pH-Activated Scallop-Type Nanoenzymes for Oxidative Stress Amplification and Photothermal Enhancement of Antibacterial and Antibiofilm Effect

Ferric phosphate (FePOs) nanoenzymes can express peroxidase (POD) activity under the dual stimulation of an acidic environment and high H 2 O 2 concentrations. In living organisms, this generates reactive oxygen species (ROS) in sites of lesion infection, and thus FePOs nanoenzymes can act as antimicrobial agents. Here, CeO 2 and ZnO 2 were immobilized in a scallop-type FePOs nanoenzyme material loaded with a photosensitizer, indocyanine green, to synthesize a multifunctional cascade nanoparticle system (FePOs–CeO 2 –ZnO 2 –ICG, FCZI NPs). H 2 O 2 concentrations could be adjusted through the ZnO 2 self-activation response to the slightly acidic environment in biofilms, further promoting the release of ROS from the POD-like reaction of FePOs, achieving amplification of oxidative stress, DNA and cell membrane damage, and exploiting the photodynamic/photothermal effects of indocyanine green to enhance the antibiofilm effects. CeO 2 can remove redundant ROS by switching from Ce 4+ to Ce 3+ valence, enhancing its ability to fight chronic inflammation and oxidative stress and thus promoting the regeneration of tissues around infection. By maintaining the redox balance of normal cells, increasing ROS at the infection site, eliminating redundant ROS, and protecting normal tissues from damage, the synthesized system maximizes the elimination of biofilms and treatment at the infection site. Therefore, this work may pave the way for the application of biocompatible nanoenzymes.