NIR-Activated Polydopamine Nanoparticles for Enterococcus faecalis Biofilm Eradication in Root Canal Disinfection

Persistent bacterial infection remains the primary cause of root canal treatment failure, posing a significant challenge in endodontics. Enterococcus faecalis, with its ability to form biofilms and resist conventional disinfectants, is one of the most commonly isolated species in failed cases. Herein, we developed a novel polydopamine (PDA) nanoparticle-based phototherapy system activated by 808 nm near-infrared (NIR) light for enhanced root canal disinfection. The PDA + NIR group exhibited a significantly superior antibacterial effect compared to 2.5% NaOCl, achieving a bactericidal rate of 97.87%. SEM and TEM observations revealed that PDA + NIR treatment caused complete bacterial cell disintegration and ultrastructural destruction, whereas 2.5% NaOCl only induced partial surface damage. Furthermore, PDA + NIR effectively eradicated mature E. faecalis biofilms in simulated root canal models. These findings demonstrate that PDA-mediated NIR phototherapy possesses powerful bactericidal and antibiofilm capabilities. This nanotechnology-based approach may offer a promising alternative strategy for clinical root canal disinfection.