The role of ion dissolution in metal and metal oxide surface inactivation of SARS-CoV-2
Antiviral surface coatings are under development to prevent viral fomite transmission from high-traffic touch surfaces in public spaces. Coppers antiviral properties have been widely documented; but the antiviral mechanism of copper surfaces is not fully understood. We screened a series of metal and metal oxide surfaces for antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease (COVID-19). Copper and copper oxide surfaces exhibited superior anti-SARS-CoV-2 activity; however, level of antiviral activity was dependent upon the composition of the carrier solution used to deliver virus inoculum. We demonstrate that copper ions released into solution from test surfaces can mediate virus inactivation, indicating a copper ion dissolution-dependent antiviral mechanism. Level of antiviral activity is, however, not dependent on the amount of copper ions released into solution per se. Instead, our findings suggest that degree of virus inactivation is dependent upon copper ion complexation with other biomolecules (e.g., proteins/metabolites) in the virus carrier solution that compete with viral components. Although using tissue culture-derived virus inoculum is experimentally convenient to evaluate the antiviral activity of copper-derived test surfaces, we propose that the high organic content of tissue culture medium reduces the availability of "uncomplexed" copper ions to interact with the virus, negatively affecting virus inactivation and hence surface antiviral performance. We propose that laboratory antiviral surface testing should include virus delivered in a physiologically relevant carrier solution (saliva or nasal secretions when testing respiratory viruses) to accurately predict real-life surface antiviral performance when deployed in public spaces. ImportanceThe purpose of evaluating antiviral activity of test surfaces in the laboratory is to identify surfaces that will perform efficiently in preventing fomite transmission when deployed on high-traffic touch surfaces in public spaces. The conventional method in laboratory testing is to use tissue culture-derived virus inoculum, however this study demonstrates that antiviral performance of test copper-containing surfaces is dependent on the composition of the carrier solution in which the virus inoculum is delivered to test surfaces. Therefore, we recommend that laboratory surface testing should include virus delivered in a physiologically relevant carrier solution, to accurately predict real-life test surface performance in public spaces. Understanding the mechanism of virus inactivation is key to future rational design of improved antiviral surfaces. Here, we demonstrate that copper ions released from copper surfaces into small liquid droplets containing SARS-CoV-2, is a mechanism by which the virus that causes COVID-19 can be inactivated.