Trade-offs in Dual-Layer Surface Disinfection: Ozone Treatment on Surface-Immobilized Quaternary Ammonium Coatings

Abstract

The COVID-19 pandemic has highlighted the importance of effective surface disinfection strategies, as contaminated droplets settling on high-touch surfaces remain a major source of pathogen transmission. While antimicrobial surface coatings such as silane-functionalized quaternary ammonium compounds (silane-quats) offer durable, contact-based protection against oncoming pathogens, their mode of action is inherently slow. Dual-action/hybrid approaches combining fast-acting oxidizing agents, such as ozone, with these antimicrobial coatings are often proposed. Previous reports have shown that ozone can act synergistically with quaternary ammonium surfactants in solution, improving short-term microbial inactivation. However, little is known about the effect of ozone on surface-bound silane-quats, where direct chemical interactions may alter long-term performance. In this study, we examine the impact of ozone exposure on silane-quat-coated surfaces using bacteria-laden droplets as a model contamination scenario. We observe that ozone treatment reduces droplet spreading, indicative of lowered surface energy, and leads to diminished antimicrobial efficacy, as shown by reduced bacterial inactivation compared to untreated coatings. These results suggest that, beyond altering wettability, ozone may also compromise the functional integrity of the silane-quat layer, consistent with oxidative modification of quaternary ammonium groups. Our findings highlight an important caveat for layered disinfection strategies: while ozone provides rapid, on-demand microbial kill, it may simultaneously undermine the long-term effectiveness of silane-quat antimicrobial coatings. This underscores the need to evaluate chemical compatibility when designing hybrid approaches for reliable infection control in high-touch environments.