Antibacterial and antiviral activities of SiO2-Ag and ZrO2-Ag nanocomposite coatings deposited on polymeric air filters

Acute respiratory infections are the most common cause of acute illness globally and have a severe impact on human health and productivity. There is robust evidence of airborne transmission of many respiratory viruses via direct or indirect contact with droplets and aerosol produced by infected individuals, and this transmission route becomes crucial in crowded indoor spaces. Heating, ventilating and air conditioning (HVAC) systems filters can reduce the concentration of virus-carrying droplets, but HVAC systems able to directly inactivate bacteria and viruses are highly desirable to preserve safe indoor air. The aim of the present work was to assess the antibacterial and antiviral properties of silver nanoclusters/silica or zirconia composite coatings deposited onto polymeric air filters against Staphylococcus epidermidis, Staphylococcus aureus and a panel of representative members of human respiratory viruses, such as human coronavirus OC43 (HCoV-OC43), human rhinovirus A1 (HRV-A1), influenza virus type A (IFVA-H3N2) and adenovirus type -5 (AdV-5) according to standard protocols ISO. Results evidenced that both coatings showed a significant antimicrobial and antiviral activity at variable extent and a good cytocompatibility on all the examined cell lines, demonstrating a broad-spectrum action against selected bacteria and respiratory viruses.