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

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.