Acid‐Triggered, Enzyme‐Enabled EPS‐Degrading Nanoplatform With Enhanced In Situ Retention for Intravenous Biofilm Therapy

ABSTRACT Bacterial biofilms present a major challenge to antibacterial therapy due to their dense extracellular polymeric substance (EPS) matrix, which limits nanoparticle penetration and reduces drug efficacy. Here, we report a pH‐responsive, surface charge‐adaptive multifunctional nanosystem (DA‐L@DTTB/Bro) for efficient in vivo treatment of biofilm‐associated infections. The nanosystem integrates pH‐triggered charge adaptation, in situ self‐aggregation, photothermal responsiveness, enzymatic EPS degradation, and NIR‐II imaging. Cationic phospholipid AGPDP, together with cholesterol and thermosensitive DPPC, self‐assembled into liposomes encapsulating bromelain in the hydrophilic core and an NIR‐II‐emissive photothermal agent (DTTB) in the hydrophobic layer. Surface modification with DA‐functionalized chitosan (CS‐DA) generates negatively charged nanoparticles for prolonged circulation. At acidic infection sites, DA hydrolysis restores the cationic surface, enhancing biofilm penetration, while residual CS‐DA induces self‐aggregation to improve retention. NIR irradiation triggers DTTB‐mediated hyperthermia, directly killing bacteria and disassembling liposomes to release bromelain, which degrades EPSs and facilitates biofilm dispersion. The nanosystem eradicates methicillin‐resistant Staphylococcus aureus biofilms in vitro with 99.99% efficiency, enables high‐contrast NIR‐II imaging, persists at abscess sites in vivo, and accelerates wound healing. Furthermore, it demonstrates effective therapeutic activity against biofilm‐associated infections in deep pulmonary tissues. This study presents a versatile intravenous strategy for targeted, synergistic therapy against biofilm‐associated infections in vivo.