Effectiveness of the Nanosilver/TiO ₂ -Chitosan Antiviral Filter on the Removal of Viral Aerosols

Abstract

Background: The precaution of airborne transmission of viruses, such as influenza, SARS, MERS, and COVID-19, is essential for reducing infection. In this study, we applied a zero-valent nanosilver/titania-chitosan (nano-Ag 0 /TiO 2 -CS) filter bed, whose broad-spectrum antimicrobial efficacy has been proven previously, for the removal of viral aerosols to minimize the risk of airborne transmission. Methods: The photochemical deposition method was used to synthesize the nano-Ag 0 /TiO 2 -CS antiviral material. The surface morphology, elemental composition, and microstructure of the nano-Ag 0 /TiO 2 -CS were analyzed by a scanning electron microscopy/energy dispersive X-ray spectroscopy and a transmission electron microscopy, respectively. The MS2 bacteriophages were used as surrogate viral aerosols. The antiviral efficacy of nano-Ag 0 /TiO 2 -CS was evaluated by the MS2 plaque reduction assay (PRA) and filtration experiments. In the filtration experiments, the MS2 aerosols passed through the nano-Ag 0 /TiO 2 -CS filter, and the MS2 aerosol removal efficiency was evaluated by an optical particle counter and culture method. Results and Conclusions: In the MS2 PRA, 3 g of nano-Ag 0 /TiO 2 -CS inactivated 97% of MS2 bacteriophages in 20 mL liquid culture (2 ± 0.5 × 10 16 PFU/mL) within 2 hours. The removal efficiency of nano-Ag 0 /TiO 2 -CS filter (thickness: 6 cm) for MS2 aerosols reached up to 93%. Over 95% of MS2 bacteriophages on the surface of the nano-Ag 0 /TiO 2 -CS filter were inactivated within 20 minutes. The Wells–Riley model predicted that when the nano-Ag 0 /TiO 2 -CS filter was used in the ventilation system, airborne infection probability would reduce from 99% to 34.6%. The nano-Ag 0 /TiO 2 -CS filter could remain at 50% of its original antiviral efficiency after continuous operation for 1 week, indicating its feasibility for the control of the airborne transmission.

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