Oxygen-Carrying Acid-Responsive Cu/ZIF-8 for Photodynamic Antibacterial Therapy against Cariogenic Streptococcus mutans Infection

Caries as a result of acid demineralization is the most common oral microbial infection disease. Due to the small and complex intraoral operating space, it is challenging to completely remove Streptococcus mutans (S. mutans) and other cariogenic bacteria. As an intelligent acid-responsive photosensitive nanomaterial, O2-Cu/ZIF-8@Ce6/ZIF-8@HA (OCZCH) was chosen to adapt the anaerobic and acidic microenvironment to inactivate S. mutans. In this work, OCZCH not only has a regular nanomorphology under the SEM and TEM images but also has an intelligent acid responsiveness as evidenced by the release of Ce6 and oxygen. When excited by near-infrared light at 650 nm, Ce6 released reactive oxygen species (ROS) that act synergistically with internal oxygen to significantly enhance the antimicrobial therapeutic effect of photodynamic therapy (PDT). In vitro, antimicrobial experiments showed that OCZCH could achieve an impressive sterilization effect against S. mutans and the biofilm. Notably, the acid-producing ability of the bacteria was also significantly inhibited. Considering its oxygen-carrying photosensitizing properties, excellent responsiveness to acidic environments, and antimicrobial capacity under anaerobic conditions, OCZCH is considered an innovative candidate for clinical application in treating dental caries.