Thermo-sensitive antibacterial applications of smart responsive hydrogels loaded with conjugated molecular materials

Bacterial infections have seriously threatened global health. The continuous activity of conventional antibacterial agents can disrupt the local microenvironment and accelerate bacterial resistance, ultimately compromising their long-term antibacterial efficacy, highlighting the need for on-demand antibacterial strategies. This study presents a smart, temperature-responsive and light-controlled antibacterial polysaccharide hydrogel model based on hyaluronic acid (HA), gelatin (Gel) and the loaded conjugated oligomer or polymer (OPV or PBF). By modulating the conditions, the hydrogel (HA-Gel@OPV or HA-Gel@PBF) is endowed with temperature-responsive properties, specifically transitioning from a gel to a sol as the temperature increases. The hydrogel effectively encapsulates conjugated oligomers and polymers with photodynamic antibacterial activity and, more importantly, imparts superior temperature-responsive release and light-controlled antibacterial capabilities. At room temperature and below, the hydrogel maintains a stable gel state, where the conjugated materials are confined and remain inactive. Upon reaching body temperature and above, the hydrogel transitions to a sol state, facilitating the effective release of the conjugated materials and activating their antibacterial effects under light exposure. Notably, the hydrogels loaded with 3 µM of OPV or 10 µM of PBF demonstrate an antibacterial efficacy of over 98% against S. aureus. This work introduces a novel approach for the application of responsive hydrogels and expands the potential for the use of photoactive conjugated materials for clinical applications, highlighting their engineering application potential.