Stable and biocompatible multivalent polymer-grafted gold nanorods for enhanced photothermal antibacterial therapy

Near-infrared laser-activated gold nanorods (AuNRs) with excellent photothermal property and tunable surface functionalization are considered as an ideal platform for biomedical applications. However, bare AuNRs have cytotoxicity against normal cells and are prone to agglomeration during laser irradiation. Herein, multivalent polymer-functionalized AuNRs (AuNRs@pDMAEMA-C₄) was constructed as a highly stable and biocompatible photothermal agent for enhanced antibacterial therapy. The functionalized polymer was synthetized via the reversible addition-fragmentation chain transfer polymerization and subsequently quaternized. Moreover, positively charged AuNRs@pDMAEMA-C₄ can easily capture the bacterial surface via electrostatic interactions. The integration of photothermal therapy of AuNRs and chemotherapy of functionalized polymer can achieve enhanced antibacterial effects. Under 808 nm laser irradiation, AuNRs@pDMAEMA-C₄ possessed excellent photothermal conversion capability and can kill gram-positive and gram-negative bacteria. Study of the antibacterial mechanism indicated that the antibacterial action of the prepared photothermal antibacterial agent can cause serious damage of the bacterial outer membranes, result in cytoplasm leakage and bacterial death. The nanocomposites combining with near-infrared laser irradiation can facilitate rapid healing of bacteria-infected wound by rat model of wound infection and histological analysis of the wound tissues. These results suggest that the surface functionalization can be used as potential strategy to fabricate light-activated therapeutic agent for biomedical applications.