Highly effective DPA-SCP sonosensitizers for biofilm removal in infected root canals via sonodynamic therapy†

In endodontic therapy, effective disinfection of root canals is crucial to prevent persistent infections, often caused by resilient biofilms such as those formed by Enterococcus faecalis. This study introduces a novel sonodynamic therapy (SDT) approach utilizing an aggregation-induced emission (AIE) sonosensitizer, DPA-SCP, activated by low-frequency ultrasound. The process involves four key steps: (1) application of low-frequency ultrasound to infected root canals, providing direct mechanical effects on biofilms; (2) activation of DPA-SCP by ultrasound energy, triggering the generation of reactive oxygen species (ROS); (3) ROS permeation through biofilm matrices, causing oxidative damage to bacterial cell walls and membranes, leading to cell death; and (4) synergistic biofilm eradication through ROS oxidation and ultrasound mechanical effects. In vitro experiments demonstrate that DPA-SCP, when combined with ultrasound, significantly reduces bacterial viability and biofilm integrity in infected root canals, showing comparable effectiveness to sodium hypochlorite, the current clinical standard. Moreover, DPA-SCP exhibits reduced cytotoxicity and minimal thermal effects, indicating its potential for safe clinical application. This multi-step, multi-mechanism approach not only improves the effectiveness of root canal treatment but also provides a new solution to overcome biofilm tolerance issues faced by conventional methods.