Graphene Quantum Dots Nanoantibiotic-Sensitized TiO 2-x Heterojunctions for Sonodynamic-Nanocatalytic Therapy of Multidrug-Resistant Bacterial Infections.

The exploration of sonodynamic therapy (SDT) as a possible replacement for antibiotics in antibacterial treatment by creating reactive oxygen species (ROS) has been suggested as a non-drug-resistant theranostic method. However, the low-efficiency ROS generation and complex tumor microenvironment (TME) which can deplete ROS and promote tumor growth would cause the compromised antibacterial efficacy of SDT. Herein, through an oxygen vacancy engineering strategy, we synthesize TiO 2-x microspheres with an abundance of Ti 3+ defects using a straightforward reductant co-assembly approach. The narrow bandgaps (2.0 eV) 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 heterojunction shows an increased production of ROS, which could be ascribed to the accelerated separation of electron-hole pairs, as well as the peroxidase-like catalytic activity mediated by Ti 3+ to produce •OH, and the depletion of excessive glutathione mediated by Ti 4+ . Moreover, the multiple-enzyme catalytic activities of TiO 2-x microspheres are amplified by the heterojunctions-accelerated carrier transfer. In addition, the well-confined GQDs can inhibit Topo I, displaying strong antibacterial activity and further enhancing the antibacterial activity of GQD/TiO 2-x -mediated synergetic SDT and nanocatalytic therapy (NCT). Collectively, the combination of GQD/TiO 2-x -mediated SDT/NCT with nanoantibiotics could result in a synergistic effect, allowing for multimodal antibacterial treatment that effectively promotes wound healing. This article is protected by copyright. All rights reserved.