ANTIMICROBIAL COPPER OXIDE NANOPARTICLE COATED MASKS AND METHODS FOR PRODUCING THE SAME

FIELD OF THE DISCLOSURE

The present disclosure relates, generally, to protective devices against disease, and, more specifically, to facial protective devices against COVID-19 and methods associated therewith.

BACKGROUND

COVID-19, a disease caused by severe acute respiratory distress syndrome (ARDS), is a current ongoing worldwide pandemic that has affected 213 countries and resulted in over 21.7 million cases in the worldwide population [1, 2]. According to John Hopkins University (JHU), the rate of new cases increases at 10% a day and over seven hundred fifty thousand people have died from the disease [1]. After SARS-CoV and MERS-CoV, COVID-19 is the third zoonotic origin virus with the only pandemic level. The virus enters the human cells through a membrane protein called angiotensin-converting enzyme 2 (ACE2) [3], which causes vasoconstriction and blood pressure. Due to the presence of ACE2 in SARS-CoV-2 rather than SARS-CoV, the transmissibility of COVID-19 is very high [2, 4].

Patients infected by the COVID-19 virus, which may be found in the lungs, kidneys, heart, and intestines, may develop severe pneumonia and acute respiratory distress syndrome (ARDS) and exhibit common symptoms caused by the flu, such as dry cough, chest tightness, and fever [5], for example. The virus's incubation period may range from 3 to 20 days and be very difficult to contain due to the presence of asymptomatic carriers [2]. Due to a lack of quarantine, testing, and vaccine(s), the case fatality ratio (CFR) by nations ranges from 0.1% to over 25%. The known primary viral transmission of the SARS-CoV-2 is through short-range aerosols and respiratory droplets. An infected patient may quickly release the virus airborne by attachment to human secretion (e.g., fine particles and nasal/saliva droplets) or suspended fine particulates in the air by coughs, sneezes, and materials contaminated with body fluids.

Contaminated or infected aerosols particles may range from less than one μm to 10 μm in size. Data gathered through simulation suggests that particles less than one μm in size can stay in the air for a longer time. A study has suggested particles larger than five and less than five may reach the upper and lower respiratory tracts, respectively. It is also suggested the particles sizes produced from speaking and singing are petite, and that the number of particles is significantly higher with those activities than with continuous coughing [2, 6]. Consequently, the particle size and viral presence in the air for a longer time could have caused the widespread outbreak of the COVID-19 disease at a pandemic level. After discovering the transmission of influenza diseases (e.g., SARS virus, Avian bird flu, and H1N1 flu) from respiratory droplets such as saliva particles, secretions, and airborne particles, it became a vital and effective practice to use a protective mask to control and reduce the spread [7, 8].

At least in some cases, the ongoing COVID-19 pandemic may be caused by viral aerosols that range from 60-140 nm with a mean size of 100 nm (i.e., nano-aerosol) and are transmitted through respiratory droplets that spread into the air and onto other persons during coughs, sneezes, and talks [9]. The World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), and other governmental health organizations have recommended using N95 (Filtering Facepiece Respirator) FFR standard personal protective face masks for frontline healthcare professionals [10, 11]. According to the National Institute of Occupational Safety and Health (NIOSH), the standard N95 filtration is based on protection against particles as small as 80 nm with 95% filtration efficiency [12]. With the COVID-19 particle size being in the range of 1 the N95 FFR is the only available personal protection mask. KN95 (China), KF94 (South Korea), and FFP2 (European Union) are other filtration standards that are equivalent to the N95. Although the NIOSH has standardized N95, N99, and N100 respirators set at 300 nm aerosol [13], a standardized filter or a technology for capturing airborne viruses at sub 100 nm aerosols efficiency has yet to be discovered.

In contrast, surgical masks recommended by the CDC for use in hospitals merely protect healthcare professionals from contamination by blocking saliva particles and respiratory secretions rather than airborne particles. Their protection against viruses is not sufficient. While N95 masks have higher filtration efficiency and offer superior protection compared to surgical masks, they are thicker, not reusable, and uncomfortable for daily use. They also increase the humidity and temperature of the inhaled air, which can cause other health issues when used long-term. The two significant performance aspects of filter efficiency involve prevention of the outward escape or the inward transport of viral particles. A well-functioning filter should have the capability to capture particles in a different range of sizes from less than 1 μm to greater than 100 μm. Modern filters are fibrous and manufactured from non-woven mats of fine fibers. Porosity, fiber diameter, and layer thickness are factors that affect the filtration of the particles, among other things. Inertial impaction, interception, and diffusion are three common “mechanical” collection mechanisms that aid in the collection of larger and smaller particle sizes. Some fibrous filters use electrostatic attraction [14].

The COVID-19 pandemic has awakened the need for filtration devices and/or methods to capture airborne viruses at sub 100 nm aerosols efficiency. Researchers across the world are now working to resolve the need for an effective method to capture saliva particles, respiratory secretions, and airborne particles.

SUMMARY

The present disclosure may comprise one or more of the following features and combinations thereof.

According to one aspect of the present disclosure, a method of producing a composite article may include providing a nonwoven fabric substrate having a surface, electrospinning a nylon solution on the surface of the nonwoven fabric substrate to coat and/or impregnate the nonwoven fabric substrate with a nylon fiber, and electrospraying a modified copper oxide nanoparticle onto a surface of the nylon fiber to covalently link the modified copper oxide nanoparticle and the nylon fiber.

In some embodiments, the nonwoven fabric substrate may be a meltblown nonwoven fabric.

In some embodiments, the nonwoven fabric substrate may be a spunbond nonwoven fabric.

In some embodiments, the nonwoven fabric substrate may be a meltblown-spunbound composite.

In some embodiments, the nonwoven fabric substrate may comprise polypropylene.

In some embodiments, the electrospinning may be multi-nozzle electrospinning.

In some embodiments, the nylon fiber may be nylon 6.

In some embodiments, the electrospun nylon fiber may have a diameter from about 10 nm to about 100 nm.

In some embodiments, the modified copper oxide nanoparticle may be functionalized with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and covalently bonded to 4-hydroxyphenylboronic acid (4-HPBA).

In some embodiments, electrospraying the modified copper oxide nanoparticle onto the surface of the nylon fiber may include electrospraying the modified copper oxide nanoparticle onto the surface of the nylon fiber in a uniform field.

In some embodiments, the covalent bond that links the modified copper oxide nanoparticle to the nylon fiber may be irreversible.

In some embodiments, one or more modified copper oxide nanoparticles may be randomly oriented on the surface of the nylon fiber.

In some embodiments, the electrospraying may be multi-nozzle electrospraying.

In some embodiments, the electrospinning and the electrospraying may be performed simultaneously.

In some embodiments, the electrospun nylon fiber may form a single layer nanoscaffold having a thickness from about 1 μm to about 10 μm.

In some embodiments, the electrospun nylon fiber may form a multi-layer nanoscaffold.

In some embodiments, the electrospun nylon fiber may form a nanoscaffold having a pore size of about 50 nm.

In some embodiments, the composite article may have a virus filtration of about 99.99%.

According to another aspect of the present disclosure, a method of producing a composite article may include providing a nonwoven fabric substrate having a surface and electrospraying a modified copper oxide nanoparticle directly onto the surface of the nonwoven fabric substrate, wherein the nonwoven fabric substrate may be a meltblown nonwoven fabric.

According to yet another aspect of the present disclosure, a method of producing a composite article may include providing a nonwoven fabric substrate having a surface and electrospraying a modified copper oxide nanoparticle directly onto the surface of the nonwoven fabric substrate, wherein the nonwoven fabric substrate may be a spunbond nonwoven fabric.

These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements.

FIG. 1 is a diagrammatic depiction of a process for producing a facial protective mask/filter incorporating nonwoven fabric materials and one or more modified copper oxide nanoparticles;

FIG. 2 is a Scanning Electron Microscope (SEM) image of a nylon nanoscaffold electrodeposited with copper oxide nanoparticles to create a filter with enhanced efficacy for capturing contaminated particles and/or secretions;

FIG. 3 is a diagrammatic depiction of a process for making nylon nanoscaffolds (see images (a) and (b)) through electrospinning and a Scanning Electron Microscope (SEM) image of electrosprayed copper oxide nanoparticles (see image (c));

FIG. 4 is a schematic depiction of a multi-nozzle nanoscaffold filter enhancement system through electrospinning of nylon nanofibers with electrospraying of functionalized copper oxide nanoparticles;

FIG. 5 is a multi-view depiction of (i) an enhancement technique for the mask/filter by a compatible roll-roll process using stations (see images (a) and (b)) having rolls for unrolling the filter before electrospinning/electrospraying and rolls for rolling the filter after electrospinning/electrospraying and (ii) optimization and fabrication of a multi-nozzle vertical electrospinning/electrospraying system (see image (c)) for production of 50-100 nm nylon/copper oxide nanoparticle nanoscaffolds;

FIG. 6 is a schematic depiction of a modified copper oxide nanoparticle functionalized with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and bonded to 4-hydroxyphenylboronic acid (4-HPBA);

FIG. 7 is a diagrammatic representation of a single nozzle electrospinning device (see image (a)), a representation of the distribution of the electric field intensity from a Taylor cone at a nozzle tip with an angle width of 98.6° generating a uniform plume (see image (b)), and a representation of the static electric field of the nozzle (see image (c));

FIG. 8A is a schematic depiction of an irreversible chemical covalent bonding of copper oxide nanoparticles with nylon according to the concepts of the present disclosure;

FIG. 8B is a schematic depiction of a nanofilament interaction between copper oxide nanoparticles and nylon;

FIG. 9 is a graphical representation of Zeta potential measurements of bare (on the right) and surface functionalized (on the left) copper oxide nanoparticles;

FIG. 10 is a graphical representation of the results of Energy Dispersive X-ray (EDX) analysis of electrospun nylon-6 fibers coated with copper oxide nanoparticles;

FIG. 11A is a Scanning Electron Microscope (SEM) image of electrospun Nylon-6 fibers;

FIG. 11B is a Scanning Electron Microscope (SEM) image of electrosprayed copper oxide nanoparticles;

FIG. 11C is a Scanning Electron Microscope (SEM) image of electrosprayed copper oxide nanoparticles on electrospun Nylon-6 fibers;

FIG. 12 is a depiction of multiple Scanning Electron Microscope (SEM) images of nanoscaffold designs including PLA-Polylactic acid (see image (a)), PEO-Polyethylene oxide (see image (b)), Chitin and Chitosan (see image (c)), Particle dispersed polymers (see image (d)), PAN-Polyacrylonitrile (see image (e)), PA6 Nylon (see image (f)), PVA-Polyvinyl alcohol (see image (g)), and PU-Polyurethane (see image (h));

FIG. 13 is a depiction of high-efficiency particular air (HEPA) filters;

FIG. 14 is a depiction of removal efficiency of various air filters;

FIG. 15 is a schematic depiction of the production of nanofibrous membranes including nylon-6 fibers coated with copper oxide nanoparticles;

FIG. 16 is a depiction of SEM images of electrospun nylon-6 fibers, electrosprayed copper oxide nanoparticles, and electrosprayed copper oxide nanoparticles on electrospun nylon-6 fibers;

FIG. 17 is a schematic depiction of a multi-nozzle nanoscaffold filter medium enhancement system;

FIG. 18 is a depiction of a roll-roll electrospinning/electrospraying machine;

FIG. 19 is a multi-view depiction of (i) an enhancement technique for the mask/filter by a compatible roll-roll process using stations (see images (a) and (b)) having rolls for unrolling the filter before electrospinning/electrospraying and rolls for rolling the filter after electrospinning/electrospraying and (ii) optimization and fabrication of a multi-nozzle vertical electrospinning/electrospraying system (see image (c)) for production of 50-100 nm nylon/copper oxide nanoparticle nanoscaffolds;

FIG. 20 is a schematic depiction of the functionalization of copper oxide nanoparticles and functionalized copper oxide nanoparticles bonded with nylon-6 fibers;

FIG. 21 is a depiction of a setup for testing airflow of filtration devices;

FIG. 22 is a depiction of a setup for testing adherence of copper oxide particles to a substrate;

FIG. 23 is a depiction of a system for analyzing adherence data of copper oxide particles to a substrate;

FIG. 24 is a graphical depiction of air flow toxicity tests conducted for various HEPA fabrics;

FIG. 25 is a graphical depiction of adherence tests conducted for various HEPA fabrics;

FIG. 26 is a depiction of SEM images of air flow toxicity tests conducted for copper oxide particles with isopropyl alcohol and polyvinylpyrrolidone (PVP);

FIG. 27 is a depiction of SEM images of air flow toxicity tests conducted for copper oxide particles with methanol;

FIG. 28 is a depiction of SEM images of air flow toxicity tests conducted for copper oxide particles with methanol and PVP;

FIG. 29 is a diagrammatic depiction of a project roadmap and commercialization strategy;

FIG. 30 is a depiction of SEM images of HEPA filter media enhancement achieved through the use of electrosprayed copper oxide nanoparticles on electrospun nylon-6 fibers; and

FIG. 31 is a depiction of SEM images of HEPA filter media enhancement achieved through the adjustment of pore sizes of electrosprayed copper oxide nanoparticles on electrospun nylon-6 fibers.

DETAILED DESCRIPTION

While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one A, B, and C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).

In the drawings, some structural or method features may be shown in specific arrangements and/or orderings. However, it should be appreciated that such specific arrangements and/or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and/or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, may not be included or may be combined with other features.

A number of features described below may be illustrated in the drawings in phantom. Depiction of certain features in phantom is intended to convey that those features may be hidden or present in one or more embodiments, while not necessarily present in other embodiments. Additionally, in the one or more embodiments in which those features may be present, illustration of the features in phantom is intended to convey that the features may have location(s) and/or position(s) different from the locations(s) and/or position(s) shown.

As used herein, the term “nanostructure” refers to an elongated chemical structure having a diameter on the order of nanometers and a length on the order of microns to millimeters, at least in some embodiments. In such embodiments, each nanostructure may have an aspect ratio greater than 10, greater than 100, greater than 1000, or greater than 10,000. In some cases, the nanostructure may have a diameter less than 1 μm, less than 100 nm, less than 50 nm, less than 25 nm, or less than 10 nm. Additionally, in some cases, the nanostructure may have a diameter less than 1 nm. Typically, the nanostructure may have a cylindrical or pseudo-cylindrical shape. In some embodiments, the nanostructure may be a nanotube, such as a carbon nanotube.

It should be appreciated that the nanostructures described herein may be uniformly dispersed within various matrix materials, which may facilitate formation of composite structures having improved mechanical, thermal, electrical, or other properties, among other things. Methods contemplated by the present disclosure may also allow for continuous and scalable production of nanostructures, such as nanotubes, nanowires, nanofibers, and the like, for example, on moving substrates, at least in some cases.

In some embodiments, substrates described herein may be prepregs. That is, the substrates may include a polymer material (e.g., a thermoplastic polymer) containing embedded, aligned, and/or interlaced (e.g., woven or braided) fibers such as carbon fibers. As used herein, the term “prepreg” refers to one or more layers of thermoplastic resin containing embedded fibers, such as fibers of carbon, glass, silicon carbide, and the like, for example.

The use of facial masks has become omnipresent worldwide since the outbreak of severe respiratory diseases caused by the new coronavirus (COVID-19). Consequently, the world is currently experiencing a shortage of face masks, and some countries have placed restrictions on the number of masks that any individual can purchase. While the N95 surgical grade mask offers the highest degree of safety currently available, due to its broader pore size (almost 300 nm), its filtration capacity for sub-300 nm particles is about 85%. Since the COVID-19 virus has a diameter of about 65-125 nm, more effective reusable masks are required.

The need to control the spread of coronavirus has resulted in a surge in demand for surgical masks across the globe [12, 13]. Surgical mask manufacturers in North America are ramping up their production to meet the unprecedented demand [14]. Also, addressing the challenge around the growing shortage of surgical masks in Europe, several countries including the United States are providing surgical masks and coronavirus testing kits to help European countries combat the pandemic [2, 4, 15]. The mask market is also driven by a worldwide concern for reducing future outbreaks of epidemics. In addition, the rising number of surgical procedures is anticipated to boost the growth of the mask market.

Factors such as poor sanitization, poor immunity among people, and delays in implementing control measures to contain the spread of flu and other diseases may lead to future global pandemics [16-18]. The COVID-19 pandemic is one such recent example. It is believed to have originated sometime last September and since then has spread to almost every country around the world. Healthcare professionals and governments across the world are recommending the use of masks to control the spread of this virus. Apart from public use, surgical masks are extensively used by physicians, nurses, social workers, housekeeping staff, and others at a high risk of exposure to airborne diseases including influenza, viral meningitis, and measles, among others. These diseases spread through liquid droplets suspended in the air when an infected person coughs or sneezes. Therefore, the increasing frequency of epidemics is expected to boost the growth of the market for masks/filters in the future.

At this time, the U.S. Food and Drug Administration (FDA) has not approved any type of surgical mask specifically for protection against the coronavirus due to their large pore size. Although N95 masks offer the highest level of protection currently available after N99 and N100, they only filter about 85% of particles smaller than 300 nm [19], meaning that coronavirus particles can slip through these coverings. Also, because of shortages, many health care workers have had to wear the same N95 mask repeatedly, even though they are intended for a single use, which can be very hazardous [7]. Cloth masks are easy to find and can be washed and reused. Asking everyone to wear cloth masks may help reduce the spread of the coronavirus by people who have CON/ID-19 but do not realize it. Cloth masks are cheap and simple to make, however, they do not provide as much protection for the wearer even if they utilize multiple layers of fabric [20]. Some cloth masks are fabricated to include an additional filter pocket [21]. Due to the shortage and high cost of N95, N99, and N100 masks, enhancing surgical masks and cloth masks with filter pockets remains an area of interest.

The methods and associated devices disclosed herein enhance the filtration efficiency and antiviral performance of masks to over 99.99% by depositing a thin layer of nylon/CuONPs nanoscaffolds in between the mask layers or fabric. The methods of the present disclosure are effective at increasing the comfort and safety of protective masks/filters while simultaneously increasing the airflow and filtration efficiency due at least in part to the provision of a large volume to surface ratio and a 3D porous medium. In addition, such nanoscaffold deposition significantly increases antiviral efficacy thereby reducing cross-contamination and enabling reusability.

The present disclosure demonstrates and envisions the creation of a nanoporous flexible copper oxide enhanced electrospun Nylon-6 membrane on a regular fabric filter layer with enhanced filtration performance and reusability in order to address the shortcomings of existing COVID-19 protective devices. Because of desirable antimicrobial properties and economical production, copper oxide has been selected as an antibacterial agent compared to other metal nanoparticles used as antibacterial agents. On regular fabric, which is used as a filter layer in N95 surgical masks, the present disclosure contemplates the deposition of a thin layer of electrospun Nylon-6 nanofibers coated with functionalized Copper Oxide nanoparticles by an electrospraying technique.

Prepared nanofibers composites of the present disclosure have been characterized for future research. That characterization may include, but is not limited to, morphological characterization, surface area and porosity estimation using BET, mechanical properties characterization using a Universal Testing Machine, elemental analysis using XPS, crystallinity evaluation by XRD, upright cup breathability examination, air permeability monitoring, thermal analysis by TGA, and disinfectant antimicrobial properties. Excellent morphological, mechanical, structural, surface, and antimicrobial properties were observed in Nylon-6 fibers coated with copper oxide nanoparticles (amount of CuO in the Nylon-6 fibers has been estimated to be 3-5 wt. %)

Among other things, the present disclosure demonstrates a commercially viable and scalable methodology that uses electrospinning nanotechnology to electrospin nylon nanoscaffold facial masks and filters with an adjustable pore size of as small as 50 nm. The process/methodology for producing a facial protective mask/filter incorporating nonwoven fabric materials and one or more modified copper oxide nanoparticles consistent with the teachings of the present disclosure is diagrammatically depicted in FIG. 1. The nanoscaffold masks and filters achieved by simultaneous electrospraying of copper oxide nanoparticles (CuONPs) onto electrospun nylon as envisioned by the present disclosure offer excellent morphology and are largely free of defects. The process contemplated herein enables fabrication of mask and filter fabrics with higher filtration efficiency (including sub 100 nm efficiency), lower air resistance, and antiviral properties that offer effective protection against COVID-19 and enhanced comfort for daily use. As described in greater detail below, the process is accomplished using antiviral copper oxide nanoparticle (CuONPs)-coated electrospun nylon nanoscaffolds. The nanoscaffold layer of the facial masks and filters disclosed herein noticeably improves performance by lowering air resistance while trapping and disabling viral particulates in the breathing air stream.

Commercial entities capable of (i) manufacturing electrospun nylon nanoscaffold filters with an adjustable pore size as small as 50 nm and (ii) simultaneous electrospraying of CuONPs are quite limited. Incorporation of ultra-fine CuONP-enhanced nanoscaffold layers that are deposited on a thin melt-blown fabric likely assures notable improvements in virus filtration (e.g., over 99.99% efficacy compared to 95% efficacy in N95 masks), as well as improved airflow. It is envisioned that the CuONP filter layers produced in single or multiple layers of electrospun nanofibers on a fabric substrate as disclosed herein will have a higher grade efficiency which can be substantiated using an aerosolization filter tester to simulate the known COVID-19 virus particle size range (e.g., 60 to 140 nm). Small-diameter nanofibers (e.g., 50-100 nm) will likely lead to higher mechanical capture by diffusion and interception. In contrast to typical two-dimensional micropores, which dominate construction of typical layered fiber masks, the use of multilayer scaffolds may reduce the pressure drop across the membrane significantly as a result of introducing three-dimensional nanopores.

The process/methodology disclosed herein for producing the nylon/CuONP nanoscaffold layers adds a single manufacturing operation that can be performed by all current users of filter rolls with minimal change in their mask/filter fabrication processes. In addition to antiviral capability, as a result of the improved filtration efficiency, masks/filters contemplated by the present disclosure may be manufactured with thinner and lighter fabric layers while exceeding existing airflow criteria and improving comfort.

Previous attempts to overcome existing filtration weaknesses have utilized methods and/or techniques that are undesirably costly and complex. Additionally, such attempts have mostly involved mechanical trapping, which reduces airflow and provides no antiviral capabilities. The few “antiviral” masks resulting from those efforts do not incorporate electrospinning technology, demonstrate only limited increases in filtration efficiency, and offer minimal improvements in airflow.

The method of producing CuONP scaffold layers contemplated herein may be implemented on a small scale using a single nozzle. That method may include, or otherwise be embodied as, the following tasks: 1) optimizing the nanoscaffold filter manufacturing process, 2) designing and fabricating a multi-nozzle vertical electrospinning and electrospraying system to complete a prototype antiviral enhanced mask/filter, and 3) manufacturing and testing coupons using the ventilation systems.

The nanoscaffold enhanced antiviral filters of the present disclosure offer robust protection and reusability, which may provide opportunities to target consumers of surgical masks that have thus far yet to be served. The filter enhancement techniques envisioned by the present disclosure may add less than 5 cents per square foot of material cost as both nylon and CuONPs are relatively inexpensive and available in large quantities, leading to new potential market opportunities.

One particular advantage of the methods/processes of the present disclosure is the relatively seamless integration of those methods into existing manufacturing processes. In addition, the antiviral properties of the protective devices disclosed herein may reduce cross-contamination and lessen the need to dispose of masks after each use while achieving high levels of protection and improved air flow, comfort, breathability, and efficiency at an industrial level. Due to the embedding of CuONPs nanoscaffold enhanced layers onto existing fabric or filter rolls, the enhanced antiviral and filtration efficiency of protective devices disclosed herein may lead to the fabrication of more durable and more efficient filter products without significant changes in manufacturing processes.

Filter layers made of CuONPs deposited on nanoscaffolds as contemplated by the present disclosure may have more than 99.99% efficiency in trapping and disabling viruses such as coronavirus. Their high surface area per unit volume may enhance virus capture efficiency and significantly shorten viral viability due to the integration of CuONPs. The capture mechanism is illustrated in FIG. 2. Among other things, the present disclosure is directed to the design and demonstration of a manufacturing process for nylon nanoscaffolds with CuONPs coatings for use in reusable facial masks/filters. FIG. 3 is a schematic of a nanoscaffold enhanced filter layer coating system and associated roll-roll manufacturing approach. According to the present disclosure, nanoscaffolds of electrospun nylon with associated electrosprayed CuONPs can be applied onto any fabric of interest to enhance virus protection and create reusable facial masks/filters suitable for protection against COVID-19 and other viruses. To do so, one nozzle for electrospinning polymers into nanofibers and another nozzle for electrospraying a uniform field of CuONPs are disclosed herein.

In some embodiments, apparatuses, techniques, and/or parameters associated with the methodologies and protective devices of the present disclosure may include, or otherwise be embodied as, the following: (i) vertical electrospinning; (ii) 8 concurrently feeding nozzles; (iii) 500 mm width nanoscaffold deposition; (iv) programmable control panel for parameter adjustment; (v) continuous roll-roll cloth winding collector system; (vi) adjustable horizontal movement between 20-80 mm; (vii) adjustable spinning distance between nozzles to cloth of 50-300 mm; (viii) 1-10 μm thick nanoscaffold thickness production capacity; and (ix) two programmable syringe pumps and one high voltage power supply. Additionally, in accordance with the present disclosure, characterization of nanoscaffolds of electrospun nylon with associated electrosprayed CuONPs may include, or otherwise be embodied as, the following: (a) fiber morphology (scanning electron microscopy (SEM) and X-ray diffraction (XRD)); (b) fiber diameter (automated image analysis software); (c) pore size (porometry and mathematical modeling); (d) porosity (porometry, liquid intrusion, and gravimetric measurement); (e) surface wettability (contact angle); (f) structural integrity (micro-CT (computer tomograph) scan); (g) glass transition temperature (differential scanning calorimetry); (h) surface chemistry (fourier transform infrared (FTIR), raman, X-Ray photoelectron spectroscopy); (i) residual solvent (gas chromatography mass spectrometry); (j) gaseous component (thermogravimetry (TGA) in conjunction with FTIR); (k) molar mass analysis (size exclusion chromatography); (l) pressure drop and air flow rate measurements; (m) water vapor transfer rate; (n) nanoparticle filtration efficiency; and (o) persistence and infectivity of viral/bacterial challenges to CuONP embedded electrospun layers. In any case, a process schematic of a multi-nozzle nanoscaffold filter enhancement system for applying nanoscaffolds of electrospun nylon with associated electrosprayed CuONPs onto a non-woven fabric is depicted in FIG. 4.

In some embodiments, the process and design optimization of the nylon masterbatch and the multi-nozzle system depicted in FIG. 4 may be associated with contemporaneous implementation of a roll-roll system needed for the continuous deposition of nanoscaffolds onto fabric rolls. That roll-roll system is shown in FIG. 5. Scalability to render the setup suitable for production line settings and R&D projects is one important consideration. In some embodiments, the multi-nozzle system may include 8 nozzles to enable high productivity for the mass production of nanofibers and their coating with CuONPs. Of course, it should be appreciated that in other embodiments, the multi-nozzle system may function with fewer nozzles, such as when working on R&D projects, for example. In any case, the unique design of the multi-nozzle system enables production of nanoscaffolds with two rows of syringes that are independently controlled.

In some embodiments, the multi-nozzle and roll-roll systems of the present disclosure may be capable of production at a rate of 5 m/hr and a roll width of 500 mm. Additionally, in some embodiments in which a larger production scale is desired, production at a rate of 60 m/hr and a roll width of 1,500 mm may be attainable. Additionally, in some embodiments still, production using an electrospinning/electrospraying station including up to 50 nozzles arranged in 5-8 rows may be feasible.

Nylon Batch Preparation

Nylon was selected as the material for nanoscaffold fabrication due in part to its availability, low cost, ease of use, and the presence of active carbonyl groups on the surface capable of bonding to the functionalized CuONPs. According to one batch preparation method of the present disclosure, Nylon 6 pellets were received from Sigma-Aldrich, USA (product #181110). The molecular weight of the Nylon 6 was 10,000 g·mol⁻¹and the bulk density was 1.084 g·mL⁻¹. Formic acid with a purity of 88% was obtained from Fisher Scientific, USA (product #A118P-500). All the materials were used as received without further purification. Nylon 6 pellets were dissolved in 88% formic acid at concentrations of 10%, 15% and 20% wt. Thereafter, the container was wrapped by Parafilm tape to prevent the evaporation of formic acid. The as-prepared solutions were mixed under magnetic stirring at room temperature for 24 h to form clear solution. Lastly, the solutions were sonicated for 30 mins to ensure complete dispersion of Nylon 6 pellets.

According to another batch preparation method of the present disclosure, nylon nanofibers may be made from a masterbatch consisting of the polymer resin (15% v/v) dissolved in formic acid which can be deposited onto any cloth material of interest. The diameter of the nylon filaments may be selected to generate nanoscaffolds having pore sizes in the range of 50-100 nm to preclude the passage of virus particles while allowing comfortable breathing airflow. Samples may be prepared by mixing the masterbatch and DMF (1:4 volume ratio) for 10 min using a magnetic stirrer, followed by probe sonication for 10 min in intervals of 45 s with 30 s rest cycles between. Triton X-100 may be added into the mixture in the ratio 20:1 and stirred for 10 min, followed by sonication in the same manner as described before. Neat nylon may then be added in the same weight as masterbatch and stirred for 15 min, followed by the same sonication method. The mixture may then be degassed in a vacuum oven at room temperature for 15 min. Prior to spinning, the prepared solution may be placed into a syringe with a needle gauge of 26 G.

Surface Functionalization of CuONPs by GLYMO and 4-HPBA

A recent U.S. government-funded study conducted by researchers at the National Institutes of Health (NIH) and the Centers for Disease Control and Prevention (CDC) reported that the SARS-CoV-2 virus, which causes the disease COVID-19, remains viable for up to 2 to 3 days on plastic and stainless steel surfaces vs. only 4 hours or less on copper [26]. As disclosed herein, CuONPs (high purity, 99.95+%, 25-55 nm, US Research Nanomaterials, Inc., Houston, Tex.) are functionalized with (3-glycidyloxypropyl)-trimethoxysilane (GLYMO) to allow covalent coupling of 4-hydroxyphenyl-boronic acid (4-HPBA) which also increases their antiviral effectiveness [27]. That functionalization is schematically depicted in FIG. 6.

According to one surface functionalization technique contemplated by the present disclosure, CuO nanoparticles (10 nm) purchased from US Research Nanomaterials, Inc may be stored in an Argon-filled glovebox to avoid moisture contamination. Initially, 1 g of CuONPs may be dispersed into 1 liter of deionized water and the pH level measured. If the measured pH was not within the range of 6-6.5, dilute HCl or NaOH may be added dropwise to adjust the pH. Then, the solution may be kept on the hot plate with magnetic stirrer (600 rpm) for an hour and 0.1 wt % of GLYMO subsequently added to the solution. The suspension may be stirred for another 24 hours. Later, the unreacted GLYMO may be removed by three times centrifugation (10,000 rpm, 10 mins) and washing by DI water. Thereafter, GLYMO functionalized CuONPs may again be dispersed into 1 liter of DI water and 1 g of 4-HPBA already dissolved in 1 liter of ethanol may be added dropwise to the former solution. The resulting mixture may be shaken for 2-3 hours with a vortex shaking device. Finally, the total solution may be centrifuged (10,000 rpm, 30 mins) and washed three times with ethanol. 0.05 g of PVP (3,6000 MW) may be added to 9 ml of IPA solution and stirred for 10 mins until all PVP dissolved in it. The CuONP precipitate from the centrifuge tube may be collected and dispersed into the IPA-PVP solution. The final mixture may be kept in high power ice bath sonication for 90 minutes followed by probe sonication (30% amplitude) for 2 hours. Finally, the solution may be centrifuged (4,000 rpm, 30 mins) to remove undispersed functionalized CuONPs. The resulting functionalized CuONPs dispersed into IPA may be stored in 10 ml of BD syringe.

Electrospinning of Nylon-6 and Electrospraying of CuONPs

The electrospinning mechanism is important for system performance to ensure a uniform scaffold for deposition of CuONPs and thereby to enhance airflow as a consequence of that uniformity. At least in some embodiments, the electrospinning station should be capable of manufacturing ultra-long nylon nanofibers with high surface to volume ratio. To achieve uniform deposition of nylon/CuONPs, a uniform high voltage electric field may be required, at least in some embodiments.

The electric field may be simulated using Finite Element Analysis (FEA) followed by experimental optimization to obtain a uniform electric field from strategically placed nozzles. With respect to the nylon nanofibers, multiple parameters may be varied, such as the straight length of the filament after spinning and before bending, the electrospun filament's initial angle, helical pitch, and bending frequency, for example. For the nylon/CuONP deposition, the length of the needles beneath the collector electrode, the distance between the electrodes, and their overall arrangement may be varied to investigate their effects on fiber morphology and diameter and NP uniformity. ANSYS software may be used to analyze the 3D electric field.

The electric field strength and the non-uniformity factor of an individual nozzle may be used to define the requirements for the overall electric field. Image (a) shown in FIG. 7 illustrates the schematic of a single nozzle electrospinning device set-up for enhancement of the masks/filters demonstrating a more than 75% improvement in filtration efficiency. That improvement was achieved when the overall electric field at the negative plate was kept uniform (i.e., as shown in image (b) of FIG. 7) and where the peak of the electric field intensity appeared at the nozzle orifice and was estimated to be E=2.75 MV/m (i.e., as shown in image (c) of FIG. 7).

Prior to the electrospinning process, the Nylon-6 solution prepared as discussed above may be sonicated for an additional 5 min to ensure complete dispersion. The prepared solutions may be loaded into 10 mL BD syringes with eccentric tips and placed on a syringe pump. Needles may be attached to the syringe. The grounded collector may be a flat rectangular metal plate (15×20 cm) covered with fabric. The needle tip to collector distance may be 12 cm and the pumping rate may be 0.05 ml/h. A high voltage of 25 kV may be applied for electrospinning. The anode may be fixed on the needle and the cathode may be fixed on the collector. Each sample may be electrospun for 20 min to make sure that the thickness of the mat would be in the range of 10 to 15 μm.

While performing the electrospinning of Nylon-6, electrospraying of CuONPs may be performed via an arrangement similar to the arrangement depicted in FIG. 4. A 10 ml BD syringe containing CuONPs solution may be attached in a syringe pump device. Electrospraying parameters may be optimized as follows: 10 KV power supply, 0.15 ml/h feeding rate, 27 G needle size, and a distance between the needle tip and collector of 12 cm. Electrospinning of Nylon-6 and electrospraying of CuONPs may be performed simultaneously so that all fibers are properly coated by CuONPs.

In some embodiments, NaCl may be added to increase the electrical conductivity of the functionalized CuONPs suspension. In such embodiments, subsequent to stirring the final suspension using a magnetic stirrer for 4 h, the suspension may be electrosprayed onto the electrospun nylon nanofibers (e.g., as shown in image (c) of FIG. 3). Significantly, boronic acid (BA) groups on the surface of the functionalized CuONPs may form irreversible chemical covalent bonds with the nylon, thereby creating tetravalent or possibly trivalent coordination with the carbonyls in the nylon. A proposed mechanism for those interactions is depicted in FIGS. 8A and 8B. It is also possible that the BA groups on the CuONPs may enhance the CuONP's antiviral properties [27] as a result BA groups bonding with glycans on the SARS-CoV-2 envelope [28]. At least in some embodiments, the irreversible covalent binding of CuONPs to the nylon nanofiber surfaces as shown in FIGS. 8A and 8B may (i) facilitate uniform electrospraying on the scaffolds of nylon nanofibers to avoid agglomeration, (ii) eliminate the risk of their separation from nanoscaffolds and concomitant antiviral effectiveness loss, and (iii) offer enhanced antiviral action against SARS-CoV-2 trapped in the nanoscaffold such that the CuONPs significantly shorten its viability.

Characterization

Zeta (ζ) Potential Measurement

The isoelectric point (IEP) (the pH value where zeta (0 potential of CuONPs is zero) for CuONP may have a measured value of 9. In some cases, it has been found that the pH value higher than the IEP may be associated with a tendency of CuONPs to lose colloid stability and aggregate thereby forming relatively large chunks around 400-600 nm. To avoid this, the pH of bare and functionalized CuO may be maintained to 6-6.5 by adding dilute HCl or NaOH. Hydrodynamic diameters of pristine CuONPs and functionalized CuONPs may be around 50 nm and 80 nm, respectfully. The ζ-potential of the bare CuONPs may be −3.80 (see FIG. 9 on the right), whereas the surface-modified CuONPs may have smaller ζ-potential, ranging from −9.29 to −8.29 (see FIG. 9 on the left).

EDX Analysis

The results of EDX analysis of electrospun nylon-6 fibers coated with CuONPs are shown in FIG. 10. The EDX range illustrates the main compositions of carbon and oxygen on the nanofiber. The element of copper appears in the EDX spectrum after the Cu electrospraying operation. It is also observed that the content of copper reaches up to 3% and that the content of oxygen increases significantly after the Cu deposition.

Surface Morphology

The SEM images in FIGS. 11A-11C display structures and surface characteristics of the electrospun PA6 nanofibers without (see FIG. 11A) and with Cu layer (see FIG. 11C). The images show the three-dimensional fibrous structures of the PA6 nylon nanofibers. The nanofibers have diameters varying from less than 100 nm to 150 nm, at least in some embodiments. The nylon nanofibers maintain their porous structures but the Cu nanoparticles are randomly oriented, at least in some embodiments.

In some embodiments, any one of a number of filaments may be used for the electrospinning operation contemplated herein. SEM images of nanoscaffolds formed in various nanofilaments are depicted in FIG. 12. Those images include PLA-Polylactic acid (see image (a)), PEO-Polyethylene oxide (see image (b)), Chitin and Chitosan (see image (c)), Particle dispersed polymers (see image (d)), PAN-Polyacrylonitrile (see image (e)), PA6 Nylon (see image (f)), PVA-Polyvinyl alcohol (see image (g)), and PU-Polyurethane (see image (h)).

Mask/Filter Validation

Filtration efficiency testing may be carried out using sodium chloride. An aerosol generator may be used to create particle sizes of 50-500 nm to test the filter. The size range covers the particle size of SARS-CoV-2 (60-140 nm). The particle concentration may be measured by the Condensation Particle Counter (CPC) upstream of the aerosols. Subsequently, the concentration may be measured downstream of the test filter as well. Therefore, the filtration efficiency can be determined by the following equation:

$\begin{matrix} η (D_{P}) = 1 - \frac{C_{d} (D_{P})}{C_{u} (D_{P})} & (1) \end{matrix}$

where η is the grade efficiency for aerosol size D_P, C_uis the concentration upstream, and C_dthe concentration downstream of the test filter. The diameter of the test filter may be set at 3 in. The pressure drop (Δp) across the filter may also be measured. Quality factor (QF) may be defined by the following equation:

$\begin{matrix} QF = - \frac{\ln (1 - η)}{Δ p} & (2) \end{matrix}$

Testing and Validation of Antiviral Efficiency

In addition to the morphological and nanoscaffold structural testing described above, the antiviral/antimicrobial effects of the CuONPs coated nylon nanoscaffolds sprayed on melt-blown fabric and on filters may be determined. The surface may be exposed to a variety of microbial agents that include bacterial and viral inactivation assays, for example. Due to restricted access to the virus SARS-CoV-2, the surface may be tested for antimicrobial effects on surrogate biologicals including human respiratory coronavirus (ATCC® VR-2384™) [29] and MS2 (a bacteriophage). The efficiency of the facial mask/filter may be tested and validated using two methods (contact based kill and ATP based residual biological activity assays).

Contact based kill assays may be conducted in which the biological contaminant is directly applied to the modified filter surfaces and allowed to incubate under controlled conditions (i.e., controlled temperature and humidity). Samples may be assessed over time with the residual biologics being collected from the fabric by submergence in growth media. Spot plates leveraging serial dilutions to assess bacterial contaminants (e.g., BL21 E. coli) may be used to determine kill rates to calculate log bacterial reductions. Viral inactivation may follow a similar experimental design with the collected solution being added to the confluent bacterial plates (e.g., MS2 virus) utilizing plaque number (areas of bacterial death) and cell viability assays (porcine respiratory coronavirus) to assess residual viral activity following contact with the CuONPs coated nylon nanoscaffolds. All assays may be conducted with unmodified nylon fibers as a control. These initial kill assays may guide the optimization of copper surface coverage and development of further antimicrobial assays following mask capture efficiency of aerosolized virus.

Additional biological activity assays for residual bacteria to assess antimicrobial effects of the surface may include colorimetric ATP based assays, among others. These assays may measure residual biologic activity on surfaces as related to the amount of ATP present. They may be carried out similarly over a predetermined surface exposure time to assess bacterial inactivation on functionalized and non-functionalized surfaces.

Results and Discussion

The average size of CuONPs is significant to the potential antimicrobial action, since smaller nanoparticles are more compact and have the capacity to penetrate and migrate within bacterial cells. The size of CuONPs therefore contributes to the success and efficacy of the antimicrobial nanoparticles. The existence of another form of anionic substances (e.g., organic acids, albumins, surfactants, polymers, and others) in the solution may, therefore, quickly inhibit electrostatic adherence. This may influence the association of nanoparticles with various biomolecules, such as carbohydrates and proteins, for example, that can be adsorbed to the particles to create specific surface properties that may be different from the properties of the initial nanoparticles. Such adsorption may explain why CuONPs can lose their antimicrobial function quickly in biological fluids and formulations of anionic polyelectrolytes and surfactants.

In the present disclosure, CuONPs with boronic acid (BA) surface functionality have been developed in an effort to provide a non-electrostatic mechanism for their bacterial binding that is intended to enhance their cell wall aggregation in the presence of other anionic organisms. In accordance with the teachings of the present disclosure, added surface groups of boronic acid (BA) on the CuONPs may covalently bind to different glycoproteins and carbohydrates that prevail on the bacterial cell walls. Boronic acid has been used in chemosensor systems because of its strong sensitivity to sugar determination. The perceived absence of toxicity of BA, even with its capability to form reversible covalent complexes with diols, makes BA a superficial feature that is efficient in biomedical applications. The binding of BA to sugar is sensible to sugar but non-discriminatory, and thus BA binds to diol which contains compounds. BA has been recognized as a useful compound for quantifying the total number of bacteria. BA surface groups may bind covalently and form boronic esters with saccharides. The function of CuONPs as an outside monolayer may contribute to their covalent binding onto the membrane surface of the membrane groups of sugar (OH), thereby putting the CuONPs close to the bacterial cell membrane and increasing their effectiveness.

REFERENCES

[1] Dong, E., H. Du, and L. Gardner, An interactive web-based dashboard to track COVID-19 in real time. Lancet Infect Dis, 2020. 20(5): p. 533-534.

[2] Liao, L., et al., Can N95 Respirators Be Reused after Disinfection? How Many Times? ACS Nano, 2020. 14(5): p. 6348-6356.

[3] McLachlan, C. S., The angiotensin-converting enzyme 2 (ACE2) receptor in the prevention and treatment of COVID-19 are distinctly different paradigms. Clinical Hypertension, 2020. 26(1): p. 14.

[4] Baud, D., et al., Real estimates of mortality following COVID-19 infection. The Lancet Infectious Diseases, 2020. 20(7): p. 773.

[5] Letko, M., A. Marzi, and V. Munster, Functional assessment of cell entry and receptor usage for SARS-CoV-2 and other lineage B betacoronaviruses. Nature Microbiology, 2020. 5(4): p. 562-569.

[6] Yan, J., et al., Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. Proceedings of the National Academy of Sciences, 2018. 115(5): p. 1081-1086.

[7] Jefferson, T., et al., Interventions for the interruption or reduction of the spread of respiratory viruses. Cochrane Database of Systematic Reviews, 2007(4).

[8] Jefferson, T., et al., Physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review. BMJ, 2008. 336(7635): p. 77-80.

[9] Leung, W. W. F. and Q. Sun, Electrostatic charged nanofiber filter for filtering airborne novel coronavirus (COVID-19) and nano-aerosols. Separation and Purification Technology, 2020. 250: p. 116886.

[10] Aledort, J. E., et al., Non pharmaceutical public health interventions for pandemic influenza: an evaluation of the evidence base. BMC Public Health, 2007. 7(1): p. 208.

[11] Centers for Disease Control and Prevention. Interim Guidance for Protection of Persons Involved in U.S. Avian Influenza Outbreak Disease Control and Eradication Activities. 2019; Available from: https://www.cdc.gov/niosh/emres/2019_ncov_default.html.

[12] Eninger, R. M., et al., Filter Performance of N99 and N95 Facepiece Respirators Against Viruses and Ultrafine Particles. The Annals of Occupational Hygiene, 2008. 52(5): p. 385-396.

[13] NIOSH-Approved Particulate Filtering Facepiece Respirators. 2020 08/17/2018]; Available from: https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/default.html.

[14] Lisa Brosseau, S., and Roland Berry Ann, N95 Respirators and Surgical Masks. 2020, Centers for Disease Control and Prevention.

While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

All publications, patents, and patent applications referenced herein are hereby incorporated by reference in their entirety for all purposes as if each publication, patent, or patent application had been individually indicated to be incorporated by reference.

ANTIMICROBIAL COPPER OXIDE NANOPARTICLE COATED MASKS AND METHODS FOR PRODUCING THE SAME

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