Patent Application
20090198184
The present technology relates to implantable percutaneous biomedical devices having a biocompatible implantable interface region and methods of implanting percutaneous biomedical devices to prevent infection and inflammation of the implant-skin interface.
The statements in this section merely provide background information related to the present technology and may not constitute prior art. In the past decade, there have been numerous advances in the development of transcutaneous devices including nails, fixator pins, screws, catheters, glucose sensors, prostheses and osteointegrative prosthetic limb devices for amputees to name but a few. The skin of a patient who wears a transcutaneous device is subject to numerous abuses.
Typically, the implantable percutaneous biomedical devices are made of stainless steel, titanium or polymeric materials. The soft tissue area in contact with the implantable device is the one that most likely will present an inflammatory response, in particular, in the dermal and epidermal layers of the skin. In addition, the interface remains “unsealed” enabling the seeding of microbial based infections. The state of the skin is of utmost importance, for example, to an amputees' ability to use a prosthesis particularly an osseointegrated prosthesis limb device. If the normal skin condition cannot be maintained despite daily wear and tear, the prosthesis cannot be worn, no matter how accurate the integrated limb device may be.
Poor hygiene may be an important factor in producing some pathologic conditions of the transcutaneous-skin interface. If a routine cleansing program is not employed, bacterial and fungal infections, nonspecific eczematization, intertrigo, and persistence of infected epidermoid cysts can eventuate.
Bacterial folliculitis and furuncles or boils are often encountered in amputees with hairy, oily skin, with the condition aggravated by sweating and rub from the transcutaneous device. It is usually worse in the late spring and summer when increased warmth and moisture from perspiration promote maceration of the skin in contact with the transcutaneous device. Ordinarily this process is not serious, but sometimes, especially in diabetics, it can progress to furuncles, cellulitis, or an eczematous weeping, crusted, superficial, impetiginized pyoderma. In some patients, therapy may require a wet compress, incision and drainage of the infectious interface after localization and oral or parenteral use of antibiotics, and local application of bacteriostatic or bactericidal agents.
In order to reduce or possibly eliminate the foreign-body-like reaction and microbial infection, the present technology provides for a biocompatible material at the skin-device interface that works as a tissue-integrative device.
Several fully internal osseointegrated devices have been described for orthopedic applications. In some cases, titanium joint arthroplasties incorporating osseointegration principles have been implemented and have gained usage worldwide. Notwithstanding the mechanical advantages of these transcutaneous devices however, concerns have been raised regarding their transcutaneous effects. The concerns are not about the integration of the device with bone but about the development of pathways around the implant through soft tissues, where environmental contamination have caused titanium corrosion and bone infection. Corrosion and infection could lead to further loss of bone length, resulting in a shorter residual limb and decreased function. Infection, bone loss, and loosening are common in transcutaneous implants.
Many responses to the problems associated with transcutaneous devices have focused on eliminating contact between the bone and the environment and restricting contamination of the prosthesis and bone. To this effect, the field has generally adopted strategies that encourage dermal and epithelial growth into prosthetic surfaces. However, problems associated with such biointegration stem from the fact that the transcutaneous devices may not remain completely stationary, i.e. these devices are dynamic, they can move under physical stresses imposed externally or internally. As a general principle, the human body reacts to insoluble foreign bodies placed within it either by extruding them (if they can be moved and an external wall is close at hand) or by walling them off by exactly the same process as wound granuloma formation. In other cases the local host response to an implant in contact with epithelial tissue will be the formation of a pocket or pouch continuous with the adjacent epithelial membrane, a process called “marsupialization” due to the structural similarity to a kangaroo's pouch. In the case of the external epithelium i.e. skin, marsupialization results in the extrusion of the implant from the host unless the implant is anchored in the deep connective tissue or other deep tissue.
The present technology provides for implantable devices that can remain partially implanted transcutaneously for an extended period of time without the deleterious effects described above.
The present technology relates to highly biocompatible percutaneous biomedical devices that can be partially implanted percutaneously into a patient. In particular, the present technology provides a body having a lumen extending longitudinally at least partially through the body, an implantable interface region disposed along the body. The implantable interface region has a plurality of radially extending conduits through the body, each of the conduits in fluid communication with the lumen and in fluid communication with an exit port. The implantable interface region is placed between the stratum corneum and the hypodermis layers of the subject's skin. The implantable interface region can include a plurality of radially extending conduits, each of the conduits is in fluid communication with a lumen and/or a reservoir and in fluid communication with an exit port to extrude a skin-interface composition between the subject's skin and the percutaneous biomedical device.
The lumen can store a skin-interface composition that is extruded at the skin-layer device interface. The radially extending conduits are each in fluid communication with the lumen and an exit port.
In another aspect the implantable interface region includes a first diameter and a second diameter, said second diameter being smaller than said first diameter and said second diameter defining a circumferential depression with a plurality of exit ports.
In another aspect, the present technology provides for methods of implanting a transcutaneous device. The method includes the steps of: providing a percutaneous biomedical device having an implantable interface region and a lumen for receiving a fluid comprising a skin-interface composition. The implantable interface region includes a plurality of radially extending conduits, such that the conduits are in fluid communication with the lumen and each conduit is in fluid communication with an exit ports; implanting the percutaneous biomedical device across the skin and in communication with a tissue and aligning said plurality of exit ports adjacent to a skin layer. Once implanted, the percutaneous biomedical device can form a skin layer interface by extruding a biocompatible, protective and nutritive skin-interface composition through the exit ports to contact the one or more skin layers.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present technology.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present technology in any way.
The following description is merely exemplary in nature and is not intended to limit the present technology, application, or uses.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on”, “engaged To”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The present technology relates to percutaneous biomedical devices providing an enhanced biocompatible skin-device interface, herein referred to as a skin layer interpace. A percutaneous biomedical device comprising a body having a lumen extending longitudinally at least partially through the body, an implantable interface region disposed along the body, the implantable interface region having a plurality of radially extending conduits through the body, each of said conduits in fluid communication with the lumen and in fluid communication with an exit port. As used herein, the implantable interface region can be constructed to serve as the percutaneous biomedical device or the implantable interface region can be integrated with or is part of a percutaneous biomedical device. The implantable interface region can be a part (or in its entirety) of any implant that is percutaneously implanted across a Subject's skin layer for an extended period of time. As used herein, a percutaneous biomedical device contemplates all transcutaneous devices that are implanted into a subject for a period of time longer than 2 weeks and in which a portion of the transcutaneous device extends through the skin and exits to the outside of the subject. The percutaneous biomedical device can include orthopedic devices including: fixator pins, orthopedic or craniofacial pins, rods, screws; prosthetic limb frames; prosthetic osseointegrated devices; catheters; stents; leads; wires and flexible or inflexible tubular devices that remain partially inserted in a subject for an extended period of time, typically greater than 2-3 weeks.
The percutaneous biomedical device can optionally also include a reservoir, a pumping mechanism to pump the contents of the reservoir into the lumen or exit ports of the implantable interface region and a skin-interface composition. The optional components, including the reservoir and pumping mechanism can be placed within the percutaneous biomedical device or placed outside of the percutaneous biomedical device. Additionally, the reservoir and pumping mechanism can be coupled to the implantable interface region or percutaneous biomedical device though connectors, which enable the reservoir and pumping mechanism to be placed outside of the subject's body.
The present technology provides a percutaneous biomedical device which allows the integration of the device with one or more layers of the skin. The percutaneous biomedical device can be any device that spans the epidermal, dermal and hypodermal skin layers of the subject. In some embodiments, the percutaneous biomedical device typically has an in vivo portion and an ex-vivo portion. The transcutaneous nature of the biomedical device is merely used to reference the in vivo portion of the transcutaneous being passed through the skin layers and placed within the body (in vivo). The portion of the percutaneous biomedical device that spans at least a portion of the epidermis and dermis layers can be referred to as the implantable interface region. Once the percutaneous biomedical device has been implanted, a skin-interface composition can be extruded from the implantable interface region's exit ports located between the stratum corneum of the epidermis and hypodermis layer of the subject's skin. The skin-interface composition is positively applied along at least a portion of the exterior surface of the implantable interface region in proximate contact with the one or more layers of the epidermal and dermal skin facilitating biological integration of the percutaneous biomedical device with the subject's skin. As used herein, the subject's skin comprises generally of three layers the epidermis layer, the dermis layer and the inner hypodermis layer that is composed largely of connective tissue. The movement of fluid from the hypodermis layer towards the epidermis is said to be superficial whereas, movement of fluid from the epidermis towards the hypodermis is said to be subcutaneously.
The implantable interface region 10 illustratively shown in
As illustrated in
The implantable interface region 10 further includes an ex vivo portion 14. Ex vivo portion 14 can be the portion of the transcutaneous device that is situated outside (exterior to) the subject's skin. In some embodiments, ex vivo portion 14 can be connected to a prosthesis. Ex vivo portion 14 can also refer to the proximal portion of the percutaneous biomedical device in reference to where the device is being manipulated by the operator. Implantable interface region 10 can be part of a larger or longer percutaneous biomedical device, for example a drug delivery tube, stent or catheter.
The percutaneous biomedical device has an implantable interface region 10, which at least partially spans the skin between the stratum corneum and the hypodermis. A first skin interface region 16 is illustrated in
As shown in
In some embodiments, best shown in
In some embodiments, the implantable interface region 10 can also include one or more circumferential depressions 50 wherein the exit ports 30 are circumferentially covered with a mesh material 40 to prevent entry of particles, debris, cells into the exit ports 30 and conduits 100. Mesh material 40 can be made from any biocompatible mesh material including metal, plastic or ceramic having a 5 μm to 50 μm mesh sieve opening size. The mesh material 40 can be made from metals or from one or more of Dacron®, polytetrafluorethylene, polypropylene, polyester, polyvinylidene fluoride (PVDF), silicone, Mersilene®, Marlex®, Nylon® and Teflon®.
The diameter of the implantable interface region 10 can vary according to several factors, including, the diameter of the percutaneous biomedical device, the material composition of the transcutaneous medical device and/or the implantable interface region 10, the function and purpose to be served by the percutaneous biomedical device and the subject's percutaneous biomedical device insertion site. For example,
The implantable interface region 10 can be manufactured from any biocompatible, non-toxic surgical grade plastics and metal materials including for example, ceramics, polymeric thermoplastics, silica containing synthetics, silicone containing synthetics and metals. It is preferred that the materials are surgical grade, biocompatible, non-immunogenic, non-toxic, sterilizable using chemical and/or physical sterilization (heat, ultraviolet and gamma radiation). Since these devices are to be implanted into a subject for an expended period of time, at least 2-3 weeks, the implantable interface region 10 is typically constructed from the same material used to fabricate the body of the percutaneous biomedical device. In some embodiments, the implantable interface region 10 is part of a percutaneous biomedical device including an orthopedic fixation system (for the fixation of skeletal and spinal bone structures) or an osseointegrating device, for which resiliency and load bearing capabilities are required to fixate an internal tissue such as bone or cartilage or for the support of a prosthetic device such as a prosthetic limb. In these examples, the implantable interface region 10 can be manufactured from one or more metals used for the manufacture of surgical implants, including orthopedic fixation, prosthesis frames, drug delivery needles, including surgical steel, titanium and their alloys, for example nitinol. The implantable percutaneous biomedical devices and the implantable interface region 10 can also have a coating, including a biocompatible material, such as a polymer like urethane, nylon, TPU, thermoplastic polyester elastomer, polyethyl, or silicone alone or in combination with one or more drugs, pharmaceuticals, biologics or medicaments. The coating can be applied to a percutaneous biomedical device by various methods, such as spray coating or painting.
The implantable interface region 10 also includes a lumen 20 as shown in
The lumen 20 can take the shape of a cylindrical void within the implantable interface region 10 as shown in
In some embodiments, the implantable interface region 10 can include a plurality of conduits 100. Conduits 100 are flow paths that are configured to channel the skin-interface composition from the internal reservoir 150 shown in
The conduits 100 can radiate from the central lumen 20 as shown in
The implantable interface region 10 includes two or more exit ports 30 placed circumferentially around the first skin interface region 16 or the one or more recessed skin interface surface 38 shown in
In an illustrative embodiment of the present technology, best illustrated in
In some embodiments, the implantable interface region 10 can have about at least four, or at least about eight, or at least about ten, or at least about 12, or at least about 16 exit ports disposed around the circumferential periphery of the implantable interface region.
While the skin-interface composition can be retained and provided in the lumen 20 for distribution along the conduits 100 and exiting through the exit ports 30, several embodiments can require the use of a reservoir to store an amount of skin-interface composition. To aid in the storage of the skin-interface composition, the implantable interface region 10 can be fluidly connected to one or more reservoirs. The reservoirs can be an internal reservoir 150 as exemplified in
In some embodiments, the function of the internal reservoir 150 is to temporarily store the skin-interface fluid for distribution to the conduits 100 for extrusion into the skin-device interface 250 as shown in
In some embodiments, the external reservoir 140 of the present technology can range from macro-sized reservoirs carrying capacities ranging from 1 mL to about 100 mL are widely known in the art. Micro-reservoirs that find utility in the present percutaneous biomedical devices can include microreservoirs fabricated using conventional photolithography and self-assembly and micro electromechanical systems where microreservoirs are etched onto silicate substrates. Other larger micro-macro sized reservoirs having deformable or semi-solid linings are well known in the art of stent and drug delivery systems. The reservoirs can be made of compliant synthetic or natural materials including elastomers, polymers and polysaccharide polymers, for example, ethylene vinyl acetate, Teflon, silicone, silastic and nylon, polyvinyl alcohol, ethylene vinyl acetate, polypropylene, polycarbonate, cellulose, cellulose acetate, cellulose esters or polyether sulfone.
In some embodiments, the reservoir supplying the skin-interface composition can be implanted in the subject's body and have connectors or other conduits to supply the implantable interface region 10 with the skin-interface composition. An illustrative example of an implantable system incorporating an external pump 160 is illustrated in
In some embodiments, the external reservoir 140 can be positioned externally to the subject and be connected to the percutaneous biomedical device 175 and implantable interface region 10 with percutaneous tubing or fluid lines. The use of external pumps has one advantage in that the reservoir can be kept completely sterile and can include large reservoirs that can be filled quickly. The external reservoir 140 can be attached to a delivery tube and a pump 160 for controlling delivery of the skin-interface composition through the delivery tube.
In some embodiments the percutaneous biomedical device 175 shown in
The types of pumps 160 for use to deliver the skin-interface composition from the external reservoir 140 can be any pump system used for sub-microliter to microliter volume delivery volumes. In some embodiments, the external reservoir 140 can include peristaltic pump, diaphragm pumps, piston pumps, gradients pumps, displacement pumps such as those described in (WO/2004/001228), isocratic pumps capable of pumping nanoliter to microliter scale volumes as described in U.S. Pat. No. 7,141,161 to Ito and any pumping system that is capable of providing flow rates of the skin-interface composition through the exit ports ranging from about 0.00015 μL per min to about 10 μL per min.
In some embodiments, the external reservoir 140 and internal reservoir 150 can also include micropumps and microfluidic type devices. Micro-pumps make it possible for nanoliter quantities of liquid to be dosed accurately and flexibly. Active composites and an electronic control mechanism ensure that the low-maintenance pump works accurately. Micropumps contemplated for the present pumping mechanism can include flexible peristaltic micropumps, diaphragm micropumps, thermopneumatic peristaltic micropumps and piezo electric driven micropumps which are all useful pumping mechanisms for the percutaneous biomedical devices described herein. Micropumps and microfluidic liquid delivery systems are commercially available from thinXXS Microtechnology AG Zweibrücken Germany. Other micropumps such as the Bartels microComponents' mp5 and mp6 micropumps (Mikrotechnik GmbH Dortmund, Germany).
In some embodiments, the pump 160 can be controlled wirelessly using wireless transmitter and receivers known in the fluid delivery art.
Referring to
In some embodiments, pump 160 can be coupled with intelligent delivery systems e.g. sensors illustrated in
The present percutaneous biomedical devices advantageously provide a skin-device interface 250 illustratively shown in
Other considerations in extruding a skin-interface composition from the implantable interface region and in preparing a skin-interface composition in accordance with the present technology includes preparing a composition having beneficial and regenerative activity for the epidermal cells and cells in the dermis and hypodermis. The skin-interface composition therefore includes one or more active agents that are known or believed to be beneficial to epidermal, dermal and hypodermal cells. The skin-interface composition of the present technology can also include one or more agents that are known or believed to be beneficial in the production of specific collagen species associated with healthy regenerating skin. In some embodiments, the skin-interface composition can include, as illustrative examples, one or more hydrophilic, biocompatible polymers for example, one or more polysaccharides, including glycosaminoglycans, for example dermatan sulfate, hyaluronic acid, the chondroitin sulfates, chitin, chitosan, alginate, heparin, keratan sulfate, keratosulfate, agarose, and derivatives thereof, carrageenan, guar gum, xanthan gums, locust bean gums, cellulose, polymers of cellulose, pectin and gellan. In some embodiments, the skin-interface composition can include collagen, fibronectin, laminin, and mixtures thereof. Synthetic polymers also useful in the composition can include: hydrophilic polymers including poly (vinyl alcohol), poly(ethylene glycol), poly(ethylene) oxide and mixtures thereof.
In some embodiments, the skin-interface composition can also include one or more bioactive agents including for example: natural and recombinant DNA, genes, cytokines, hormones, protein growth factors including for example: keratinocyte growth factor, epidermal growth factor, fibroblast growth factor and other known growth and differentiation factors implicated in skin regeneration and repair, pharmaceuticals, e.g., medicaments, anti-microbial agents, antibiotics, antiviral agents, microbistatic or virustatic agents, anti-inflammatory agents, such as dexamethasone and ibuprofen, anti-tumor agents, and immunomodulators; and metabolism-enhancing factors, e.g., amino acids, non-hormone peptides, ligands, vitamins, minerals, and natural extracts (e.g., botanical and marine animal extracts). The bioactive agent can also include processing, preserving, or hydration enhancing agents.
In some embodiments, a safe and effective amount of skin-interface composition is extruded from the implantable interface region 10 and coats the percutaneous biomedical device inserted through the skin along a partial length spanning a plurality of epidermal, dermal and hypodermal skin layers. The safe and effective amount of skin-interface composition creates a tissue-device interface that serves to lubricate the interface between the skin cells and the percutaneous biomedical device. Maintaining the lubricating interface also provides several advantages heretofore unexplored using such biomedical devices, for example: regeneration of skin cells along the tissue-device interface; assist in the production of healthy collagen proteins; reduce and/or prevent keratinocyte apoptosis; reduce and/or prevent infectious agents from entering into the tissue-device interfacial region and reduce and/or prevent fibrosis and scar formation at the tissue-device interface.
In some embodiments, the skin-interface composition can enhance the barrier role of such a composition placed at the tissue-skin interface by increasing the viscosity of the composition and thereby provide a cushioning effect between the device and the skin. In some embodiments, the skin-interface composition can be made to transition from a liquid to a gel by inducing a solidification transition by gellation, either by photoinitiation, exposure to water, or by native cationic or anionic species present in the tissue. The gel structure can also provide for a structural conduit for fibroblasts and other skin cells to form cellular skin networks, repopulate regions of the interface and provide a stable connection with the transcutaneous device to exclude foreign particles, microbes and other pathogenic conditions.
The skin-interface composition can be extruded from the exit ports 30 in a total amount ranging from about 1 to about 1000 μL per day, or from about 10 to about 1000, or from about 50 to about 1000 μL per day, or from about 100 to about 1000 μL per day, or from about 200 to about 1000 μL per day, or from about 1 to about 800 μL per day, or from about 1 to about 500 μL per day, or from about 1 to about 250 μL per day, or from about 1 to about 200 μL per day, or from about 1 to about 150 μL per day, or from about 1 to about 100 μL per day, or from about 1 to about 50 μL per day. In some embodiments, a safe and effective amount of skin-interface composition extruded from the exit ports 30 in total ranges from about 50 to about 500 μL per day.
The present technology presents several novel solutions for the incompatibility of using percutaneous biomedical devices for periods of time exceeding 2-3 weeks. The present technology provides a solution to the many problems associated in maintaining a healthy skin environment for the chronic use of percutaneous biomedical devices. The normal skin condition cannot be maintained despite daily wear and tear, the prosthesis cannot be worn, no matter how accurate the integrated limb device may be. In some embodiments, the percutaneous biomedical device of the present technology can include any known surgical, dental, and cosmetic device or appliance that is inserted through the skin of a patient and affixed to an internal tissue such that the device is operable having a portion of the device situated in the skin. It is to be understood that when one end of percutaneous biomedical device has been implanted into a tissue, a device-skin junction is formed. At present, several setbacks to the success of drug-delivery, orthopedic, prosthetic, and other surgical techniques have been identified at the transcutaneous site of implantation. The percutaneous biomedical device often fails because movement of the percutaneous biomedical device at the device-skin junction results in poor adhesion between the percutaneous biomedical device and the patient's skin layers. The loss of stability at the device-skin interface has often been associated with increased infections, skin fibrosis, and inflammatory reactions resulting in implant failure.
The present technology provides for methods for connecting a variety of percutaneous biomedical devices having an implantable interface region, for example, limb prosthetics, osseointegrated devices, catheters, stents, internal metabolic sensors, pace makers, defibrillators and orthopedic implants, including fixator pins, rods and screws across the skin in a manner that renders the device stable for an extended period of time and avoids issues associated with infection, persistent inflammation or rejection. In some embodiments, the partially implanted device member can be implanted in a patient for a period of at least about 2 weeks, at least about 7 weeks and at least about 14 weeks.
The skin-interface composition can be stored in a hollow cavity or reservoir disposed within the implantable interface region as shown in
The release of the skin-interface composition around the periphery of the implantable interface region is shown in
In some embodiments, the percutaneous biomedical device as illustratively shown in
Depending on the type of surgery undertaken and the duration the transcutaneous device must remain implanted, the surgeon or physician can monitor the physiological state of the implant, the degree of rejection and/or inflammation and/or the presence of infection at the skin-device interface and adjust the flow rate and composition of the skin-interface composition accordingly. For example, if the skin-interface composition at the skin-device interface fails to show infiltration of host skin cells into the composition, then the flow rate of the extruded skin-interface composition can be slowed to enable the growing and rejuvenated skin cells to enter the skin-interface composition and form skin networks. After a certain period, the networks in the skin-interface composition comprising collagen and other dermis layer structures are supportive to integrate the skin with the device.
The extruded skin-interface composition can contact with at least the epidermal and dermal layer of the skin where the skin cells are actively generating. As the skin cells grow, they can become intimately integrated into the skin-interface composition, which can be tailored to solidify into a solid, or semi-solid gel like material that provides a protective coating along the skin-device interface, prevent entry of infectious microbes and prevent device initiated inflammation at the skin-device interface 250.
As shown in
As illustrated in
In some embodiments, the bone to which a transcutaneous device can be connected, can include any bone or osseous tissue in a subject requiring fixation, support, repair, augmentation and the like. For purposes of illustration only,
In some embodiments, the percutaneous biomedical device can (having an implantable interface region 10) penetrate the skin and interface with an internal organ from the circulatory system, the auditory system, the digestive system or the nervous system. Such devices can include catheters, wires, leads sensors and other surgical or diagnostic implants that may remain partially in the patient for at least two to three weeks.
Skin Preparation and Culture Setup
Human skin was obtained from elective surgeries. Full thickness human breast skin explants from discarded material from surgeries are used. The specimens were received from healthy human subjects under University of Michigan informed consent and used immediately. After removal of subcutaneous fat, the tissue was rinsed abundantly with PBS 1X containing 125 μg/mL of gentamicin (Invitrogen/GIBCO, Carlsbad, Calif., USA) and 1.87 mg/mL of amphothericin B (Sigma-Aldrich, Milwaukee, Wis.) and placed in aliquots of the same medium for 1 hour (twice). Afterwards, the specimen was placed for another 2 hours in an incubator at 37° C. before final setup of the cultures. The culture medium used was EpiLife (Cascade Biologics, Portland, Oreg.), supplemented with EpiLife defined Growth Supplement EDGS (Cascade Biologics, Portland, Oreg.) (EDGS is an ionically balanced supplement containing purified bovine serum albumin (BSA), purified bovine transferrin, hydrocortisone, recombinant human insulin-like growth factor type-1 (rhlGF-1), prostaglandin E2 (PGE2) and recombinant human epidermal growth factor (rhEGF). In addition, the medium was supplemented with 75 μg/mL of Gentamicin and 1.125 μg/mL of amphothericin B. The final concentration of calcium used in the culture medium was 1.2 mM.
After cleaning and preparing the skin specimens, microbiological analysis of a control specimen was performed to ensure that no skin flora or other contaminants were present or remained in the explants. Microorganism analysis of the selected specimens was performed at the Microbiology Laboratory of the Burn Trauma Services at the University of Michigan Hospital. For the experiments reported, all microbiology analyses were negative. After preparation, skin specimens of approximately 1.5 cm2 were cut using a scalpel and cultured for 15 days at 37° C., 5% CO2 atmosphere in duplicate, epidermal side up at the air-liquid interface in a Transwell system consisting of 6-well Transwell carriers (Organogenesis, Canton, Mass.) and six Corning Costar supports (Fisher Scientific, Pittsburgh, Pa.). Culture media was changed every 36 hours and the stratum corneum remained constantly exposed to the air. Experiments were repeated three times, with skin from 3 different individuals (n=3). All specimens were punctured with a 3 mm diameter sterile biopsy punch (except for specific controls). Each experiment consisted of five culture plates, with four plates containing different types of control specimens.
Each culture plate had 6 wells, and each well contained one skin specimen. After cleaning, this zero day control was immediately prepared for tissue analysis as described below. The lid was designed to work with up to six reservoirs containing biological tissues and had six apertures for six percutaneous biomedical devices (six fixator pins) that formed air-tight seals to prevent contaminants from entering the reservoirs. The lids accommodated the fixator pins for use with plates PIN and PIN+BIOMAT (pin+skin-interface composition). The media for each well was changed using a small opening on the lid located next to each pin aperture, which were otherwise permanently closed. All materials were autoclaved before use in each experiment. All of the fixator pins (Stainless Steel 316, ISO 5832-9 4 mm OD and 10 cm long, (McMaster-Carr) had the same OD of 4 mm. For plates marked PIN, the pins were solid while the pins for plates PIN+BIOMAT were hollow, with a 3.6 mm ID. These hollow pins also had six orifices machined at the bottom of the pin for delivery of the biomaterial. The mixture (BIOMAT) of 0.05 wt % Dermatan Sulfate (EMD Chemicals, San Diego, Calif.) and 0.2 wt % Sodium Hyaluronate medical grade of 680 kDa. (LifeCore Biomedical, Chaska, Minn.) was prepared at room temperature and well mixed at 30° C. with a magnetic stirrer for 1 h in PBS 1X and then sterile-filtered through a 0.22 μm pore filter. A Hamilton 81320 1.0 mL syringe with a 30 gauge needle was used to deliver 100 μL of the mixture to the center of the explant puncture on specimens of plates PUNCT+BIOMAT. In specimens of plates PIN+BIOMAT the material was delivered through the top of the hollow fixator pin. The 100 μL corresponded to approximately 1.2% of the medium volume present in each well and was selected to avoid substantial increases in total volume in the culture medium. Glass tubing of 6 mm in diameter was used to cover the fixator pin aperture when the device was outside of the sterile hood to avoid bacterial contamination and was autoclaved before use in each experiment. The mixture was delivered discontinuously, at the same time that medium changes were performed, every 36 hours.
Analysis of Skin Specimens
Duplicate specimens from each plate were collected at 5 days (5D), 10 days (10D) and 15 days (15D) for analysis. Histological evaluation with haematoxylin and eosin (H&E) staining was performed for all specimens collected. For all specimens containing a perforation, tissue sections were cut from the injured areas. This type of sectioning provided the maximum viewable area of the tissue section while minimizing the distances to the pin. Blind qualitative histological analysis was performed by two independent investigators. For histological analysis, biopsies were fixed in 4% phosphate-buffered paraformaldehyde for 24 h routinely dehydrated and paraffin embedded. Serial sections were obtained at 4 μm. For light microscopy analysis, images were taken using a Nikon E800 microscope. Apoptosis and cell proliferation analyses were performed for 15D and for CNTRL+0 Day specimens in two experiments.
To analyze cell proliferation at the end of the experiment the culture medium was replaced for all specimens with fresh medium containing 400 μM/L of 5-bromo-2′-deoxyuridine (BrdU) (Sigma-Aldrich, St Louis, Mo.) and cultured for 3 hours before harvesting. Incorporated BrdU was detected by light microscopy with a horseradish peroxidase conjugated monoclonal antibody against BrdU (FrontierTM BrdU Immunohistochemistry Kit, Exalpha Biologicals, Maynard, Mass.). Four areas per slide were examined for analysis. The number of BrdU positive cells per microscopic fields was recorded and data presented as percentage of BrdU positive cells per field (mean +/−SD). Apoptotic cells were detected by labeling DNA strand breaks (TUNEL) using a commercially available kit (In SituCell Death Detection Kit, AP, Roche Diagnostics Corporation, Indianapolis, Ind.). Briefly, tissue sections were deparaffinized, rehydrated, washed in 1X PBS and labeled following manufacturer instructions, including negative and positive controls. Positive controls were prepared by incubating slides prior labeling with a solution containing 1500 U/mL of recombinant DNase I (Roche Diagnostics Corporation, Indianapolis, Ind.), 50 mM Tris-HCl, 10 mM MgCl2 and 1 mg/mL BSA for 10 minutes. Four areas per slide were examined for analysis. The number of apoptotic cells per microscopic field was recorded and data presented as the percentage of apoptotic positive cells per field (mean +/−SD).
Results
Composite microscopy images of H&E staining of human skin interfaced with pins. Panel 1 shows microscopy images of a skin specimens implanted with a fixator pin only (no extrusion of skin-interface composition was performed). Panel 2 show microscopy images taken of a skin specimen implanted with a fixator pin where a solution of physiological saline was extruded for five days. Panel 3 shows a microscopy image of a skin specimen implanted with a fixator pin where a skin-interface composition containing a solution of skin-interface composition (hyaluronic acid and dermatan sulfate) was extruded to the skin tissues for five days. Each panel contains four pictures. At the bottom of each panel there is a 2× magnification image (labeled A) showing an extended area of the tissue. The pins were located in the areas indicated. With each panel, three 20× magnification pictures are shown, two from areas close to the location of the pins (labeled B and C) and another from an area approximately 1 cm from the pin (labeled D).
The embodiments and the examples described herein are exemplary and not intended to be limiting in describing the full scope of the devices, compositions and methods of the present technology. Equivalent changes, modifications and variations can be made within the scope of the present technology, with substantially similar results.
This application claims the benefit of U.S. Provisional Application No. 61/063,704, filed on Feb. 5, 2008. The entire disclosure of the above application is incorporated herein by reference.
This invention was made with government support under grant W911NF-06-1-0218 awarded by the Army Research Office. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 61063704 | Feb 2008 | US |
