl. Acad. Sci. USA 82, 5824 (1985)), heat shock, infection by viral vectors, high velocity ballistic penetration by small particles with the nucleic acid either within the matrix of small beads or particles, or on the surface (Klein et al., Nature 327. 70-73 (1987)), such as biolistic use of coated particles, and needle-like particles, Agrobacterium Ti plasmids and/or the like.

The term “promoter” as used herein refers to a group of transcriptional control modules that are clustered around the initiation site for an RNA polymerase i.e., RNA polymerase II. Promoters are composed of discrete functional modules, each consisting of approximately 7-20 bp of DNA, and containing one or more recognition sites for transcriptional activator or repressor proteins. The promoter may extend upstream or downstream of the transcriptional start site and may be any size ranging from a few base pairs to several kilo-bases.

In some embodiments, the polynucleotide is transcribed by RNA polymerase II (RNAP II and Pol II). RNAP II is an enzyme found in eukaryotic cells, known to catalyze the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA.

In some embodiments, recombinant viral vectors, which offer advantages such as systemic infection and targeting specificity, are used for in vivo expression. In one embodiment, systemic infection is inherent in the life cycle of, for example, the retrovirus and is the process by which a single infected cell produces many progeny virions that infect neighboring cells. In one embodiment, the result is that a large area becomes rapidly infected, most of which was not initially infected by the original viral particles. In one embodiment, viral vectors are produced that are unable to spread systemically. In one embodiment, this characteristic can be useful if the desired purpose is to introduce a specified gene into only a localized number of targeted cells.

In some embodiments, plant viral vectors are used. In some embodiments, a wild-type virus is used. In some embodiments, a deconstructed virus such as are known in the art is used. In some embodiments, Agrobacterium is used to introduce the vector of the invention into a virus.

In some embodiments, expression vectors containing regulatory elements from eukaryotic viruses such as retroviruses are used by the present invention. SV40 vectors include pSVT7 and pMT2. In some embodiments, vectors derived from bovine papilloma virus include pBV-1MTHA, and vectors derived from Epstein Bar virus include pHEBO, and p2O5. Other exemplary vectors include pMSG, pAV009/A+, pMTO10/A+, pMAMneo-5, baculovirus pDSVE, and any other vector allowing expression of proteins under the direction of the SV-40 early promoter, SV-40 later promoter, metallothionein promoter, murine mammary tumor virus promoter, Rous sarcoma virus promoter, polyhedrin promoter, or other promoters shown effective for expression in eukaryotic cells.

Various methods can be used to introduce the expression vector of the present invention into cells. Such methods are generally described in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Springs Harbor Laboratory, New York (1989, 1992), in Ausubel et al., Current Protocols in Molecular Biology, John Wiley and Sons, Baltimore, Md. (1989), Chang et al., Somatic Gene Therapy, CRC Press, Ann Arbor, Mich. (1995), Vega et al., Gene Targeting, CRC Press, Ann Arbor Mich. (1995), Vectors: A Survey of Molecular Cloning Vectors and Their Uses, Butterworths, Boston Mass. (1988) and Gilboa et at. [Biotechniques 4 (6): 504-512, 1986] and include, for example, stable or transient transfection, lipofection, electroporation and infection with recombinant viral vectors. In addition, see U.S. Pat. Nos. 5,464,764 and 5,487,992 for positive-negative selection methods.

In one embodiment, plant expression vectors are used. In one embodiment, the expression of a polypeptide coding sequence is driven by a number of promoters. In some embodiments, viral promoters such as the 35S RNA and 19S RNA promoters of CaMV [Brisson et al., Nature 310:511-514 (1984)], or the coat protein promoter to TMV [Takamatsu et al., EMBO J. 6:307-311 (1987)] are used. In another embodiment, plant promoters are used such as, for example, the small subunit of RUBISCO [Coruzzi et al., EMBO J. 3:1671-1680 (1984); and Brogli et al., Science 224:838-843 (1984)] or heat shock promoters, e.g., soybean hsp17.5-E or hsp17.3-B [Gurley et al., Mol. Cell. Biol. 6:559-565 (1986)]. In one embodiment, constructs are introduced into plant cells using Ti plasmid, Ri plasmid, plant viral vectors, direct DNA transformation, microinjection, electroporation and other techniques well known to the skilled artisan. See, for example, Weissbach & Weissbach [Methods for Plant Molecular Biology, Academic Press, NY, Section VIII, pp 421-463 (1988)]. Other expression systems such as insects and mammalian host cell systems, which are well known in the art, can also be used by the present invention.

It will be appreciated that other than containing the necessary elements for the transcription and translation of the inserted coding sequence (encoding the polypeptide), the expression construct of the present invention can also include sequences engineered to optimize stability, production, purification, yield, or activity of the expressed polypeptide.

In some embodiments, the artificial vector comprises a polynucleotide encoding a protein comprising an amino acid sequence as described herein.

In some embodiments, the lamin-based protein is an isolated protein.

In some embodiments, the fiber of the invention further comprises a coating. In some embodiments, the lamin-based protein fiber comprising a coating is referred to herein as a “coated fiber”. In some embodiments, the fiber of the invention is a coated fiber.

In some embodiments, the coated fiber comprises the lamin-based protein fiber of the invention in contact with a coating. In some embodiments, the surface of the fiber is in contact with the coating. In some embodiments, the outer surface of the lamin-based protein fiber is in contact with the coating. In some embodiments, at least a portion (i.e. at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99%, at least 99.9%, at most 90%, at most 100%, at most 95%, at most 97%) of the lamin-based protein fiber surface is in contact with the coating.

In some embodiments, the term “in contact with” encompasses that the lamin-based protein fiber (e.g. the outer portion of the fiber) is bound to the coating via a non-covalent bond (e.g. including a physical bond or interaction). In some embodiments, bound is via a physisorption. In some embodiments, the coating is adsorbed to the lamin-based protein fiber. In some embodiments, the coating is embedded within at least a portion of the lamin-based protein fiber. In some embodiments, the coated fiber comprises the lamin-based protein fiber of the invention stably bound to the coating.

As used herein the term “stably bound” refers to the ability of the coated fiber to substantially maintain its structural, physical and/or chemical properties upon storage thereof under suitable conditions for a time period ranging up to 1 month, up to 1 year, up to 3 years, or up to 10 years, or more, including any range between. In some embodiments, the fiber of the invention is referred to as stable, when it substantially maintains its structure (e.g., shape, and/or a dimension such as thickness, length, etc.). In some embodiments, substantially is as described herein. In some embodiments, suitable conditions comprises exposure to the ambient atmosphere, UV/Vis light radiation and/or to a temperature of between-50 and 70° C., between-50 and 60° C., between-50 and 50° C., between-50 and 0° C., between 0 and 10° C., between 10 and 30° C., between 3° and 50° C., between 5° and 70° C., between 7° and 100° C., any range therebetween.

In some embodiments, the coated fiber is referred to as stable, when it is substantially devoid of disintegration, cracks, deformations, or any other surface irregularities or defects in the entire composition or physical structure of the coated fiber.

In some embodiments, the coating is in a form of a coating layer. In some embodiments, the terms “coating” and “coating layer” are used herein interchangeably.

In some embodiments, the coating is in a form of a film. In some embodiments, the coating forms a substantially uniform layer on top of the lamin-based protein fiber. In some embodiments, the coating layer is a uniform layer.

By “uniform” or “homogenous” when referring to the layer or film, it is meant to refer to size (or thickness) distribution that varies within a range of less than e.g., ±50%, ±40%, ±30%, ±20%, ±10%, ±5%, or less including any value therebetween.

In some embodiments, the term “layer”, refers to a substantially uniform thickness of a substantially homogeneous substance. In some embodiments, the layer or film comprises a single layer, or a plurality of layers. In some embodiments, the term layer and the term film are used herein interchangeably.

In some embodiments, the coating (or a coating layer) is at least 1 nm, at least 10 nm, at least 5 nm, at least 50 nm, at least 100 nm, at least 500 nm, at least 1 μm, at least 5 μm, at least 10 μm, at least 50 μm, including any range between. In some embodiments, the coating (or a coating layer) is characterized by a thickness of between about 1 nm and about 50 μm, between about 1 nm and about 50 μm, between about 1 nm and about 30 μm, between about 1 nm and about 20 μm, between about 1 nm and about 10 μm, between about 1 nm and about 1 μm, between about 1 nm and about 0.1 μm, between about 10 nm and about 50 μm, between about 10 nm and about 5 μm, between about 10 nm and about 1 μm, between about 10 nm and about 0.1 μm, between about 1 nm and about 500 nm, between about 1 nm and about 100 nm, between about 10 and about 1000 μm, between about 100 nm and about 10 μm, between about 10 and about 50 μm, including any range between. The term “thick and “thickness” refer to an average value.

In some embodiments, the coating comprises a film former. In some embodiments, the coating is a hydrophobic coating. In some embodiments, the hydrophobic coating comprises or consist essentially of a water immiscible compound. In some embodiments, the water immiscible compound is configured to form a stable film on top of the lamin-based protein fiber. In some embodiments, the water immiscible compound is a water immiscible small molecule, or a water immiscible polymer.

In some embodiments, the coating comprises a vegetable oil, a mineral oil, fatty acids, isobutyl-stearate, tallow fatty acid 2-ethylhexyl ester, polyol carboxylic acid ester, coconut oil fatty acid ester of glycerol, alkoxylated glycerol, a silicone, dimethyl polysiloxane, a polyalkylene glycol, polyethylene oxide, and a propylene oxide copolymer, including any salt, any combination, and any copolymer thereof.

In some embodiments, the hydrophobic coating is selected from an oil, a fat, a fatty acid, a fatty acid ester, a fatty alcohol, a glyceride (e.g. mono-, di-, and/or tri-glyceride), a phospholipid, a lipid, a solid lipid, a vegetable oil, essential oil, a plant oil, isobutyl-stearate, tallow fatty acid 2-ethylhexyl ester, polyol carboxylic acid ester, a glyceride, coconut oil fatty acid ester of glycerol, alkoxylated glycerol, a silicone oil, a mineral oil, dimethyl polysiloxane, a polysiloxane, a polysilane, and a wax, including any salt, any combination, and any copolymer thereof.

According to an aspect of some embodiments of the present invention there is provided a fiber as described hereinabove, wherein the fiber is characterized by at least one mechanical property selected from: Yield strength between 1 MPa and 1000 MPa; tensile strength between 1 MPa and 1000 MPa; fracture strain between 10% and 500%; toughness between 30 MJ/m³and 1000 MJ/m³; and a Young's Modulus between 0.001 GPa and 30 GPa.

In some embodiments, the fiber of the invention is characterized by a Yield strength between 1 MPa and 1000 MPa, between 5 MPa and 1000 MPa, between 10 MPa and 1000 MPa, between 20 MPa and 1000 MPa, between 30 MPa and 1000 MPa, between 50 MPa and 1000 MPa, between 70 MPa and 1000 MPa, between 100 MPa and 1000 MPa, between 250 MPa and 1000 MPa, between 300 MPa and 1000 MPa, between 500 MPa and 1000 MPa, 1 MPa and 700 MPa, between 5 MPa and 700 MPa, between 10 MPa and 700 MPa, between 20 MPa and 700 MPa, between 30 MPa and 700 MPa, between 50 MPa and 700 MPa, between 70 MPa and 700 MPa, between 100 MPa and 700 MPa, between 250 MPa and 700 MPa, between 300 MPa and 700 MPa, between 500 MPa and 700 MPa, between 1 MPa and 300 MPa, between 5 MPa and 300 MPa, between 10 MPa and 300 MPa, between 20 MPa and 300 MPa, between 30 MPa and 300 MPa, between 50 MPa and 300 MPa, between 70 MPa and 300 MPa, or between 100 MPa and 300 MPa, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the fiber of the invention is characterized by a tensile strength between 1 MPa and 1000 MPa, between 5 MPa and 1000 MPa, between 10 MPa and 1000 MPa, between 20 MPa and 1000 MPa, between 30 MPa and 1000 MPa, between 50 MPa and 1000 MPa, between 70 MPa and 1000 MPa, between 100 MPa and 1000 MPa, between 250 MPa and 1000 MPa, between 300 MPa and 1000 MPa, between 500 MPa and 1000 MPa, 1 MPa and 700 MPa, between 5 MPa and 700 MPa, between 10 MPa and 700 MPa, between 20 MPa and 700 MPa, between 30 MPa and 700 MPa, between 50 MPa and 700 MPa, between 70 MPa and 700 MPa, between 100 MPa and 700 MPa, between 250 MPa and 700 MPa, between 300 MPa and 700 MPa, between 500 MPa and 700 MPa, between 1 MPa and 300 MPa, between 5 MPa and 300 MPa, between 10 MPa and 300 MPa, between 20 MPa and 300 MPa, between 30 MPa and 300 MPa, between 50 MPa and 300 MPa, between 70 MPa and 300 MPa, or between 100 MPa and 300 MPa, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the fiber of the invention is characterized by a fracture strain between 10% and 500%, between 20% and 500%, between 50% and 500%, between 90% and 500%, between 100% and 500%, between 250% and 500%, between 10% and 350%, between 20% and 350%, between 50% and 350%, between 90% and 350%, between 100% and 350%, between 250% and 350%, between 50 and 1000%, between about 100 and about 1000%, between about 100 and about 800%, between about 100 and about 400%, between about 100 and about 500%, between about 100 and about 600%, between about 100 and about 700%, between about 100 and about 900%, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the fiber of the invention is characterized by a toughness between 30 MJ/m³and 1000 MJ/m³, between 50 MJ/m³and 1000 MJ/m³, between 70 MJ/m³and 1000 MJ/m³, between 100 MJ/m³and 1000 MJ/m³, between 300 MJ/m³and 1000 MJ/m³, between 500 MJ/m³and 1000 MJ/m³, between 700 MJ/m³and 1000 MJ/m³, between 30 MJ/m³and 700 MJ/m³, between 50 MJ/m³and 700 MJ/m³, between 70 MJ/m³and 700 MJ/m³, between 100 MJ/m³and 700 MJ/m³, between 300 MJ/m³and 700 MJ/m³, between 500 MJ/m³and 700 MJ/m³, between 30 MJ/m³and 500 MJ/m³, between 50 MJ/m³and 500 MJ/m³, between 70 MJ/m³and 500 MJ/m³, between 100 MJ/m³and 500 MJ/m³, or between 300 MJ/m³and 500 MJ/m³, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the fiber of the invention is characterized by a Young's Modulus between 0.001 GPa and 30 GPa, between 0.005 GPa and 30 GPa, between 0.009 GPa and 30 GPa, between 0.01 GPa and 30 GPa, between 0.05 GPa and 30 GPa, between 0.1 GPa and 30 GPa, between 1 GPa and 30 GPa, between 10 GPa and 30 GPa, between 0.001 GPa and 20 GPa, between 0.005 GPa and 20 GPa, between 0.009 GPa and 20 GPa, between 0.01 GPa and 20 GPa, between 0.05 GPa and 20 GPa, between 0.1 GPa and 20 GPa, between 1 GPa and 20 GPa, between 10 GPa and 20 GPa, between 0.001 GPa and 10 GPa, between 0.005 GPa and 10 GPa, between 0.009 GPa and 10 GPa, between 0.01 GPa and 10 GPa, between 0.05 GPa and 10 GPa, between 0.1 GPa and 10 GPa, or between 1 GPa and 10 GPa, including any range therebetween. Each possibility represents a separate embodiment of the invention. The above mentioned physical properties encompass any of the fibers disclosed herein, including the lamin-protein based fiber, and the coated fiber.

According to an aspect of some embodiments of the present invention there is provided a fiber comprising a B-type lamin-based protein, the fiber is characterized by a (i) diameter between 10 μm and 180 μm; and (ii) the B-type lamin-based protein comprises an amino acid as set forth in SEQ ID NO: 1, or in SEQ ID NO: 11, including any functional analog having at least 70% sequence homology thereto; wherein: if X₁is Gln, than the fiber is characterized by any of: (i) a residual amount of an alcohol; (ii) toughness of greater than 190 MJ/m³and (ii) the protein is characterized by a α-helix to β-sheet transition upon stretching between 3% and 50%, upon stretching thereof. In some embodiments, the fiber further comprises any of: i. an N-terminal region comprising the amino acid sequence SEQ ID NO: 2 or any functional analog having at least 70% sequence homology thereto; ii. a C-terminal region comprising the amino acid sequence SEQ ID NO: 3 or any functional analog having at least 70% sequence homology thereto.

In some embodiments, a fiber of the invention as described hereinabove is characterized by a toughness of greater than 195 MJ/m³, greater than 200 MJ/m³, greater than 205 MJ/m³, greater than 250 MJ/m³, greater than 270 MJ/m³, greater than 290 MJ/m³, greater than 300 MJ/m³, greater than 500 MJ/m³, or greater than 700 MJ/m³, including any value therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, a fiber as described hereinabove is for use in biological materials (biomaterials) and biomimetic materials.

In some embodiments, a fiber as described hereinabove is for use in the field of regenerative medicine, for example, in the manufacture of scaffolds suitable for tissue engineering and tissue graft production.

In some embodiments, a fiber as described hereinabove is for use in the manufacture of wound closure or coverage systems, for example, in the manufacture of suture materials, and wound dressings.

In some embodiments, a fiber as described hereinabove is for use in medical devices, such as medical adhesive strips, skin grafts, replacement ligaments, surgical mesh, membranes, and filters.

In some embodiments, a fiber as described hereinabove is for use in cosmetics and drug delivery.

In some embodiments, a fiber as described hereinabove is for use in a wide range of industrial and commercial products, such as films (e.g. transparent films), clothing fabric, bullet-proof vest lining, container fabric, bag or purse straps, cable, rope, adhesive binding material, non-adhesive binding material, strapping material, automotive covers and parts, aircraft construction material, weatherproofing material, flexible partition material, and sports equipment.

In some embodiments, a fiber as described hereinabove is for use in a coating, for example, a coating for textile and leather products, thereby conferring stability and durability to the coated product, or ordering additional properties to the coated product, such as water repellency, etc.

In some embodiments, a fiber as described hereinabove may be combined with other materials for the production of products or articles. In some embodiments, a fiber as described hereinabove may be combined with other materials to obtain a composite. In some embodiments, the composite is stable, wherein the term “stable” is as described herein. In some embodiments, there is provided a composite comprising the fibers of the invention and an additional polymer. In some embodiments, the composite further comprises an additive, such as binder, cross-linking agent, plasticizer, stabilizer, filler, etc. In some embodiments, the polymeric content of the composite is composed essentially of the fibers of the invention and the additional polymer. In some embodiments, between 50 and 99%, between 50 and 95%, between 50 and 90%, between 50 and 80%, between 50 and 70% by weight of the polymeric content of the composite is composed of the fibers of the invention and the additional polymer. In some embodiments, additional polymer forms a matrix of the composite, and the fibers of the invention provide a mechanical reinforcement to the matrix. In some embodiments, the additional polymer is compatible with the fibers of the invention, so as to obtain a stable composite.

In some embodiments, the composite comprises between 1 and 50%, between 1 and 30%, between 1 and 10%, between 1 and 20%, between 10 and 50%, between 20 and 50%, between 30 and 50%, between 10 and 60%, between 10 and 70% w/w of the fiber of the invention, and further comprises the additional polymer. In some embodiments, the additional polymer is transparent (e.g. between 70 and 100% light transparency). In some embodiments, the additional polymer comprises a synthetic polymer comprising a thermoplastic polymer or a thermoset polymer. In some embodiments, the synthetic polymer is a non-biodegradable polymer. In some embodiments, the synthetic polymer is a biodegradable polymer. In some embodiments, the synthetic polymer is a crosslinked polymer (also referred to herein as a “cured polymer”).

In some embodiments, the additional polymer comprises a cured resin. Examples of suitable resins include but are not limited to an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, methacrylate resin (e.g. including acrylate and esterified acrylates or other acrylate based resins), fluorocarbon resin, and a phenol resin, or any combination thereof.

In some embodiments, the additional polymer comprises a polyolefin (e.g. a polyethylene, polypropylene), polyester, polystyrene, C1-C8 alkyl styrene, polyvinyl chloride, polycarbonate, a polyamide (e.g. Nylon, etc.), polyurethane, an aromatic polyether ketone resin, a polyphenylene sulfide, acrylonitrile butadiene styrene (ABS); styrene acrylonitrile copolymers (SAN); poly (vinylcyclohexane); PMMA/poly (vinylfluoride) blends; poly (phenylene oxide) alloys; styrenic block copolymers; polyimide; polysulfone; poly (vinyl chloride); poly (dimethyl siloxane) (PDMS); polyurethanes; unsaturated polyesters; poly (alkane terephthalates), such as poly(ethylene terephthalate) (PET); poly (alkane naphthalates), such as poly(ethylene naphthalate) (PEN); ionomers; vinyl acetate/polyethylene copolymers; cellulose acetate; cellulose acetate butyrate; fluoropolymers; poly (styrene)-poly (ethylene) copolymers; poly (carbonate)/aliphatic PET blends and PET and PEN copolymers, including polyolefinic PET and PEN, including any copolymer and any mixture thereof.

In some embodiments, the synthetic biodegradable polymer is or comprises anyone of: Polyglycolic acid, Polyorthoester, Polyphosphoester, Polyanhydride, Polyester-amide, Polyaminoacid (e.g. random polyaminoacid), polyimine, Poly (L-lactic acid), Poly (caprolactone), Poly (lactic-coglycolic acid), Poly (3-hydroxybutyric acid), Poly (sebacic acid), Poly (adipic acid), Polyposphazene, Poly (dioxanone), Poly-β-hydroxybutyrate-co-β-hydroxy valerate (PHBV), and PBAT, including any copolymer and any mixture thereof.

In some embodiments, the additional polymer comprises a polymer derived from a natural product. In some embodiments, the additional polymer comprises a biodegradable polymer derived from a natural product. In some embodiments, the additional polymer comprises cellulose, silk, keratin and collagen, or any mixture or copolymer thereof. The composite material can be utilized in the production of paper or skin care and hair care products in order for the paper or skin care and hair care products to have improved characteristics, e.g. improved tensile strength or tear strength.

The Article

According to some embodiments, the present invention provides an article comprising a fiber as described herein (including inter alia coated fibers). In some embodiments, the article comprises a fiber comprising a lamin-based protein, wherein the fiber is characterized by a diameter between 10 μm and 180 μm. In some embodiments, the lamin-based protein comprises an A-type lamin, a B-type lamin or both, as described hereinabove.

In some embodiments, the article is in a form of a yarn comprising a plurality of fibers of the invention. In some embodiments, the article is in a form of a woven or a non-woven substrate. In some embodiments, the article is in a form of a filament, a film, a foam, a thread, a sphere, a particle, a microcapsule, a hydrogel, or a nanofibril. In some embodiments, the fiber of the present invention can be used or incorporated in any article for which desired characteristics are e.g. high toughness and stiffness.

Non-limiting examples of the article include the form of a suture, surgical mesh, medical adhesive strips, mesh, skin grafts, fat grafts, cosmetics, dermal fillers replacement ligaments, drug eluting/delivery device clothing fabric, bullet-proof vest lining, cable, tube, film, rope, fishing line, tire, glove, catheter, hose, shoe sole, sports equipment and a reinforced composite.

Mechanical Properties

In some embodiments, the disclosed article is characterized by an improved mechanical property as compared to a reference article. In some embodiments, the term “reference article” refers to a same article, being free of a fiber as disclosed herein. In some embodiments, the term “reference article” refers to a self-assembled fiber. In some embodiments, the term “reference article” refers to a fiber processed from an aqueous coagulation bath. In some embodiments, the term “reference article” refers to a uncoated fiber (i.e. the lamin-based protein fiber) of the invention.

By “improved mechanical property” it is meant to refer to having a more desirable mechanical property.

In some embodiments, the improved mechanical property refers to an elastic modulus. In some embodiments, the phrase “elastic modulus” refers to Young's modulus. In some embodiments, the phrase “elastic modulus” is determined by response of a material to application of tensile stress (e.g., according to procedures known in the art).

In some embodiments, the improved mechanical property refers to Flexural modulus. As used herein and in the art, the flexural modulus (also referred to as “bending modulus”) is the ratio of stress to strain in flexural deformation, or the tendency for a material to bend. Flexural modulus may be determined from the slope of a stress-strain curve.

In some embodiments, the property is selected from, without being limited thereto, Young's modulus, tensile strength, fracture strain, yield point, toughness, abrasion resistance, stiffness, creep resistance, work-to-failure, stress and percentage of elongation. In some embodiments, tests such as abrasion tests may also be performed in accordance with DIN.

Stiffness refers to the slope of the linear portion of a load-deformation curve. Work to failure refers to the area under the load-deformation curve before failure. Each of these can be measured and calculated by methods standard known in the art. In some embodiments, the term “stiffness” and the term “Young's modulus” are used herein interchangeably.

In some embodiments, the tensile strength of a material refers the maximum amount of tensile stress that it can take before failure, for example breaking.

In some embodiments, the term “tensile strength” as used herein is the maximum amount of force as measured e.g., in Newton's that a material can bear without or prior to tearing, breaking, necking forming microcracks or fractures.

By “tearing, breaking, necking forming microcracks or fractures” it is meant to refer to a permanent deformation. In some embodiments, the term “permanent deformation” does not include microcracks or fractures. In some embodiments, by “permanent deformation” it is meant to refer to relative to at least 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 1% of the original dimension or structure, including any value therebetween.

In some embodiments, the term “fracture strain” means the strain (displacement) at fracture, as determined e.g., by the stress-strain curve in a tensile test.

In some embodiments, the term “yield point” refers to the stress at which the stress-strain curve has a plateau and the elastic limit is reached.

As used herein, “creep” is a measure of the change in tensile strain when a polymer sample is subjected to a constant tensile stress, for instance, gravity or applied mechanical or physical stress. Put differently, creep is the tendency of a solid material to slowly move or deform permanently under the influence of a constant tensile stress. As used herein, the term “creep resistance” refers to a polymer's ability to resist any kind of distortion when under a load over an extended period of time. “Improved creep resistance” may refer to improvement by e.g., 20 percent of the time to e.g., 5% tensile strain.

In some embodiments, the term “stress at elongation” refers to the force that acts on the material in the stretched condition. For example, “stress at 100% elongation” refers to the force that acts on the material stretched to twice its length.

In some embodiments, one or more properties selected from Young's modulus, tensile strength, yield point, and stress at elongation, is enhanced by e.g., at least 1%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 50%, at least 100%, at least 200%, or at least 500%.

In some embodiments, one or more properties selected from Young's modulus, tensile strength, yield point, and stress at elongation, is enhanced by e.g., at least 100%, at least 150%, at least 250%, at least 250%, at least 260%, at least 270%, at least 280%, at least 290%, at least 300%, at least 350%, at least 400%, at least 450%, at least 500%, at least 550%, at least 600%, at least 650%, at least 700%, at least 750%, at least 800%, at least 850%, at least 900%, at least 1000%, at least 1500%, at least 2000%, at least 2500%, or at least 3000%.

In some embodiments, at least two properties selected from Young's modulus, tensile strength, yield point, and stress at elongation, is enhanced by e.g., at least 1%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 50%, at least 100%, at least 200%, or at least 500%.

In some embodiments, at least three properties selected from Young's modulus, tensile strength, yield point, and stress at elongation, are enhanced by e.g., at least 1%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 50%, at least 100%, at least 200%, or at least 500%.

In some embodiments, the Young's modulus is enhanced by e.g., at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 50%, at least 100%, at least 200%, or at least 500%.

In some embodiments, the tensile strength is enhanced by e.g., at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, or at least 50%.

In some embodiments, the yield point is enhanced by e.g., at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, or at least 50%.

In some embodiments, the article is characterized by a structural strength, wherein more than 20% of the structural strength results from the incorporated fiber(s). In some embodiments, the composition is characterized by a structural strength, wherein more than 20% of the structural strength results from the incorporated fiber(s). In some embodiments, the composite is characterized by a structural strength, wherein more than 30% of the structural strength results from the incorporated fiber(s).

In some embodiments, the article is characterized by a structural strength, wherein more than 1%, more than 5%, more than 10%, more than 20%, or more than 30% of the structural strength results from the incorporated fiber(s). In some embodiments, the composition is characterized by a structural strength, wherein more than 1%, more than 5%, more than 10%, more than 20%, or more than 30% of the structural strength results from the incorporated fiber(s).

In some embodiments, the phrase “structural strength”, as used herein, refers to the mechanical properties such as, without being limited thereto, elastic modulus, tensile stress, elongation (strain) and toughness [e.g., combination of tensile stress and elongation (strain)].

The Method

According to an aspect of some embodiments of the present invention there is provided a method for obtaining a fiber as described hereinabove. In some embodiments, the method comprises the steps of: a. providing a lamin-based protein at a concentration between 10 mg/mL and 400 mg/mL; and b. contacting (or injecting) the lamin-based protein with a coagulation solution, thereby forming the fiber. In some embodiments, contacting comprises injecting.

In some embodiments, providing a lamin-based protein is at a concentration between 10 mg/mL and 400 mg/mL, between 20 mg/mL and 400 mg/mL, between 30 mg/mL and 400 mg/mL, between 50 mg/mL and 400 mg/mL, between 70 mg/mL and 400 mg/mL, between 100 mg/mL and 400 mg/mL, between 200 mg/mL and 400 mg/mL, between 10 mg/mL and 250 mg/mL, between 20 mg/mL and 250 mg/mL, between 30 mg/mL and 250 mg/mL, between 50 mg/mL and 250 mg/mL, between 70 mg/mL and 250 mg/mL, or between 100 mg/mL and 250 mg/mL, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the coagulation solution is characterized by a viscosity between 0.45 cP and 3 cP, between 0.46 cP and 3 cP, between 0.47 cP and 3 cP, between 0.48 cP and 3 cP, between 0.5 cP and 3 cP, between 0.45 cP and 2.5 cP, between 0.46 cP and 2.5 cP, between 0.47 cP and 2.5 cP, between 0.48 cP and 2.5 cP, between 0.5 cP and 2.5 cP, between 0.45 cP and 2 cP, between 0.46 cP and 2 cP, between 0.47 cP and 2 cP, between 0.48 cP and 2 cP, between 0.5 cP and 2 cP, between 0.45 cP and 1 cP, between 0.46 cP and 1 cP, between 0.47 cP and 1 cP, between 0.48 cP and 1 cP, or between 0.5 cP and 3 cP, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the coagulation solution is characterized by a viscosity of more than 0.7 cP, more than 0.8 cP, more than 0.9 cP, more than 1 cP, more than 1.5 cP, more than 1.7 cP, or more than 2 cP, including any value therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the injecting is at a flow rate of at least 0.1 ml/h, at least 0.2 ml/h, at least 0.5 ml/h, at least 0.7 ml/h, at least 1 ml/h, at least 1.7 ml/h, at least 2 ml/h, at least 5 ml/h, at least 10 ml/h, at least 15 ml/h, or at least 20 ml/h, including any value therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the injecting is through a needle with an inner diameter between 0.001 mm and 1 mm, between 0.005 mm and 1 mm, between 0.01 mm and 1 mm, between 0.02 mm and 1 mm, between 0.001 mm and 0.9 mm, between 0.005 mm and 0.9 mm, between 0.01 mm and 0.9 mm, between 0.02 mm and 0.9 mm, between 0.001 mm and 0.5 mm, between 0.05 mm and 0.5 mm, between 0.09 mm and 0.5 mm, between 0.1 mm and 0.5 mm, between 0.12 mm and 0.5 mm, between 0.13 mm and 0.5 mm, between 0.15 mm and 0.5 mm, between 0.05 mm and 0.3 mm, between 0.09 mm and 0.3 mm, between 0.1 mm and 0.5 mm, between 0.12 mm and 0.3 mm, between 0.13 mm and 0.3 mm, between 0.15 mm and 0.3 mm, between 0.05 mm and 0.2 mm, between 0.09 mm and 0.2 mm, between 0.1 mm and 0.2 mm, between 0.12 mm and 0.2 mm, between 0.13 mm and 0.2 mm, or between 0.15 mm and 0.2 mm, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the coagulation solution comprises (i) an alcohol (ii) an aqueous solution (ii) a buffer solution, or any combination thereof.

In some embodiments, the alcohol is selected from methanol (MeOH), ethanol (EtOH), propanol (PrOH), isopropyl alcohol (IPA), butanol, pentanol, including any additional water miscible alcohol (e.g. C1-C5 alcohol, or C1-C3 alcohol) or any combination thereof.

In some embodiments, the coagulation solution comprises between 50% (v/v) and 100% (v/v), between 60% (v/v) and 100% (v/v), between 65% (v/v) and 100% (v/v), between 69% (v/v) and 100% (v/v), between 70% (v/v) and 100% (v/v), between 72% (v/v) and 100% (v/v), between 75% (v/v) and 100% (v/v), between 50% (v/v) and 99% (v/v), between 60% (v/v) and 99% (v/v), between 65% (v/v) and 99% (v/v), between 69% (v/v) and 99% (v/v), between 70% (v/v) and 99% (v/v), between 72% (v/v) and 99% (v/v), between 75% (v/v) and 99% (v/v), between 50% (v/v) and 98% (v/v), between 60% (v/v) and 98% (v/v), between 65% (v/v) and 98% (v/v), between 69% (v/v) and 98% (v/v), between 70% (v/v) and 98% (v/v), between 72% (v/v) and 98% (v/v), between 75% (v/v) and 98% (v/v), between 50% (v/v) and 90% (v/v), between 60% (v/v) and 90% (v/v), between 65% (v/v) and 90% (v/v), between 69% (v/v) and 90% (v/v), between 70% (v/v) and 90% (v/v), between 72% (v/v) and 90% (v/v), or between 75% (v/v) and 90% (v/v), of the alcohol, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the aqueous solution comprises a cross-linker. In some embodiments, the cross-liker comprises any of: a divalent metal ion (e.g. Ca²⁺) or a salt thereof (such as CaCl₂) and MgCl₂), a covalent cross-linker (such as glutaraldehyde, paraformaldehyde), or any combination thereof.

In some embodiments, the aqueous solution comprises between 1 mM and 100 mM, between 2 mM and 100 mM, between 3 mM and 100 mM, between 4 mM and 100 mM, between 5 mM and 100 mM, between 10 mM and 100 mM, between 30 mM and 100 mM, between 50 mM and 100 mM, between 1 mM and 90 mM, between 2 mM and 90 mM, between 3 mM and 90 mM, between 4 mM and 90 mM, between 5 mM and 90 mM, between 10 mM and 90 mM, between 30 mM and 90 mM, between 50 mM and 90 mM, between 1 mM and 70 mM, between 2 mM and 70 mM, between 3 mM and 70 mM, between 4 mM and 70 mM, between 5 mM and 70 mM, between 10 mM and 70 mM, between 30 mM and 70 mM, or between 50 mM and 70 mM of a crosslinker, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the aqueous solution comprises between 1 mM and 100 mM, between 2 mM and 100 mM, between 3 mM and 100 mM, between 4 mM and 100 mM, between 5 mM and 100 mM, between 10 mM and 100 mM, between 30 mM and 100 mM, between 50 mM and 100 mM, between 1 mM and 90 mM, between 2 mM and 90 mM, between 3 mM and 90 mM, between 4 mM and 90 mM, between 5 mM and 90 mM, between 10 mM and 90 mM, between 30 mM and 90 mM, between 50 mM and 90 mM, between 1 mM and 70 mM, between 2 mM and 70 mM, between 3 mM and 70 mM, between 4 mM and 70 mM, between 5 mM and 70 mM, between 10 mM and 70 mM, between 30 mM and 70 mM, or between 50 mM and 70 mM of a divalent metal ion salt, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the aqueous solution comprises between 1 mM and 100 mM, between 2 mM and 100 mM, between 3 mM and 100 mM, between 4 mM and 100 mM, between 5 mM and 100 mM, between 10 mM and 100 mM, between 30 mM and 100 mM, between 50 mM and 100 mM, between 1 mM and 90 mM, between 2 mM and 90 mM, between 3 mM and 90 mM, between 4 mM and 90 mM, between 5 mM and 90 mM, between 10 mM and 90 mM, between 30 mM and 90 mM, between 50 mM and 90 mM, between 1 mM and 70 mM, between 2 mM and 70 mM, between 3 mM and 70 mM, between 4 mM and 70 mM, between 5 mM and 70 mM, between 10 mM and 70 mM, between 30 mM and 70 mM, or between 50 mM and 70 mM of CaCl₂, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the aqueous solution comprises between 0.1% (v/v) and 10% (v/v), between 0.2% (v/v) and 10% (v/v), between 0.5% (v/v) and 10% (v/v), between 0.9% (v/v) and 10% (v/v), between 1% (v/v) and 10% (v/v), between 3% (v/v) and 10% (v/v), between 5% (v/v) and 10% (v/v), between 0.1% (v/v) and 7% (v/v), between 0.2% (v/v) and 7% (v/v), between 0.5% (v/v) and 7% (v/v), between 0.9% (v/v) and 7% (v/v), between 1% (v/v) and 7% (v/v), between 3% (v/v) and 7% (v/v), between 5% (v/v) and 7% (v/v), of a cross-linker, including any range therebetween. Each possibility represents a separate embodiment of the invention.

In some embodiments, the method comprises at least one step of (i) drying the fiber, and (ii) stretching the fiber. In some embodiments, the step of (i) drying the fiber, is performed after step b.

In some embodiments, the method further comprises a step (c) contacting the fiber with a hydrophobic agent, thereby forming a coating layer on the fiber. In some embodiments, the step of (i) drying the fiber, is performed after step c.

In some embodiments, a fiber obtained by the method as described hereinabove is devoid of microfibers.

In some embodiments, the method further comprises a step (iii) preceding the step a., of purifying the lamin-based protein.

In some embodiments, step (iii) of purifying the lamin-based protein comprises: (a) solubilizing the lamin-based protein in a chaotropic agent; (b) removing the chaotropic agent; and (c) contacting the lamin-based protein with a metal ion. In some embodiments, step (b) and step (c) comprise dialysis. In some embodiments, step (b) and step (c) comprise two independent dialysis.

General

As used herein the term “about” refers to +10% or +20%. Further, the entire numerical values disclosed herein are approximations also encompassing variations of +10% or +20% from the disclosed values. It is to be understood, that all numerical values disclosed herein are preceded by the term “about”.

The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”.

The term “consisting of means “including and limited to”.

The term “consisting essentially of” means that the composition, method or article (e.g. fiber of the invention, or an article processed therefrom) may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or article. Further, the term “consisting essentially of” is used to define articles or compositions which include the recited elements but exclude other elements that may have an essential significance on the article or on the composition.

The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict.

As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

Materials and Methods

In this study, the inventors explored the potential of Ce-lamin fibers, by employing wet spinning approach to spin Ce-lamins into fibers. In comparison with a self-assembly approach, wet spinning allows the preparation of thinner fibers with better control over the fiber diameter. The inventors hypothesized that proteins with different domain architectures would assemble into different networks of paracrystals, each with unique mechanical properties, when prepared under different conditions. For this purpose, the inventors used three protein constructs with the following composition of domains: the coiled-coil rod domain (rod-Ce-lamin, 40 kDa, SEQ ID NO: 11), rod and tail domains (rod-tail-Ce-lamin, 59 kDa, SEQ ID NO: 12), and all three domains (full-length-Ce-lamin, 64 kDa, SEQ ID NO: 10) (FIG. 1A). Fibers from these constructs were prepared using different injection flow rates and Ca⁺²concentrations in the coagulation buffer and their mechanical properties were compared. The inventors also tested whether assembly condition affected the structure of the paracrystals (different organization of the protofilaments) or their organization into network.

Expression and Purification of C. elegans Lamins

The plasmid pET24d (Novagen) containing the 1 mn-1 (NC_003279.8) gene was constructed as per previously reported methods. The rod- and rod-tail-Ce-lamin genes were cloned with an N-terminal 6×His-TEV site and a C-terminal AVI-tag in pET24d (+) (Novagen) to generate 6His-TEV-Ce-laminAvi. The plasmids were transformed into Escherichia coli BL21 derivative Rosetta (DE3) plysS. An overnight bacterial culture was diluted (1100) into fresh LBmedium and grown to an OD600 of 0.5-0.9. IPTG (0.3 mM) was added and after 3 h, bacteria were harvested by centrifugation. The pellet containing inclusion bodies was re-suspended in a re-suspension buffer (20 mM Tris-HCl, pH 7.6, 200 mM NaCl, 1 mM EDTA) containing 1:10,000 v/v Calbiochem Protease Inhibitor Cocktail Set III and 1% v/v Tween 20. The bacterial suspension was sonicated for 10 min (3 s on and 4 s off) at 65% pulse (EXLAB model BM-150) and was centrifuged at 8000×g for 10 min at 4° C. Inclusion bodies were washed twice with the re-suspension buffer and then incubated with 20 unit/mL Benzonase Nuclease (Novagen, Denmark) for 30 min. Next, inclusion bodies were centrifuged again at 8000×g for 10 min at 4° C. and then dissolved in urea buffer (20 mM Tris-HCl, pH 7.6, 50 mM NaCl, and 6 M Urea). Finally, the suspension was centrifuged at 17,000×g for 1 h at 4° C. The supernatant was then concentrated to the desired concentration by centrifugal concentrators (30,000-kDa cutoff). Nanodrop was used to prepare the desired concentration (100 mg/mL) and ratio (260/280, ˜1.1) of Ce-lamin solutions.

Assembly of C. elegans Lamins into Fibers

Purified Ce-lamins (full-length, rod-tail, and rod) in 6 M urea containing buffer (100 mg/mL) were dialyzed (11,000 v/v) against the dope solution conditions (0.5 M urea, 100 mM NaCl, 25 mM Tris-HCl, pH=9, and 1 mM dithiothreitol (DTT)). After dialysis, lamin solutions were centrifuged for 1 h at 17,000×g to remove aggregates, and they were then injected, at room temperature, via syringe pump (Chemyx NanoJet syringe pump) at injection flow rates of 0.5, 1.0, and 3.5 mL/h through a syringe needle (22S ga, model 710 Hamilton@ syringe) into coagulation baths until fibers were formed. The coagulation bath contained 25 mM Tris-HCl, pH 9.0, 20 or 50 mM CaCl₂, and 1 mM DTT. Finally, the fibers were stored at room temperature in coagulation buffers containing ˜20% 2-propanol until tensile testing. All wet fibers used in the study were stable in the tubes for at least two years.

Hydrophobic Coating of Fibers

Fibers from the coagulation solution were initially air-dried for 20 minutes. The dry fibers were immersed in the desired coating oil for times range from 15 min to 24 h, and then were air-dried for 20 minutes. The dry fibers were immersed then into a water tank for 24 h. After that, the fibers were air-dried for 20 min, after which they underwent tensile tests.

Scanning Electron Microscopy Imaging of Ce-Lamin Macrofibers

Scanning electron microscopy (SEM) imaging was carried out using the Thermo Verios 460 L (Thermo Fisher Scientific Inc.) instrument equipped with a field emission gun. Samples were coated with chromium prior to imaging. Secondary electron images were recorded at 3 keV and at a working distance of 8.1 mm.

Preparation of Ce-Lamin Macrofiber Sections for TEM Imaging

Fibers based on Ce-lamins were sequentially treated at room temperature with 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.35), post-fixed with 1%0.0 in 0.1 M cacodylate buffer, and block stained with 1% aqueous uranyl-acetate for 1 h each. Samples were then dehydrated in an ethanol series and embedded in Epon/Araldite (Sigma-Aldrich, Buchs, Switzerland). Ultrathin (70 nm) sections were post-stained with lead citrate and examined with the Tecnai G2 Spirit transmission electron microscope (Thermo Fisher Scientific, Eindhoven, The Netherlands) at an acceleration voltage of 120 kV and using the Orius 1000 digital camera (Gatan, Munich, Germany). The diameter range was measured using ImageJ from the TEM-section images (Table 4). Using the same tool, the repeat-length (dark/black and bright/white segment) along individual paracrystals was measured as the length between the two centers of the black regions and the average repeat length was calculated.

Characterization of Mechanical Properties of Ce-Lamin Fibers

Tensile testing of individual fibers was performed at room temperature using a single column universal testing machine (Shimadzu, AGS-x) with a 100 N load cell and at crosshead velocities of 0.3, 10, and 100 mm/min. During the uniaxial tensile test, environmental conditions, such as temperature (˜25° C.) and humidity (˜50%), were kept relatively fixed. Five to ten fibers were tested for each combination of conditions. Individual fiber (0.5 cm) was mounted onto a cardstock paper frame and glued at both ends.

Affixing the fibers with glue protects them from deformation during sample mounting on the apparatus, which must be done with extreme care. Fiber lengths were measured using a standard ruler. The wet spun fibers were air dried for 10 min before stretching. Full-length Ce-lamin fibers formed at injection rate of 3.5 mL/h into coagulation bath containing 20 mM CaCl₂were also air dried for 6 or 24 h. Force-displacement curves were converted to stress strain curves by dividing the force by the average cross-sectional area of the fiber (assuming a circular cross-section). Importantly, after testing, fiber diameters were measured at five different locations distributed evenly along the length of each fiber using a light microscope. The average diameter was then used to calculate fiber cross-sectional area. Breaking stress (i.e., strength) and breaking strain were therefore calculated as the engineering stress and strain (dL/L0), respectively, at failure. Young's modulus is the slope of the stress-strain curve at the elastic linear region of the curve prior to the yield point. Additionally, strain energy at failure (i.e., toughness) was calculated by measuring the area under the stress-strain curve.

Statistical Analysis

Multi-factorial ANOVA, according to t- and F-tests (p-value <0.05) were conducted using JMP v.13 to analyze the effects of protein type, CaCl₂) concentration in coagulation baths, injection flow rates and crosshead velocities on the mechanical properties of the fibers. The effects of the combined treatments (statistical interactions) were also analyzed.

Raman Analysis
Data Collection

The Raman system comprised a Horiba Lab Ram HR evolution micro-Raman system equipped with a Synapse Open Electrode CCD detector air-cooled to −60° C. The excitation source was a 785 nm diode laser with a power of 50 mW on the sample. The laser was focused to a spot measuring about 2 μm by using a ×50 objective. The measurements were taken with a 600 g mm-1 grating and a 100 μm confocal microscope hole. Exposure time was 900 s.

Data Treatment

To quantify the obtained results as precisely as possible, the inventors validated them by using estimation procedure that is based on Monte-Carlo simulation and model estimation. This method models the data as a Gaussian Mixture Model (GMM), that is, a probability density function (pdf) comprising a fixed number of K weighted normal pdfs with different means and variances. In that framework, the pdf estimation is defined as:

$\begin{matrix} f = \sum_{k = 1}^{K} α_{k} N (μ_{k}, σ_{k}) & (1) \end{matrix}$

where N (μn, σn) is a normal pdf with mean un and standard deviation σn, and α1, α2, . . . , αK are weights such that α1+α2+ . . . +αK=1. A well-known algorithm for the joint estimation of the parameters (μn,σn,αn), n=1 . . . . K, is the expectation maximization (EM) algorithm, whose convergence to a local maximum of the likelihood function of the parameters is guaranteed. Thus, it can be decomposed as follows: after normalization of the spectrum to an integral 1 (to render it indeed a pdf), the inventors generated 106 samples of this distribution with an accept reject procedure, and based on this sample and on the assumption that the number of Gaussian K=5, the inventors estimated f with the EM algorithm. Since convergence when using this method is guaranteed to a local maximum only, initialization was an important part of the procedure. The inventors initialized the weights and variances with uniform values (αn=0.2, σn=20 for all n=1 . . . . K). Furthermore, the averages, un, were initialized based on the values found in the literature. Note that in that approach, the estimation of all the parameters in Eq. (1) was performed jointly, and therefore, in principle, the parameters' values must be interpreted jointly. However, the inventors observed that in practice, the estimated variances and means barely differ from their values at initialization. Therefore, the practical interpretation can be performed based only on the values of an.

Example 1

Recombinant expression of Ce-lamins (FIG. 1A) in E. coli as inclusion bodies usually involves their solubilization in the presence of a high concentration of a chaotropic agent, such as urea, at the end of purification process (FIG. 1B). Thus, in vitro formation of the paracrystals requires the removal of urea and subsequent addition of Ca⁺²ions in two consecutive dialysis steps. In order to avoid the formation of aggregates at the first step, the assembly of paracrystals was carried out only at low concentration of lamins (0.1-1 mg/mL). However, in order to spin fibers in the wet spinning approach, high solution viscosity is required, which can be achieved by using high protein concentration. Therefore, the dope solution composition (0.5 M urea, 100 mM NaCl, 25 mM Tris-HCl, pH 9, and 1 mM DTT) was first optimized to ensure that Ce-lamins remain soluble at a concentration of 100 mg/mL. The dope solutions were injected at rate of 0.5, 1, or 3.5 mL/h into the coagulation bath containing 20 mMor 50 mM CaCl₂) (Tables 1, 2, and 3).

TABLE 1

Mechanical properties of rod Ce-lamin fibers formed at injection rate

of 0.5, 1, and 3.5 mL/h into a coagulation bath containing 20 mM or 50

mM CaCl₂, and strained at rates of 0.3, 10, and 100 mm/min.

Rod Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

0.3
10
100
0.3
10
100
0.3
10
100

mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/

min
min
min
min
min
min
min
min
min

20 mM CaCl₂

Diameter
61 ±
49 ±
50 ±
29 ±
51 ±
60 ±
58 ±
40 ±
40 ±

(μm)
5
4
5
4
9
3
10
3
2

Young's
1.9 ±
2.6 ±
3.4 ±
1.3 ±
3.4 ±
2.2 ±
2.2 ±
2.5 ±
4.7 ±

modulus
0.5
0.4
0.9
0.4
09.
0.3
0.7
0.4
0.7

(GPa)

Yield
34.4 ±
40.6 ±
61.2 ±
15.9 ±
51.6 ±
32.4 ±
18.7 ±
36.8 ±
63.1 ±

stress
13.4
8.6
26.2
68.
17.9
5.5
45.
13.6
54.

(MPa)

Break
63.0 ±
63.5 ±
73.3 ±
48.8 ±
66.2 ±
56.0 ±
55.5 ±
58.2 ±
76.4 ±

stress
19.4
19.5
19.1
16.3
14.7
5.4
16.7
15.6
11.6

(MPa)

Break
1.2 ±
1.4 ±
1.3 ±
1.2 ±
1.3 ±
1.4 ±
1.2 ±
1.4 ±
1.4 ±

strain
0.2
0.3
0.3
0.2
02.
0.1
0.1
0.2
0.2

(mm/mm)

Toughness
52.7 ±
48.9 ±
61.9 ±
26.6 ±
57.3 ±
48.6 ±
36.0 ±
42.8 ±
66.4 ±

(MJ/m³)
23.6
20.6
21.4
11.4
18.4
8.2
96.
15.2
841.

50 mM CaCl₂

Diameter
49 ±
42 ±
46 ±
29 ±
45 ±
46 ±
61 ±
44 ±
42 ±

(μm)
5
2
7
3
6
3
12
2
6

Young's
2.5 ±
4.9 ±
3.7 ±
1.5 ±
3.7 ±
4.1 ±
1.8 ±
1.6 ±
4.5 ±

modulus
0.6
0.8
0.9
0.5
0.7
0.6
0.4
0.3
1.1

(GPa)

Yield
25.1 ±
79.6 ±
69.1 ±
17.6 ±
58.3 ±
81.4 ±
17.3 ±
23.5 ±
51.4 ±

stress
58.
12.7
15.7
90.9
18.8
14.7
51.
71.
67.

(MPa)

Break
40.6 ±
95.3 ±
81.5 ±
26.2 ±
73.2 ±
86.3 ±
54.7 ±
49.7 ±
78.5 ±

stress
13.2
10.9
20.7
16.5
16.8
17.1
21.8
46.
14.2

(MPa)

Break
1.1 ±
1.4 ±
1.3 ±
0.9 ±
1.2 ±
1.2 ±
1.3 ±
1.3 ±
1.5 ±

strain
0.1
0.1
0.2
0.1
0.1
0.2
0.2
0.1
0.1

(mm/mm)

Toughness
26.4 ±
91.0 ±
67.6 ±
13.4 ±
54.3 ±
71.9 ±
31.6 ±
32.0 ±
61.3 ±

(MJ/m³)
77.
6.6
12.0
81.
13.1
20.0
14.3
52.
13.2

TABLE 2

Mechanical properties of rod-tail Ce-lamin fibers formed at injection rate

of 0.5, 1, and 3.5 mL/h into a coagulation bath containing 20 mM or 50

mM CaCl₂, and strained at rates of 0.3, 10, and 100 mm/min.

Rod-tail Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

0.3
10
100
0.3
10
100
0.3
10
100

mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/

min
min
min
min
min
min
min
min
min

20 mM CaCl₂

Diameter
41 ±
32 ±
27 ±
57 ±
38 ±
44 ±
41 ±
42 ±
40 ±

(μm)
4
7
2
8
6
2
4
6
2

Young's
1.8 ±
3.5 ±
9.2 ±
1.2 ±
2.0 ±
3.6 ±
1.8 ±
2.4 ±
4.4 ±

modulus
0.2
14.
2.0
0.5
06.
02.
0.1
0.7
0.4

(GPa)

Yield
16.6 ±
59.6 ±
111 ±
12.3 ±
28.4 ±
44.1 ±
13.7 ±
34.4 ±
50.1 ±

stress
40.
18.9
20
70.
8.5
7.6
47.
10.0
85.

(MPa)

Break
39.3 ±
89.7 ±
118 ±
31.8 ±
35.5 ±
54.8 ±
25.9 ±
49.4 ±
58.0 ±

stress
18.6
27.6
33
33.
12.2
8.7
69.
21.0
15.9

(MPa)

Break
1.3 ±
1.3 ±
1.4 ±
1.3 ±
1.3 ±
1.4 ±
1.1 ±
1.4 ±
1.4 ±

strain
0.3
02.
0.2
0.1
02.
01.
0.3
0.2
0.2

(mm/mm)

Toughness
24.5 ±
71.7 ±
107 ±
16.9 ±
24.6 ±
54.2 ±
16.8 ±
46.8 ±
59.0 ±

(MJ/m³)
10.8
22.3
38
34.
6.5
12.5
96.
16.2
17.2

50 mM CaCl₂

Diameter
35 ±
35 ±
40 ±
39 ±
46 ±
40 ±
51 ±
45 ±
45 ±

(μm)
3
6
3
8
3
5
6
3
4

Young's
1.2 ±
2.5 ±
4.1 ±
2.4 ±
2.2 ±
4.9 ±
2.0 ±
2.5 ±
3.9 ±

modulus
0.3
08.
0.2
0.7
03.
08.
0.8
0.3
0.5

(GPa)

Yield
15.1 ±
37.1 ±
53.7 ±
17.7 ±
32.1 ±
54.6 ±
20.2 ±
38.2 ±
49.8 ±

stress
58.
12.0
12.4
47.
3.8
8.3
10.9
12.6
95.

(MPa)

Break
56.5 ±
67.4 ±
59.6 ±
60.1 ±
44.2 ±
66.4 ±
47.6 ±
46.6 ±
67.7 ±

stress
16.5
15.6
13.5
29.1
12.2
11.1
23.6
83.
16.3

(MPa)

Break
1.4 ±
1.5 ±
1.5 ±
1.3 ±
1.2 ±
1.5 ±
1.2 ±
1.4 ±
1.5 ±

strain
0.2
02.
0.3
0.3
02.
03.
0.2
0.1
0.2

(mm/mm)

Toughness
42.5 ±
50.1 ±
59.7 ±
38.1 ±
36.6 ±
56.4 ±
29.0 ±
44.2 ±
70.7 ±

(MJ/m³)
10.8
15.8
17.6
24.7
7.0
14.1
12.6
88.
11.7

TABLE 3

Mechanical properties of full-length Ce-lamin fibers formed at injection rate

of 0.5, 1, and 3.5 mL/h into a coagulation bath containing 20 mM or 50

mM CaCl₂, and strained at rates of 0.3, 10, and 100 mm/min.

Full-length Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

0.3
10
100
0.3
10
100
0.3
10
100

mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/
mm/

min
min
min
min
min
min
min
min
min

20 mM CaCl₂

Diameter
49 ±
38 ±
37 ±
32 ±
35 ±
46 ±
33 ±
32 ±
35 ±

(μm)
9
5
4
7
8
10
3
2
3

Young's
1.8 ±
2.4 ±
5.3 ±
1.9 ±
2.3 ±
3.7 ±
5.5 ±
8.4 ±
7.2 ±

modulus
0.6
0.8
1.2
0.7
1.2
1.6
0.6
1.5
1.5

(GPa)

Yield
17.4 ±
30.7 ±
51.5 ±
16.7 ±
31.2 ±
41.3 ±
60.7 ±
129.3 ±
145.6 ±

stress
7.1
13.2
11.8
6.3
15.5
15.8
12.6
25.6
35.6

(MPa)

Break
40.5 ±
39.3 ±
50.2 ±
62.2 ±
54.4 ±
45.4 ±
120.2 ±
128.7 ±
119.4 ±

stress
19.4
12.5
26.6
8.4
24.1
16.6
36.1
20.8
28.2

(MPa)

Break
1.3 ±
1.2 ±
1.4 ±
1.3 ±
1.2 ±
1.2 ±
1.5 ±
1.6 ±
1.3 ±

strain
0.3
0.2
0.2
0.1
0.1
0.0
0.3
0.3
0.4

(mm/mm)

Toughness
42.7 ±
27.4 ±
47.5 ±
49.0 ±
35.1 ±
36.6 ±
135.2 ±
149.8 ±
143.1 ±

(MJ/m³)
30.6
7.5
23.8
7.4
16.1
14.7
44.4
39.6
45.0

50 mM CaCl₂

Diameter
49 ±
54 ±
46 ±
51 ±
57 ±
45 ±
49 ±
49 ±
51 ±

(μm)
9
11
8
9
13
7
8
7
4

Young's
1.6 ±
1.7 ±
3.7 ±
1.6 ±
1.6 ±
3.7 ±
1.5 ±
4.0 ±
3.2 ±

modulus
0.7
0.8
1.4
0.5
0.5
1.2
0.9
1.0
0.3

(GPa)

Yield
17.6 ±
22.6 ±
51.5 ±
15.6 ±
22.1 ±
63.7 ±
26.3 ±
55.3 ±
59.2 ±

stress
8.3
11.6
16.3
6.6
9.2
29.1
9.1
18.8
7.9

(MPa)

Break
63.3 ±
50.5 ±
71.9 ±
40.3 ±
30.5 ±
72.8 ±
82.6 ±
64.6 ±
69.6 ±

stress
18.0
24.1
26.8
8.9
7.3
28.0
26.2
25.9
19.2

(MPa)

Break
1.3 ±
1.5 ±
1.7 ±
1.3 ±
1.1 ±
1.0 ±
1.7 ±
1.4 ±
1.6 ±

strain
0.2
0.1
0.2
0.3
0.1
0.2
0.2
0.3
0.2

(mm/mm)

Toughness
48.0 ±
38.2 ±
82.4 ±
31.4 ±
22.2 ±
57.3 ±
89.2 ±
69.4 ±
93.9 ±

(MJ/m³)
15.6
19.5
35.6
11.2
4.7
22.3
29.6
31.4
36.1

The wet spinning approach, rather than dialysis-based self-assembly approach, allowed the inventors to obtain wet fibers with smaller and more uniform diameter (˜170 μm). The inventors did not detect microfibers within fibers, as seen with the dialysis procedure. To confirm the formation of paracrystals in the coagulation buffers the inventors analyzed the structure of Ce-lamin wet fibers using TEM imaging, which revealed 70-nm thick cross sections. In this technique, the internal structure of wet macroscopic fibers can be visualized at the nanometric level. Despite the high Ce-lamin concentration, most Ce-lamin fibers comprised massive network of paracrystals (FIGS. 2A-C), in which the diameters ranged between 30 nm and 150 nm (FIGS. 2B-C and Table 4).

TABLE 4

Diameter range of the paracrystals within Ce-lamin fibers

formed at injection rate of 0.5, 1, and 3.5 mL/h into a coagulation

bath containing 20 mM or 50 mM CaCl₂.

Rod Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

20 mM CaCl₂

Diameter
10-15
10-15
10-20

(nm)

50 mM CaCl₂

Diameter
10-25
10-50
20-40

(nm)

Rod-tail Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

20 mM CaCl₂

Diameter
30-200
40-50
10-30

(nm)

50 mM CaCl₂

Diameter
30-100
15-40
70-250

(nm)

Full-length Ce-lamin

0.5 mL/h
1 mL/h
3.5 mL/h

20 mM CaCl₂

Diameter
30-100
30-130
20-120

(nm)

50 mM CaCl₂

Diameter
50-250
50-250
30-100

(nm)

Before mounting the fibers onto the tensile test machine, the wet fibers were air dried for 10 min, which caused the fiber diameter to shrink to 50-80 μm. EM images (FIGS. 1C-H) showed some microfibers formation after drying. Thus, drying probably caused the paracrystal networks to undergo structural re-organization due to the evaporation of water; however, the inventors assume that the structure of individual paracrystal remained unchanged in the presence of moisture. Increasing the drying time above 10 min did not cause further shrinkage of the fibers, and had no significant impact on the mechanical properties after 6 or 24 h (Table 5).

TABLE 5

The effect of drying time on the diameter and mechanical properties of

full-length Ce-lamin fibers formed at injection rate 3.5 mL/h into a

coagulation bath containing 20 mM CaCl₂(optimal assembly conditions).

Full-length Ce-lamin

20 mM CaCl₂, 3.5 mL/h, 10 mm/min

Drying time
10 min
6 h
24 h

Diameter (μm)
32 ± 2
31 ± 3
30 ± 4

Young's modulus
8.4 ± 1.5
8.5 ± 1.8
8.7 ± 2.1

(GPa)

Yield stress (MPa)
129.3 ± 25.6
124.8 ± 17.5
137.4 ± 29.6

Break stress (MPa)
128.7 ± 20.8
125.2 ± 29.1
135.4 ± 24.2

Break strain
1.6 ± 0.3
1.5 ± 0.3
1.4 ± 0.2

(mm/mm)

Toughness (MJ/m³)
149.8 ± 39.6
145.2 ± 34.2
141.1 ± 36.0

All dry fibers were mechanically strained at rates of 0.3, 10, and 100 mm/min by using a single column universal testing machine. The response of all Ce-lamin fibers to tensile force was similar to those of other IF-protein-based fibers, for instance, hydrated hard α-keratins, vimentin and the lamin fibers that were assembled through dialysis procedure. Specifically, a linear elastic region (1.4%-5%) was seen up to the yield point, after which the long plastic region was obtained until the fiber failure (FIG. 3). Furthermore, due to the experimental setup, Ce-lamin fibers exhibited wide range of mechanical properties (Tables 1, 2, and 3), which were not influenced (p value >0.05) by injection flow rate, CaCl₂) concentration, or protein structure alone, but by their synergistic effect (significant statistical interactions, p-value <0.05) (Table 4). Indeed, for each protein construct, the inventors found a combination of conditions (injection flow rate and CaCl₂) concentration) that resulted in optimal mechanical performances (FIG. 3). These specific conditions will be referred from now on as optimal assembly conditions. In comparison with regenerated and recombinant hagfish slime, vimentin, and self-assembled Ce-lamin protein-based fibers, wet spun Ce-lamin fibers showed better stiffness and toughness, which were comparable to natural dragline silk and natural hagfish slime threads.

To study the effect of different combinations of assembly conditions on the mechanical performance, the inventors examined how assembly conditions influenced on the paracrystal structure. Namely, the width of the paracrystals or the mode of protofilaments association within paracrystals could be a factor in the fiber mechanics. First, the inventors measured the paracrystal width, which was in the range of 10-50 nm for rod, 10-250 nm for rod-tail, and 20-250 nm for full-length Ce-lamins (Table 4). The width of paracrystals in the fibers formed at the optimal assembly conditions (FIG. 3), for each protein construct, showed no significant difference from the other assembly conditions. Thus, the different paracrystal widths did not influence the fiber mechanics. Second, the black-white average repeat lengths along individual paracrystal were measured. The average repeated lengths indicate the mode of dimers and protofilaments association within individual paracrystals. The average repeat lengths in full-length and rod-tail-Ce-lamin fibers were ˜40 nm (FIGS. 2A-C and FIGS. 5A-C) for all assembly conditions, which suggested that the protofilament association did not exert influence under the different spinning conditions. Moreover, under most conditions rod-Ce-lamins formed filamentous network that lacked the repeat length. These networks were similar in morphology and filament diameter to the paracrystals analyzed at higher resolution using cryoelectron tomography reported in the literature. In that study, it was suggested that the protofilament association into paracrystals was similar to those of the full-length-Ce-lamin, and the lack of average repeat-length was probably due to the removal of the long and dense tail domain (179 amino acids), particularly its Ig-fold segment. Therefore, the inventors assumed that the filamentous structures of the rod-Ce-lamin fibers were thin paracrystals. Thus, the inventors could not determine if the different assembly conditions had any effect on the protofilaments organization into rod-Ce-lamin fibers.

The inventors also tested whether the diameter of dry fibers after tensile test could be correlated with the mechanical properties for each Ce-lamin construct (FIGS. 4A-C). The continuous tension on the fibers during the tensile test at different crosshead velocity caused further shrinkage of the diameter of the dry fibers (50-80 μm) to 27-61 μm (FIG. 4D). Fibers with the smallest diameter could exhibit the highest stiffness and toughness characteristics. At the optimal assembly conditions, (FIG. 3) rod-Ce-lamin fibers showed an average diameter similar to the fibers formed in other conditions. In contrast, the diameters of rod-tail and full-length Ce-lamin fibers form were smaller than the fibers formed in other conditions; however, these differences were not statistically significant (FIGS. 4A-C). For example, the full-length Ce-lamin fibers, formed in coagulation bath containing 20 mM CaCl2 at injection rate of 1 or 3.5 mL/h and then strained at 0.3 mm/min, displayed similar diameters on an average, but displayed completely different stress, stiffness, and toughness. Moreover, full-length Ce-lamin fibers that assembled in the dialysis procedure were, after tensile test, much thicker (˜217 μm) compared to the wet-spun fibers (˜50 μm) (this study). Both fibers were strained at crosshead velocity of 0.3 mm/min, and showed similar average stress, stiffness, and toughness. This probably meant that on one hand the fiber diameter did not influence the fiber mechanics, but on the other hand, it implied that if the inventors could make thinner fibers using the dialysis procedure, the fibers would be tougher and stiffer. Lastly, a close look on the morphology of the full-length Ce-lamin fibers (FIGS. 1F-H) showed more uniform structure, which was comprised of compacted micron size (1-2 μm) microfibers, than in rod and rod tail fibers that were comprised of non-uniformed thicker microfibers. These differences in organization and in the size of the microfibers may account for the difference in mechanical properties between the fibers at the optimal conditions.

To assess whether the amount of β-sheet structures formed due to secondary structure transition upon stretching of the wet-spun Ce lamin fibers could be a factor in fibers mechanics, the inventors applied Raman spectroscopy (FIGS. 5A-C). The secondary structure transition from α-helix to β-sheet, that yielded a stiffer and stronger fiber than the elastic α-helices-rich fiber, constitutes a major contributor to the high strength and strain of spider silk and α-keratin fibers. The Raman spectra (FIGS. 5A-C) of the toughest fibers (FIG. 3), before and after the mechanical test, showed typical peaks in the amide I band region corresponding to the α-helix (1650 cm⁻¹) and the β-sheet and/or to the random coil structures (1667 cm⁻¹) (FIGS. 5A-C). To evaluate the increase in numbers of β-sheet structures as a result of the pulling process, the inventors used independent curve fitting method that models the curve as a mixture of four Gaussians whose parameters are estimated by using the regular EM algorithm. The results showed that the β-sheets increased in number and the α-helix structures decreased in number. The rod-based fiber showed a milder increase (4%) in β-sheet structures than was found in the rod-tail (12%) and full-length (8%) Ce-lamins. Despite these differences, the inventors did not find any effect of the increase in β-sheet structures on the stiffness, breaking stress, and strain percentage of the fibers formed at the optimal conditions. This result, however, may suggest that the presence of C-terminal sequence, N-terminal sequence, or both sequences promote the formation of β-sheet structures during the tensile test by forming tightly packed protofilaments. Thus, the inventors speculate that the fiber stress-strain properties were not affected by higher β-sheet structures formation, fiber diameter, paracrystals width, or protofilament association (average repeat length), but by the number of connection points between paracrystals, which could be perceived as the number of interactions between protofilaments from two separated paracrystals. Therefore, the structural rearrangements during the tensile test may begin with unraveling of those interconnected paracrystals caused by the alignment and sliding of the protofilaments that connect them. This may lead to breakage of the Ca⁺²intermolecular crosslink, thereby causing irreversible deformation of the connection points between paracrystals leading to the yield point. From this point, the alignment and sliding of the protofilaments and polymers of dimers within paracrystals continues until the fiber breaks (FIGS. 6A-B). According to this, based on the Ce-lamin constructs studied here, the effect of the addition of C terminus or both N- and C-termini to the rod domain on the mechanical properties was not evident. However, at the optimal conditions, the full length fiber showed the highest stiffness and toughness at all crosshead velocities. Furthermore, rod and rod-tail fibers showed similar stiffness and toughness at crosshead velocity of 0.3 mm/min, whereas at 10 mm/min both fibers showed better stiffness and toughness, with rod fibers demonstrating better properties. Further increasing the velocity to 100 mm/min led to very high stiffness and toughness of the rod-tail fibers as opposed to rod fibers that exhibited decrease in properties. At most assembly conditions, increasing velocity led to higher stiffness, except at the optimal condition of rod and full-length fibers. In these cases, the stiffness decreased at 100 mm/min, whereas for the rod-tail fibers, the stiffness increased 2.5 fold. This probably stems from the effect of the N- and C-termini, at specific conditions, on the binding of coiled coil domains in the dimer formation and on the association of two dimers, thus, strengthening the dimers and protofilaments.

This study demonstrates that a recombinant IF-protein, Ce-lamin, can be solubilized and wet-spun into aqueous solutions to form wet macroscopic fibers (diameter ˜ 170 μm) composed of a complex network of paracrystals (diameter range of 10-250 nm) as revealed by TEM-sections analysis. Our results suggested that the mechanical properties depended probably on the formation of specific network of paracrystals formed under specific assembly conditions. To investigate the paracrystals networks further, higher resolution structural analysis would be necessary to reveal the protofilaments mode of association between two interconnected paracrystals at different assembly conditions. Raman analysis demonstrated an increase in β-sheet structures. Potentially, Ce-lamin coiled-coils can transform completely into β-sheet structures, thus enabling them to withstand a higher strain percentage and to achieve a higher breaking stress. Nevertheless, the high toughness of Ce-lamins fibers is attributed mainly to their large strain percentage, which might arise from the fast reorganization and relaxation of the paracrystals, protofilaments and rod domain, when subjected to stress. Therefore, the formation of thinner fibers in which local defect are less prone to cause fiber breakage may approach theoretically complete transformation.

Ce-lamin dry fibers were characterized by a combination of high breaking strain, moderate-to-high stiffness and strength that rendered them as tough as native hagfish threads and spider silk fibers. Among the soft biomaterial-based proteins, lamin fibers exhibit unique mechanical properties; they strain to a much higher percentage than silk, keratin, or collagen and have a similar stiffness, but they break at lower stress. Ce-lamin can thus be exploited as components in composite biomaterials in diverse applications that are suitable for highly tough and stiff fibers. The possibility of lamins of different types from different organisms exhibiting a wide range of mechanical properties is intriguing. For example, the mode of association involved in the assembly of human lamin A dimers into paracrystal is different from that of Ce-lamin. The altered paracrystal structure may affect the mechanics of the fibers. Other prospects would be to analyze composite fiber comprising two types of lamins, such as human lamins A and B1, as found at the periphery of the cell nucleus.

Example 2
Ce-Lamin-Based Fiber Fabrication in Alcoholic Solutions

The wet spinning method is based on the extrusion process in which a polymer solution is injected into a coagulation bath to form fibers. The properties and structure of the fibers will be affected by, among other things, the injection speed, the diameter of the syringe needle, the composition of the coagulation bath, and the concentration of the protein in the dope solution. Here, the effect of the coagulation bath composition on Ce-lamin fibers was examined, while the rest of the parameters remained constant. That is, Ce-lamin protein solutions at a concentration of 100 mg/mL were injected at a flow rate of 1.5 mL/h through a 0.168 mm inner diameter needle into different coagulation solutions. The inventors successfully utilized various alcohol-based solutions (e.g. MeOH, EtOH, PrOH, IPA) at concentrations between 50% and 100%, for the formation of fibers.

The strain-stress curves of all fibers obtained after tensile test, at a rate of 10 mm/min, showed similar nonlinear mechanical behavior to viscoelastic materials and other intermediate filaments proteins based fibers that is a short elastic region of 3-6% and long plastic deformation. Some of the fibers tested showed higher toughness and strain values than Ce-lamin fibers injected into aqueous solvents. The mean strain values of these fibers approached a 200%.

RAMAN Spectroscopy Analysis

RAMAN spectroscopy was performed to examine the secondary structure of the proteins within fibers, e.g. the ratio of α-helix to β-sheet and the change of this ratio at different tensile stages. Information on the region/stage in which the major transition between α-helix and β-sheet occurs can shed light on understanding which properties of the alcohol and the coagulation bath affect the mechanical properties of the fibers. In this analysis, fibers injected into 70% ethanol were tested at various stages shown in FIG. 7A. In each test, intensity curves were obtained against a wave number (FIG. 8). The area under each curve describes the relative amount of the secondary structures, and by statistical calculations new curves can be constructed one of which describes the total amount of α-helix and the other the total amount of β-sheet. As shown in FIG. 7A, the transition from α-helix to β-sheet occurs mostly in the elastic phase, since up to a strain of 6% (right after the yield point (˜5%)) a decrease in the amount of α-helix and an increase in the amount of β-sheet can be seen. After a strain of 6% there is no significant change in the percentages of the two different structures.

The Raman analysis was done on different fibers for each strain percentage and demonstrated that transition propagation was different for fibers assembled in 70% ethanol (7A) and an aqueous buffer containing 20 mM CaCl₂(7B). The relative amount of α-helix to β-sheet structures was similar at 0% strain and failure in both conditions. However, a significant part of the α-β transition in fibers assembled in 70% ethanol occurred up to a strain of 6%, with little change until failure. In contrast, in fibers made in the aqueous buffer, the relative amount of α-helices to β-sheets stayed relatively constant until 20% strain (see FIG. 7B).

Furthermore, the inventors subjected fibers obtained from an alcoholic solution and from calcium chloride solution to cyclic strain tests. Surprisingly, two significant differences between the assembly conditions were observed:

- 1. Fibers assembled in 70% ethanol showed prominent hysteresis in the five cycles test (FIG. 12B), whereas CaCl₂coagulated fibers exhibited an almost linear elastic behavior, as reflected by almost identical strain/stress curves (FIG. 12A)
- 2. Raman spectroscopy analysis (FIGS. 12C-D) shows that when the five cycles test ends at an extended position (FIG. 12C), there are more α-helices; namely, there was no transition in the secondary structure during the cycle test. In contrast, fibers assembled in 70% ethanol, the cycle test ended at a relaxed position (FIG. 12D) and showed more of the β-sheets/random coil structures. Thus, during the five-cycle test, a non-reversible transition to β-sheets/random coil from α-helices occurred in the fibers obtained via alcoholic coagulation.

Scanning Electron Microscope (SEM) Analysis

Using SEM analysis, the inventors have examined the surface morphology of dry Ce-lamin fibers that were assembled in 50% and 70% ethanol and IPA. FIGS. 9A-D and FIGS. 10A-C illustrate the surface of fibers that either did not or did experience tensile load, respectively. All the fibers before stretching were comprised of a large cluster of nanometer fibers that constitute the structural units of the macroscopic fibers. Only in IPA the nanofibers associate into microfibers that together make up the macroscopic fibers. After stretching, the microscopic fibers organization in the IPA-fibers disappear. Measuring the diameter of the nanofibers showed that in 50% alcohol the diameter of the fibers was lower than in 70%, in both ethanol and IPA (Table 6). The difference in diameters was on average 16 nm in ethanol and 13 nm in IPA. Before stretching, the surface morphology of the dry Ce-lamin fibers comprised a large cluster of nano-filaments that constitute the macroscopic fibers' structural units. The diameter of the nano-filaments assembled in 50% alcohol was lower at ˜15 nm than either 70% ethanol or IPA. These differences might explain the lower mechanical strength of the fibers formed in 50% alcohols.

TABLE 6

The diameter of the nano-fibers at each condition.

Ethanol
IPA

50%
46.45 ± 7.32 nm
48.87 ± 1.08 nm

70%
56.47 ± 3.58 nm
62.07 ± 0.09 nm

TABLE 7

Stress-strain properties of the Ce-lamin fibers assembled in various alcoholic solutions

Young's
Yield
Yield
Break

Alcohol
Alcohol
Thickness
Modulus
Stress
Strain
Stress

Type
%
(μm)
(GPa)
(MPa)
(mm/mm)
(MPa)

Methanol
50
51 ± 9
2.75 ± 1.18
64.19 ± 34.20
0.04 ± 0.01
65.73 ± 30.93

70
49 ± 18
3.32 ± 1.46
71.24 ± 26.59
0.04 ± 0.01
70.86 ± 33.47

100
55 ± 13
2.71 ± 1.07
53.66 ± 26.21
0.03 ± 0.00
52.46 ± 24.61

Ethanol
50
43 ± 7
3.78 ± 0.64
85.68 ± 8.56
0.04 ± 0.01
90.10 ± 10.42

70
30 ± 10
4.78 ± 1.38
157.41 ± 50.41
0.06 ± 0.02
168.09 ± 50.47

100
43 ± 5
2.96 ± 0.32
78.13 ± 21.56
0.04 ± 0.01
102.38 ± 32.54

IPA
50
41 ± 9
3.83 ± 0.53
67.11 ± 15.58
0.03 ± 0.01
73.24 ± 18.70

70
33 ± 6
4.51 ± 1.42
132.39 ± 34.87
0.06 ± 0.02
145.86 ± 31.44

100
32 ± 2
1.17 ± 0.39
31.39 ± 8.41
0.06 ± 0.02
49.08 ± 15.49

Break

Alcohol
Alcohol
Strain
Toughness

Type
%
(mm/mm)
(MJ/m³)

Methanol
50
1.13 ± 0.31
61.31 ± 37.06

70
1.06 ± 0.27
61.49 ± 30.92

100
1.39 ± 0.09
53.52 ± 31.38

Ethanol
50
1.27 ± 0.23
93.72 ± 17.57

70
1.89 ± 0.62
258.77 ± 134.49

100
1.97 ± 0.57
132.14 ± 70.18

IPA
50
1.39 ± 0.36
79.81 ± 44.49

70
1.78 ± 0.55
190.68 ± 73.39

100
1.87 ± 0.29
63.59 ± 23.29

Films

The inventors further successfully formed transparent films (e.g. hydrogel films) composed of the full-length lamin-based protein fibers of the invention (data not shown). Both fiber obtained from an aqueous and alcoholic coagulation have been successfully implemented for the film formation, using a dialysis procedure in 70% ethanol, or in in an aqueous buffer containing 20 mM CaCl₂), respectively. The resulting films exhibited the desired mechanical strength (e.g. strain at break of about 300%. Furthermore, Q159K mutated in Ce-lamin fiber have been implemented for the formation of transparent films. Mechanical properties of the films are summarized in Tables 7A-B below.

TABLE 7A

The stress-strain properties of the Ce-lamins-

based dry films assembled in 70% ethanol.

Young's
Yield
Yield
Break
Break

modulus
stress
strain
stress
strain
Toughness

(Mpa)
(Mpa)
(mm/mm)
(Mpa)
(mm/mm)
(MJ/m³)

Full-
916 ± 30
15.5 ± 2
0.031 ± 0.01
21.68 ± 5
1.16 ± 0.3
20.2 ± 3

length

Q159K
940 ± 43
53 ± 10
0.055 ± 0.02
46 ± 6
0.36 ± 0.05
17 ± 2

Rod
660 ± 35
25.6 ± 4
0.065 ± 0.02
18.8 ± 3
0.88 ± 0.1
16 ± 3

TABLE 7B

The stress-strain properties of the Ce-lamins-based dry films

assembled in an aqueous buffer containing 20 mM CaCl₂

Young's
Yield
Yield
Break
Break

modulus
stress
strain
stress
strain
Toughness

(Mpa)
(Mpa)
(mm/mm)
(Mpa)
(mm/mm)
(MJ/m³)

Full-
253 ± 30
11 ± 2
0.12 ± 0.03
16.5 ± 3
3 ± 0.3
30 ± 4

length

Q159K
885 ± 40
23.1 ± 4
0.06 ± 0.01
17.5 ± 3
1.33 ± 0.3
24 ± 5

Furthermore, the inventors currently performing various experiments in order to test the compatibility of the fibers of the invention with additional polymeric matrices, so as to obtain reinforced composite materials. The inventors will test various additional synthetic and/or natural and/or biodegradable polymers (such as disclosed hereinabove) to manufacture composites with different constant of the fibers of the invention (such as disclosed herein). The composites can be prepared by casting, melting, extrusion, dipping, spreading, coating, or any other method known in the field of polymer processing.

To this end, the inventors successfully formed an epoxy-resin based composite, demonstrating excellent compatibility of the fibers of the invention at least with synthetic resins (e.g. thermoset resins). Thus, it is postulated that additional polymers will be compatible with the fibers of the invention, allowing formation of composites with varying content of the fibers of the invention.

Hydrophobic Coating to Ce-Lamin Fibers

In nature, the protein core of silk and hair fibers is coated with a hydrophobic layer. Though this layer do not contribute directly to the fiber mechanical properties, it protects the protein fibers from hydration and external damages. Fibers can be coated with lubricants or finishes, such as polymers or wax finishes including but not limited to mineral oil, fatty acids, isobutyl-stearate, tallow fatty acid 2-ethylhexyl ester, polyol carboxylic acid ester, coconut oil fatty acid ester of glycerol, alkoxylated glycerol, a silicone, dimethyl polysiloxane, a polyalkylene glycol, polyethylene oxide, and a propylene oxide copolymer. The inventors coated the fibers that were assembled in 70% ethanol with paraffin oil at different immersion times to check their effect on fiber mechanics. For the overnight (O.N) immersion time, the coated Ce-lamin fibers were much stronger and strained to higher percentage (Table 8), thus reaching to very high toughness (˜600 MJ/m³), and further exhibiting a significantly increased strain at failure of about 400% and even more, compared to uncoated fibers.

TABLE 8

Stress-strain properties of the Ce-lamin fibers assembled

in 70% ethanol and later coated with paraffin oil.

Immersion

Young
Yield
Yield
Break
Break

time of in
Diameter
Modulus
stress
strain
stress
strain
Toughness

paraffin oil
(mm)
(MPa)
(MPa)
(mm/mm)
(MPa)
(mm/mm)
(MJ/m³)

15 min-
43.8
3771.0
124.2
0.0480
144.6
1.1
129.5

Avg

60 min-
40.0
4327.0
113.2
0.0350
204.0
2.1
286.0

Avg

O.N-Avg
36.7
8871.0
235.8
0.0434
311.5
3.0
622.5

15 min-
1.5
1330.0
38.0
0.0200
35.8
0.5
73.3

STD

60 min-
3.0
1059.0
19.4
0.0230
82.0
0.05
24.3

STD

O.N -STD
15.5
6364.3
160.7
0.0198
154.8
0.4045
377.0

Furthermore, the inventors tested swelling behavior of the coated versus un-coated fibers. Coated with paraffin oil (A) or non-coated (B), Ce-lamin fibers were soaked in water for four days. The fibers' swelling was observed only in non-coated fibers demonstrating the water-repellent (or even superhydrophobic) effect of the hydrophobic coating.

The inventors subjected the coated fibers to cyclic strain tests. 5 cycles experiments demonstrated linear elastic behavior of the coated fibers. Raman spectroscopy analysis shows that when the five cycles test ends at an extended position, the fibers have more beta-sheets/random coil and fewer alpha-helices compared to the relaxed position, which has more α-helices. Thus, during the five-cycle test, a reversible transition to beta-sheets/random coil from α-helices occurred.

Example 3
Human Lamin A-Based Fibers

The native environment of lamins within the cell nucleus force the A- and B-type lamins filaments, each of which form a distinct fiber meshwork, to form biocomposite material with nuclear membranes, lamin associated proteins, and chromatin, which undoubtedly affect their structure and mechanics. Here the inventors expressed type A of human lamin (corresponding to amino acid sequence SEQ ID NO: 9) and wet-spun them into three different coagulation baths: 1. 70% ethanol in water, 2. Tris-buffer (20 mM Tris-pH-9, 20 mM CaCl₂)). 3. MES-buffer (50 mM MES-pH-6, 10 mM CaCl₂)). Bacterial expression, protein purification, dope solution preparation were performed as described in Ce-lamins procedures.

Overall, human lamin A-based fibers had the same stress-strain behavior as the Ce-lamin fibers, but were less tough and strong (Table 8A).

TABLE 8A

Stress-strain properties of the human lamin A-based fibers

assembled in 70% ethanol, and TRIS and MES buffers.

Young
Yield
Yield
Break
Break

Modulus
stress
strain
stress
strain
Toughness

(MPa)
(MPa)
(mm/mm)
(MPa)
(mm/mm)
(MJ/m³)

70% ethanol-Avg
2595.3
46.6
0.0301
34.3
0.9
27.0

Tris-20 mM Ca⁺²-
2562.9
47.7
0.0329
42.1
1.2
55.6

Avg

MES-20 mM Ca⁺²-
3616.8
75.9
0.0322
86.0
1.5
91.3

Avg

70% ethanol-STD
969.4
15.5
0.0010
4.3
0.5
9.9

Tris-20 mM Ca⁺²-
307.0
4.6
0.0024
2.3
0.1
24.9

STD

MES-20 mM Ca⁺²-
754.6
24.4
0.0035
27.2
0.1
23.4

STD

Example 4
Mutated Ce-Lamin Based Fibers

The Q159K mutation in Ce-lamin is analogous to the E145K mutation in Lamin A in humans which is one of the causes of progeria disease. The amino acid glutamine is replaced by lysine at position 159. The mutant protein solutions were injected into coagulation baths containing 70% ethanol and 70% IPA. The mutation significantly affected the yield and breaking stresses, breaking strain, and toughness, did not change much the Young's modulus and the fiber diameter (FIG. 11 and Table 9). The average toughness of the native fibers was 3 times greater than that of mutated fibers in ethanol, and more than two times in IPA. Although the mutant lamin protein-based fiber has been characterized by reduced toughness, the fibers are suitable for industrial applications, especially such application which do not require excessive mechanical strength.

Furthermore, it is postulated that the physical properties (e.g. mechanical strength and/or Young's modulus) of various mutants might be modulated to result fibers with tailored physical properties. Such fibers may be useful in various composite materials, where similar physical properties (e.g. Young's modulus) of the constituents are required.

TABLE 9

Comparison between the stress-strain properties of the Ce-lamin

and Q159K-Ce-lamin fibers assembled in alcoholic solutions.

Young's
Yield
Yield
Break
Break

Alcohol
Alcohol
Thickness
Modulus
Stress
Strain
Stress
Strain
Toughness

Type
%
(μm)
(GPa)
(MPa)
(mm/mm)
(MPa)
(mm/mm)
(MJ/m³)

w.t

Ethanol
70
30 ±
4.78 ±
157.41 ±
0.06 ±
168.09 ±
1.89 ±
258.77 ±

10
1.38
50.41
0.02
50.47
0.62
134.49

IPA
70
33 ±
4.51 ±
132.39 ±
0.06 ±
145.86 ±
1.78 ±
190.68 ±

6
1.42
34.87
0.02
31.44
0.55
73.39

Q159K

Ethanol
70
36.33 ±
3.92 ±
75.65 ±
0.03 ±
76.38 ±
1.42 ±
83.54 ±

10.00
0.95
16.98
0.00
27.96
0.29
36.35

IPA
70
35.89 ±
4.79 ±
80.92 ±
0.03 ±
87.46 ±
1.47 ±
82.35 ±

5.67
1.60
32.46
0.00
31.21
0.34
41.26

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

WET-SPUN LAMIN-BASED FIBERS

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