Antimicrobial Fe₂O₃-CuO-P₂O₅ glasses

Glasses with high antimicrobial efficacy were developed in the Fe₂O₃-CuO-P₂O₅ ternary system to mitigate fomite-mediated transmission of infectious diseases in high-risk settings such as hospitals, daycares, and nursing homes. Binary CuO-P₂O₅ glasses were not durable enough for use as high touch point articles, so Fe₂O₃ was added to the compositions to increase the chemical durability. The amount of Cu leachate decreased by at least 3 orders of magnitude when Fe₂O₃ was increased from 0 to 13.1 mol%. At the highest Fe₂O₃ contents and corresponding highest durability, the glass was no longer able to pass a test of antimicrobial efficacy with < 3 log kill compared to > 5 log kill for all other compositions. Ab-initio molecular dynamics simulations showed increasing bridging oxygen species at the expense of non-bridging oxygen species with the increase in Fe₂O₃ content, showing that the glasses exhibited increased chemical durability because they were more interconnected and structurally bound. Experimental results with glasses at fixed CuO and decreasing Fe₂O₃ confirmed that Fe₂O₃ content (not CuO) controlled the Cu release rate and, thus, the antimicrobial efficacy of the glasses. The significance of the oxidation state of the leached Cu was overwhelmed by the importance of the amount of Cu leachate.