Polypyrrole-Modified Triple-Responsive Hydrogel Dressing Based on Bacterial Cellulose and Quaternary Ammonium Chitosan and Its Synergistic Antibacterial Mechanism

Smart antibacterial materials are gaining attention for their potential in controlled drug release and efficient treatment. This study constructed a composite hydrogel based on oxidized bacterial cellulose (OBC) and quaternary ammonium chitosan (QAC). This hydrogel was loaded with the natural antibacterial drug berberine (Ber) and utilized the abundant functional groups (such as amino and carboxyl groups) on OBC and QAC to achieve pH responsiveness, achieving on-demand drug release in the alkaline microenvironment of simulated chronic wounds. By further in situ polymerization of polypyrrole (PPy) on the hydrogel surface, the composite hydrogel (OBC/QAC/Ber/PPy) was endowed with excellent photothermal and electrothermal conversion properties. Systematic characterization showed that the OBC/QAC/Ber/PPY hydrogel had a high compressive strength of 135.6 kPa, self-healing ability, excellent biocompatibility, and significant antimicrobial activity. Notably, the introduction of the PPy layer also synergistically enhanced the inherent antibacterial properties of QAC and Ber through thermal effects; under photothermal stimulation, inhibition zones against <i>E. coli</i> and <i>S. aureus</i> reached 8.0 and 6.2 mm, respectively. Mouse wound models showed that the OBC/QAC/Ber/PPy composite hydrogel significantly accelerated wound healing, with a 27.03% improvement in the wound healing rate after 15 days compared to pure BC films. In summary, the OBC/QAC/Ber/PPy composite hydrogel, which integrates pH responsiveness, photoelectric thermal synergistic therapy, and multiple antibacterial mechanisms, provides a promising strategy for developing next-generation smart wound dressings and addressing bacterial resistance challenges.