Ozone-delivering nanocomposite hydrogel for acute Staphylococcus aureus osteomyelitis treatment via neutrophil regulation

Treatment of acute osteomyelitis (OM) poses a significant challenge because of the difficulty in removing bacteria and the aberrant innate immune responses at the infection site. Topical ozone therapy has demonstrated favorable outcomes in treating OM, but its high reactivity and short half-life severely limit its clinical application. To address this issue, a suitable ozone delivery system that can promote the therapeutic effects of topical ozone therapy in OM is needed. In this study, we developed ozone-loaded fluorinated hyaluronic acid nanoparticles embedded in a thermoresponsive hydroxypropyl chitin (HPCH) hydrogel (Ozone@Gel) for treating acute OM. The ozone-delivering nanocomposite hydrogel could release ozone continuously and stably at the injection site for over 15 days. The ozone loaded in this ozone-delivering nanocomposite hydrogel was about 100 mg/L. In vitro antibacterial experiments demonstrated that the Ozone@Gel effectively attenuated Staphylococcus aureus proliferation and reduced biofilm formation by inhibiting the expression of bacterial polysaccharide-related genes (agr, atlE, aap, icaA, and icaBC). Further, animal experiments showed that Ozone@Gel effectively reduced bacterial load at the site of infection by enhancing neutrophil antimicrobial activity, thereby alleviating the progression of acute OM. Thus, this novel therapeutic strategy based on topical ozone therapy is a promising and feasible intervention for treating acute S. aureus OM.