Study of the Pathogen Inactivation Mechanism in Salt-Coated Filters.

As COVID-19 exemplifies, respiratory diseases transmitted through aerosols or droplets are global threats to public health, and respiratory protection measures are essential first lines of infection prevention and control. However, common face masks are single use and can cause cross-infection due to the accumulated infectious pathogens. We developed salt-based formulations to coat membrane fibers to fabricate antimicrobial filters. Here, we report a mechanistic study on salt-induced pathogen inactivation. The salt recrystallization following aerosol exposure was characterized over time on sodium chloride (NaCl), potassium sulfate (K2SO4), and potassium chloride (KCl) powders and coatings, which revealed that NaCl and KCl start to recrystallize within 5 min and K2SO4 within 15 min. The inactivation kinetics observed for the H1N1 influenza virus and Klebsiella pneumoniae matched the salt recrystallization well, which was identified as the main destabilizing mechanism. Additionally, the salt-coated filters were prepared with different methods (with and without a vacuum process), which led to salt coatings with different morphologies for diverse applications. Finally, the salt-coated filters caused a loss of pathogen viability independent of transmission mode (aerosols or droplets), against both DI water and artificial saliva suspensions. Overall, these findings increase our understanding of the salt-recrystallization-based technology to develop highly versatile antimicrobial filters.

Salt coatings functionalize inert membranes into high-performing filters against infectious respiratory diseases.

Respiratory protection is key in infection prevention of airborne diseases, as highlighted by the COVID-19 pandemic for instance. Conventional technologies have several drawbacks (i.e., cross-infection risk, filtration efficiency improvements limited by difficulty in breathing, and no safe reusability), which have yet to be addressed in a single device. Here, we report the development of a filter overcoming the major technical challenges of respiratory protective devices. Large-pore membranes, offering high breathability but low bacteria capture, were functionalized to have a uniform salt layer on the fibers. The salt-functionalized membranes achieved high filtration efficiency as opposed to the bare membrane, with differences of up to 48%, while maintaining high breathability (> 60% increase compared to commercial surgical masks even for the thickest salt filters tested). The salt-functionalized filters quickly killed Gram-positive and Gram-negative bacteria aerosols in vitro, with CFU reductions observed as early as within 5 min, and in vivo by causing structural damage due to salt recrystallization. The salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%). Combination of these properties in one filter will lead to the production of an effective device, comprehensibly mitigating infection transmission globally.

Protection induced by virus-like particle vaccine containing tandem repeat gene of respiratory syncytial virus G protein.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants, young children and the elderly. However, there is no licensed vaccine available against RSV infection. In this study, we generated virus-like particle (VLP) vaccine and investigated the vaccine efficacy in a mouse model. For VLP vaccines, tandem gene (1-780 bp) for V1 VLPs and tandem repeat gene (repeated 450-780 bp) for V5 VLPs were constructed in pFastBacTM vectors, respectively. Influenza matrix protein 1 (M1) was used as a core protein in the VLPs. Notably, upon challenge infection, significantly lower virus loads were measured in the lung of mice immunized with V1 or V5 VLPs compared to those of naïve mice and formalin-inactivated RSV immunized control mice. In particular, V5 VLPs immunization showed significantly lower virus titers than V1 VLPs immunization. Furthermore, V5 VLPs immunization elicited increased memory B cells responses in the spleen. These results indicated that V5 VLP vaccine containing tandem repeat gene protein provided better protection than V1 VLPs with significantly decreased inflammation in the lungs. Thus, V5 VLPs could be a potential vaccine candidate against RSV.

Respiratory Protection against Pandemic and Epidemic Diseases.

Respiratory protection against airborne pathogens is crucial for pandemic/epidemic preparedness in the context of personal protection, healthcare systems, and governance. We expect that the development of technologies that overcome the existing challenges in current respiratory protective devices will lead to a timely and effective response to the next outbreak.

Protection induced by virus-like particles containing Toxoplasma gondii microneme protein 8 against highly virulent RH strain of Toxoplasma gondii infection.

Toxoplasma gondii (T. gondii) microneme protein 8 (MIC8) represents a novel, functional distinct invasion factor. In this study, we generated virus-like particles (VLPs) targeting Toxoplasma gondii MIC8 for the first time, and investigated the protection against highly virulent RH strain of T. gondii in a mouse model. We found that VLP vaccination induced Toxoplasma gondii-specific IgG and IgG1 antibody responses in the sera. Upon challenge infection with RH strain of T. gondii tachyzoites, vaccinated mice showed a significant increase of both IgG antibodies in sera and IgA antibodies in feces compared to those before challenge, and a rapid expansion of both germinal center B cell (B220+, GL7+) and T cell (CD4+, CD8+) populations. Importantly, intranasally immunized mice showed higher neutralizing antibodies and displayed no proinflammatory cytokine IFN-γ in the spleen. Mice were completely protected from a lethal challenge infection with the highly virulent T. gondii (RH) showing no body weight loss (100% survival). Our study shows the effective protection against T. gondii infection provided by VLPs containing microneme protein 8 of T. gondii, thus indicating a potential T. gondii vaccine candidate.

Universal and reusable virus deactivation system for respiratory protection.

Aerosolized pathogens are a leading cause of respiratory infection and transmission. Currently used protective measures pose potential risk of primary/secondary infection and transmission. Here, we report the development of a universal, reusable virus deactivation system by functionalization of the main fibrous filtration unit of surgical mask with sodium chloride salt. The salt coating on the fiber surface dissolves upon exposure to virus aerosols and recrystallizes during drying, destroying the pathogens. When tested with tightly sealed sides, salt-coated filters showed remarkably higher filtration efficiency than conventional mask filtration layer, and 100% survival rate was observed in mice infected with virus penetrated through salt-coated filters. Viruses captured on salt-coated filters exhibited rapid infectivity loss compared to gradual decrease on bare filters. Salt-coated filters proved highly effective in deactivating influenza viruses regardless of subtypes and following storage in harsh environmental conditions. Our results can be applied in obtaining a broad-spectrum, airborne pathogen prevention device in preparation for epidemic and pandemic of respiratory diseases.

Microfabrication for Drug Delivery.

This review is devoted to discussing the application of microfabrication technologies to target challenges encountered in life processes by the development of drug delivery systems. Recently, microfabrication has been largely applied to solve health and pharmaceutical science issues. In particular, fabrication methods along with compatible materials have been successfully designed to produce multifunctional, highly effective drug delivery systems. Microfabrication offers unique tools that can tackle problems in this field, such as ease of mass production with high quality control and low cost, complexity of architecture design and a broad range of materials. Presented is an overview of silicon- and polymer-based fabrication methods that are key in the production of microfabricated drug delivery systems. Moreover, the efforts focused on studying the biocompatibility of materials used in microfabrication are analyzed. Finally, this review discusses representative ways microfabrication has been employed to develop systems delivering drugs through the transdermal and oral route, and to improve drug eluting implants. Additionally, microfabricated vaccine delivery systems are presented due to the great impact they can have in obtaining a cold chain-free vaccine, with long-term stability. Microfabrication will continue to offer new, alternative solutions for the development of smart, advanced drug delivery systems.