Hydroxyl Radical Generating Monovalent Copper Particles for Antimicrobial Application

Abstract

The antimicrobial properties of copper are well-known but maintaining a low oxidation state of Cu in particles is difficult. Herein, antimicrobial CuxP particles were synthesized through phosphorization of Cu(OH)2, to lock copper in its monovalent state (as Cu3P). We found that the phosphorization could be achieved at temperatures as low as 200°C, with stable surface presence of Cu(I) on the resulting CuxP particles. Cu(I) can act as a one-electron reducing agent for molecular oxygen, to generate the highly reactive hydroxyl radical. In this study, CuxP displayed antibacterial activities on the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, with minimum inhibitory concentrations of 32 mg/L for the highest temperature particles (350°C) on both model bacteria. The evident membrane damage is consistent with the intended hydroxyl radical bacterial targeting mechanism. Low-temperature CuxP, although exhibiting lower antibacterial efficacies than those of the higher temperature variant, still showed competitive growth inhibiting activities when compared to other reported antimicrobial copper-based particles. The present work showcases advancements in particle technology that can lead to the development of a more robust antimicrobial agent, presenting a potent additive for self-disinfection applications.