Research of Synergistic Photothermal Antibacterial Strategy Based on Polymeric Guanidine Derivative Grafted on Mesoporous Carbon Nanospheres

Bacterial infection is one of the major problems that seriously threaten people's life and health. In recent years, photothennal therapy (PTT), which uses photothermal conversion nanomaterials to convert optical energy into thermal energy for sterilization under specific wavelength laser irradiation, has aroused wide interest of researchers. Compared with traditional antibiotic therapy, the new anti-bacterial strategy photothennal therapy shows the excellent performance of controllable, minimally invasive and less bacterial resistance. However, monomodal PTT therapy is not ideal because it is often associated with side effects such as inflammatory reaction. Therefore, it is necessary to develop novel photothermal antibacterial system with high biocompatibility and safety to fight bacterial infection. Combined antibacterial strategy can effectively solve this problem. In this work, mesoporous carbon nanospheres (MCN) were prepared and oxidized by the mixed acid to obtain carboxyl-rich oxidized mesoporous carbon nanosphaes (OMCN) with high biocompatibility and photothermal properties. Then, OMCN-PHMB nano-antibacterial platform was obtained by grafting the antimicrobial agent poly(hexamethylene biguanide)hydrochloride (PHMB) onto the surface of OMCN with amide covalently. The photothermal properties of the system were evaluated and the results showed that the photothennal performance of OMCN had a good dependence on the concentration and power density of near-infrared light. Similar to the OMCN, the obtained OMCN-PHMB exhibited excellent performance of photothennal controllability and photothermal stability. In vivo and in vitro antibacterial experiments showed that the therapeutic effect of OMCN-PHMB under 808 nm laser irradiation was significantly better than that of other treatment groups under the single mode, which confirmed the excellent antibacterial effect of OMCN-PHMB combined with photothermal therapy. In addition, histological analysis showed that the nanoplatform had no significant toxicity to the major organs of mice, indicating OMCN-PHMB had a high biocompatibility. To sum up, the photothennal synergistic nano-antibacterial platform constructed in this study is expected to serve as a safe and controllable biomedical platform to combat various diseases caused by bacterial infection, providing a new antibacterial strategy for clinical treatment of bacterial infection diseases.