Photocatalytic Treatments for Personal Protective Equipment: Experimental Microbiological Investigations and Perspectives for the Enhancement of Antimicrobial Activity by Micrometric TiO 2 .

The COVID-19 pandemic has led to countries enforcing the use of facial masks to prevent contagion. However, acquisition, reuse, and disposal of personal protective equipment (PPE) has generated problems, in regard to the safety of individuals and environmental sustainability. Effective strategies to reprocess and disinfect PPE are needed to improve the efficacy and durability of this equipment and to reduce waste load. Thus, the addition of photocatalytic materials to these materials, combined with light exposure at specific wavelengths, may represent promising solutions. To this aim, we prepared a series of masks by depositing micrometer-sized TiO2 on the external surfaces; the masks were then contaminated with droplets of bacteria suspensions and the coatings were activated by light radiation at different wavelengths. A significant reduction in the microbial load (over 90%, p < 0.01) was observed using both Gram negative (E. coli) and Gram positive (S. aureus) bacteria within 15 min of irradiation, with UV or visible light, including sunlight or artificial sources. Our results support the need for further investigations on self-disinfecting masks and other disposable PPE, which could positively impact (i) the safety of operators/workers, and (ii) environmental sustainability in different occupational or recreational settings.