Fabrication of NIR-II-Responsive Polydextran Aldehyde/Gelatin/Gold Nanoparticle-Decorated Graphene Oxide Nanocomposite Hydrogels for Antibacterial Applications

Near-infrared (NIR)-responsive nanocomposite hydrogels are increasingly utilized in biomedical applications due to their ability to undergo remote-controlled deformation and the deep tissue penetration of NIR light. However, applying high-power lasers may cause skin injuries at the irradiation sites, raising safety concerns for clinical use. Also, the lack of dynamic features (such as self-healing) and processing capability (such as injectability) of the NIR-responsive nanocomposite hydrogels restricts their advanced applications. Here, we enhanced the photothermal efficiency of graphene oxide (GO) by attaching gold nanoparticles (AuNPs), creating a AuNP-decorated GO (GOAu). This GOAu was integrated into a thermoresponsive imine cross-linked hydrogel network made of polydextran aldehyde (PDA) and gelatin (Gel), resulting in PDA/Gel/GOAu nanocomposite hydrogels. The PDA/Gel/GOAu nanocomposite hydrogels were constructed through multiple cross-linking chemistries, including noncovalent chemistry (i.e., coordination, electrostatic interaction, and hydrogen bond) and dynamic covalent chemistry (i.e., imine bond). The structures and properties of the PDA/Gel/GOAu nanocomposite hydrogels were comprehensively investigated in comparison with the PDA/Gel hydrogels and PDA/Gel/GO nanocomposite hydrogels. Adding GOAu to the PDA/Gel network reduced the gelation time of hydrogel formation and improved the rheological and mechanical properties of the PDA/Gel network. The PDA/Gel/GOAu hydrogels exhibited a dose-dependent thermal response to NIR-II light (1064 nm), with the PDA/Gel/GOAu hydrogel containing 4 wt % GOAu achieving the highest temperature among the other hydrogels. The enhanced photothermal properties of the PDA/Gel/GOAu hydrogels were also applied in antibacterial applications based on their capability to perform thermal-induced bactericidal activity and controlled drug release under NIR-II light. Also, with their dynamic properties (i.e., NIR responsiveness, self-healing, and injectability), PDA/Gel/GOAu nanocomposite hydrogels are promising biomaterials for various applications.