Photosensitizer‐Modified MnO2 Nanoparticles to Enhance Photodynamic Treatment of Abscesses and Boost Immune Protection for Treated Mice

The emergence of drug‐resistant bacteria and easy recurrence has been challenging in the clinical treatment of skin abscesses resulting from bacterial infections (e.g., by Staphylococcus aureus (S. aureus)). Herein, an antibacterial nanoagent capable of modulating the abscess microenvironment is designed to enhance photodynamic treatment of skin abscesses, and subsequently activate the immune system to effectively prevent abscess recurrence. In the system, manganese dioxide nanoparticles (MnO2 NPs) with high catalytic reactivity toward H2O2 are modified with photosensitizer chlorine e6 (Ce6) and coated with polyethylene glycol (PEG). The obtained Ce6@MnO2‐PEG NPs, by triggering the decomposition of lesion endogenous H2O2, are able to effectively relieve the hypoxic abscess microenvironment during S. aureus infection. The light‐triggered photodynamic bacterial killing effect could thus be remarkably enhanced, resulting in effective in vivo therapy of S. aureus‐induced skin abscesses. Interestingly, a notable pathogen‐specific immunological memory effect against future infection by the same species of bacteria is elicited after such treatment, owing to the release of bacterial antigens post photodynamic therapy (PDT) together with the adjuvant‐like function of manganese ions to activate the host immune system. This work thus presents a new type of photodynamic nanoagent particularly promising for highly effective light‐triggered abscess treatment and prevention of abscess recurrence. Chlorine e6‐manganese dioxide‐polyethylene glycol nanoparticles (Ce6@MnO2‐PEG NPs) can modulate the abscesses microenvironment by triggering the decomposition of lesion endogenous H2O2 to enhance photodynamic treatment of Staphylococcus aureus (S. aureus)‐induced skin abscesses. The release of bacterial antigens together with the adjuvant‐like function of manganese ions are capable of activating the host immune system, and subsequently eliciting notable pathogen‐specific immunological memory effect to effectively prevent abscess recurrence.