Functionalized zinc oxide microparticles for improving the antimicrobial effects of skin-care products and wound-care medicines

ZnO is an important component in skin-protection products and wound-care medicines. However, ZnO's antibacterial activity is moderate. We developed two types of ZnO microparticles loading with phthalocyanine-type photosensitizers (ZnO/PSs) introducing the photodynamic effects. These photosensitive ZnO microparticles exhibited long-term while moderate antimicrobial effects by continuously releasing Zn2+ ions. The antimicrobial efficacies were remarkably enhanced by triggering the photodynamic antimicrobial effects. Compared to the sole ZnO which showed non-measurable antimicrobial activity at a concentration of 10 mg/L, both ZnO/PSs demonstrated antimicrobial rates ranged 99%–99.99% against Escherichia coli, normal and drug-resistant Staphylococcus aureus. In a dorsal wound infection mouse model, treatment with ZnO/PSs significantly accelerated the wound recovery rates. ZnO/PSs promoted wound healing by a dual effect: 1) the release of Zn2+ ions from ZnO facilitating tissue remodeling; 2) the photodynamic effect efficiently eliminates pathogens avoiding infection. Notably, ZnO/PSs inherited the high biosafety of ZnO without causing noticeable toxicity against erythrocyte and endothelial cells. This study not only provides a highly safe and efficient antimicrobial ZnO material for skin cares and wound modulations, but also proposes a strategy to functionalize ZnO materials.