Silver Nitrate and Bioactive Glass Containing Chitosan Coatings: Comparison of Antimicrobial and Antiviral Properties

Pathogenic air and water contaminations present major health issues nowadays. Filter-based protective devices have been commonly utilized to capture airborne or waterborne microorganisms and viruses in order to reduce or inhibit the transmission of infectious diseases. Some approaches to extend the functionality of filtering devices and to further enhance their capability to inactive pathogens include the application of antimicrobial coatings on the filter surface. In this regard, the current work aims to develop innovative coatings with antiviral and antibacterial properties composed of a chitosan matrix incorporating bioactive glass (BG) nanoparticles or silver nitrate (AgNO₃) on metallic filters by using electrophoretic deposition. The so-produced chitosan/BG- and chitosan/AgNO₃-coated filters were characterized in terms of their morphology, chemical composition, filtering capability, antibacterial properties against Staphylococcus aureus, and antiviral activity against coronavirus OC43, rhinovirus, adenovirus, and influenza virus. The results confirmed that chitosan/AgNO₃ and chitosan/BG coatings exhibited no blockage of the filter pores. The bubble point values for both coating types were similar to the measurements of uncoated filters, suggesting intact filtration capability after the application of the coatings. The antibacterial assay showed the antibacterial activity of >99% for both chitosan/AgNO₃ and chitosan/BG coatings against S. aureus. Finally, chitosan/AgNO₃-coated filters showed antiviral activity against three out of the four tested viruses (HCoV-OC43, HRV-A1, and IFV-AH3N2) and exerted a partial antiviral action against AdV-5. On the other hand, chitosan/BG-coated filters were active against all tested respiratory viruses. The outcomes of this study evidenced that the developed multimaterial coatings could serve as a suitable platform to produce antimicrobial filtering systems for a broad-spectrum application.