Graphene Quantum Dots Nanoantibiotic‐Sensitized TiO2−x Heterojunctions for Sonodynamic‐Nanocatalytic Therapy of Multidrug‐Resistant Bacterial Infections

Abstract The exploration of sonodynamic therapy (SDT) as a possible replacement for antibiotics by creating reactive oxygen species (ROS) is suggested as a non‐drug‐resistant theranostic method. However, the low‐efficiency ROS generation and complex tumor microenvironment which can deplete ROS and promote tumor growth will cause the compromised antibacterial efficacy of SDT. Herein, through an oxygen vacancy engineering strategy, TiO 2− x microspheres with an abundance of Ti 3+ are synthesized using a straightforward reductant co‐assembly approach. The narrow bandgaps and Ti 3+ /Ti 4+ ‐mediated multiple‐enzyme catalytic activities of the obtained TiO 2− x microspheres make them suitable for use as sonosensitizers and nanozymes. When graphene quantum dot (GQD) nanoantibiotics are deposited on TiO 2− x microspheres, the resulting GQD/TiO 2− x shows an increased production of ROS, which can be ascribed to the accelerated separation of electron–hole pairs, as well as the peroxidase‐like catalytic activity mediated by Ti 3+ , and the depletion of glutathione mediated by Ti 4+ . Moreover, the catalytic activities of TiO 2− x microspheres are amplified by the heterojunctions‐accelerated carrier transfer. In addition, GQDs can inhibit Topo I, displaying strong antibacterial activity and further enhancing the antibacterial activity. Collectively, the combination of GQD/TiO 2− x ‐mediated SDT/NCT with nanoantibiotics can result in a synergistic effect, allowing for multimodal antibacterial treatment that effectively promotes wound healing.