Antiviral effects of copper and copper alloy and the underlying mechanisms in severe acute respiratory syndrome coronavirus 2

Abstract

Copper has antibacterial and antiviral properties and is effective against severe acute respiratory syndrome coronavirus 2; however, the detailed mechanism of virus inactivation remains unclear. Here, purified viruses were used to clarify the viral inactivation effect and to identify viral inactivation factors and damaged viral structures. When the virus is in contact with copper, the infectivity titer decreased by approximately 5-log₁₀ in 30 min; however, in contact with a copper alloy C22000 (90 % Cu, 10 % Zn) surface, it decreased by > 6-log₁₀ in only 10 min. To investigate its inactivation mechanism, RNA copy number of infectious viral particles was quantified using RNase treatment, oligo(dT)-based reverse transcriptase, and droplet digital polymerase chain reaction. Contact with copper and copper alloys causes fragmentation of the viral RNA over time; however, degradation is slow. The amount of spike protein on the viral membrane measured by enzyme-linked immunosorbent assay was only slightly reduced; however, C22000 was capable of degrading more than copper. The virus also reacted on the plates with chelators of copper ions and scavengers of reactive oxygen species as inhibitors of copper and copper alloy inactivating factors. The synergistic effects of copper ions, Cu(I) and Cu(II), and superoxide were found to be the significant inactivating factors of the virus. Furthermore, copper and copper alloy-coated textiles were prepared, and the inactivation efficacy was evaluated. Surprisingly, textiles coated with C21000 (Cu 95 %, Zn 5 %) showed the highest antiviral activity, decreasing by >6-log₁₀ to below the detection limit after only 2 min of contact.