Biofilm-Responsive Polymeric Nanoparticles with Self-Adaptive Deep Penetration for In Vivo Photothermal Treatment of Implant Infection

Biofilm can protect bacteria from immune attacks and antibiotic inhibition, and bacterial biofilm hosted in implanted materials and medical devices is a serious threat for modern medical system. Herein, we report biofilm-responsive caged guanidine nanoparticles (CGNs) to deeply penetrate and accumulate in bacterial biofilm, and then efficient photothermal eradication of bacterial biofilm is achieved upon NIR laser irradiation via the proof-of-concept formulation of photothermal agents in CGNs. In physiological conditions and blood circulation, CGNs are negatively charged by masking the positive charge of guanidine via covalent modification with acid-cleavable moieties, exhibiting high biocompatibility and minimal hemolysis. Whereas upon blood circulation and passive accumulation at infected implant sites, CGNs are self-adaptive in acidic biofilm to release the protective caging group and expose native guanidine moieties, which can promote nanoparticle deep biofilm penetration and bacteria adhesion as well as membrane fusion. After that, remarkable photothermal effect with a high photothermal conversion efficiency of ∼40.9% can eradicate implant biofilm upon NIR laser irradiation. It can efficiently treat S. aureus biofilm-infected implant catheters in vivo via only one single treatment in a mouse model, exhibiting ∼99.6% bacteria inhibition ratio. Apart from this proof-of-concept work, current guanidine-caged biofilm responsive polymeric nanoparticles are promising general vectors to treat biofilm and resistant pathogens in medicine and daily healthcare.