Transparent Silver Oxide Coating That Inactivates SARS-CoV-2 and Kills Bacteria

The COVID-19 pandemic has caused nearly five million deaths worldwide by October 2021. While the main transmission route of SARS-CoV-2, the virus responsible for this disease, is through the inhalation of contaminated respiratory droplets, the transmission also occurs through the contaminated objects. Such objects are called fomites and this mode of transmission has proven to be responsible for 25% of COVID-19 cases and also accountable for the spread of a number of pathogenic bacteria such as <i>Pseudomonas aeruginosa</i> (<i>P. aeruginosa</i>), <i>Staphylococcus aureus</i> (<i>S. aureus</i>) and MRSA. Antimicrobial coatings and surfaces can minimize fomite transmission by inactivating the virus or killing the bacteria landed on the surface, thereby reducing the time period in which an object remains contaminated. In this study, we designed and fabricated silver oxide surface coatings that efficiently reduce the load of viable microbes on coated surfaces. First, we synthesized Ag₂O micro particles and then we employed a variant of Stöber sol-gel process to bound the particles onto glass substrate. Three different coated surfaces were fabricated by changing particle and binder loadings. The antimicrobial properties of the coatings were then assessed against SARS-CoV-2 and bacteria using Median Tissue Culture Infectious Dose (TCID50) and Colony Forming Units (CFU) methods respectively. Results indicated excellent antimicrobial activity, where the titer of SARS-CoV-2 was reduced by 99.8% and the number of the above mentioned bacteria was reduced by &gt;99.9% on average after one hour on coated surfaces. Experiments in the absence of light showed that the antimicrobial properties of the coatings are not affected by light and retained in dark. Results demonstrated that the coatings are completely potent after multiple exposures of bacteria to the coating, or after abrasion. Another important property of the coating is that it is transparent, and that the transmission of light is approximately uniform across the visible spectrum. The combination of strong antimicrobial activity and transparency means that this coating can be applied to cell phone touch screens, checkout facilities and other frequently touched objects in public places to limit the transmission of microbes.