Dustin A. Gilbert, Ph.D. - US grants

Non-Technical Abstract:
The current COVID-19 pandemic has identified key problems in the US strategic preparedness for a national biological disaster. One of those is a shortage of N95 respirators, which provide critical protection to medical personnel as they treat infected patients. This issue is a direct consequence of the one-time-use nature of these N95 respirators; polymer fiber filters, including N95 and HEPA filters, capture and accumulate live pathogens, and so become biohazardous. In the proposed work, metallic nanowire bird?s nests and electrospun fibers are presented as approaches to resolve these problems, resulting in an improved respirator. The porous metallic nanowire bird?s nests allow air to pass through, similar to a polymer fiber filter, but the metallic surfaces possess antibacterial and antiviral qualities. As a consequence, pathogens captured in the bird?s nest are inactivated, improving the protection to medical workers and prolonging the usefulness of the respirator. The same metallic nanowires will also be integrated into a free surface electrospinning device, resulting in polymer fibers which are hairy with the antibacterial/antiviral nanowires. Electrospun respirators can be melted down in-house and re-spun into new respirators. This recycling step allows for respirators to be continuously re-used, removing the need to constantly re-stock. These efforts together may resolve the shortages of respirators in the current pandemic and present a superior filter product with bioactive components.

Technical Abstract:
This work seeks to develop reusable, bioactive filter materials for N95 respirators. Current filter materials are one-time-use and accumulate live pathogens, making them intrinsically unsanitary. We propose to respond to these problems using two approaches. In the first approach, freeze-cast metallic nanowire bird?s nests will be prepared using Ag and Cu nanowires. The porous structure of the bird?s nest allows air to pass, similar to a traditional filter, while Ag and Cu have been shown to have antibacterial and antiviral qualities as nanoparticles. Nanowires may present higher efficacy against pathogens due to their ability to puncture the cell and viral membranes. In the second approach, electrospun polypropylene fiber mats will be prepared as an alternative to traditional air-blown polymer filters. The electrospun textiles can be grown to custom fit operator?s faces providing an exceptional seal for use as a respirator. Used respirators can be melted on-site (melting temperature 210-280 °C) and re-spun, to prepare new, sanitary respirators. Incorporating nanowires into the molten polypropylene will result in polymer fibers with fine metallic nanowire hairs. As before, the metallic nanowires will confer antibacterial and antiviral qualities. The efficacy of the bird?s nest, the electrospun filter, and hybrid textile will be rapidly tested using suspensions and aerosols of bacteria and bacteriophages (viruses that infect bacteria). Escherichia coli and Bacillus subtilis will serve as non-pathogenic surrogates for Gram-negative and Gram-positive bacterial pathogens, respectively. An enveloped bacteriophage in family Cystoviridae will serve as a non-pathogenic surrogate of SARS-CoV-2. The proposed research will investigate the feasibility of nanowires as antibacterial and antiviral agents, develop a new, nanostructured filter material, and explore an alternative fabrication methodology, resulting in new materials and techniques with direct consequences to the US preparedness for biological disasters.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.