Abstract
Copper oxide is a representative inorganic antiviral material. However, the highly active Cu(2)O phase transforms gradually into CuO, which results in reduced antiviral activity. For this study, we aimed at developing a material with high antiviral activity based on CuO. To this end, La(2)CuO(4) and Y(2)Cu(2)O(5) were synthesized respectively by combining CuO with La(2)O(3) and Y(2)O(3). Their antiviral properties were investigated. For comparison, Al(2)CuO(4) and the simple oxides of each constituent element were also prepared and evaluated. The ternary oxides synthesized using citric acid combustion method and the solid-state reaction method were confirmed to be single-phase. Surface analysis revealed the presence of Cu(+) on La(2)CuO(4) and Y(2)Cu(2)O(5). The amount of ion release from these materials was found to be low. Antiviral activity tests were conducted against the nonenveloped bacteriophage Qβ and the enveloped bacteriophage Φ6, following ISO-standard evaluation methods. La(2)CuO(4) and Y(2)Cu(2)O(5) exhibited stronger antiviral activity against Qβ than either CuO, La(2)O(3), or Y(2)O(3). Detailed analyses suggested that the enhanced activity was attributable to strengthened electrostatic interactions and an improved ability to inactivate proteins. In contrast, La(2)O(3) and Y(2)O(3) showed relatively high antiviral activity against Φ6, primarily because of their strong affinity for phosphate groups. First-principles calculations indicate that (i) the surfaces of these ternary oxides containing Cu(2+) are cation-rich and (ii) the surface formal charge of copper is predominantly monovalent. These findings suggest that the unique surface states because of their crystal structures play a crucially important role in the antiviral performance of La(2)CuO(4) and Y(2)Cu(2)O(5). The antiviral activity of La(2)CuO(4) against Qβ exhibited high long-term stability, surpassing the reported performance of Cu(2)O. The present study is expected to provide promising new materials with improved antiviral activities compared to conventional CuO.