An NIR-Responsive Theranostic Gutta-Percha for Bacterial Sensing and Photothermal Disinfection during Root Canal Treatment

Abstract Root canal treatment (RCT) is the standard endodontic procedure for eliminating infection and preserving natural teeth. However, treatment failure can occur when residual bacteria persist within complex root canal anatomies, as current irrigation protocols do not provide direct confirmation of bacterial presence prior to obturation. Herein, we present SteriGP, an engineered Gutta-Percha (GP)-based proof-of-concept theranostic platform that integrates bacterial detection with localized photothermal disinfection during root canal treatment. SteriGP employs a ferricyanide-mediated bioreaction in which respiration-driven electron transfer from metabolically active bacteria promotes the in situ formation of Prussian blue (PB), providing a visible indicator of bacterial activity. The generated PB exhibits strong near-infrared (NIR) absorption and, upon 808 nm laser irradiation, produces localized hyperthermia for targeted photothermal inactivation of residual bacteria. SteriGP demonstrated concentration-dependent PB formation, photothermal heating, and antibacterial activity against both planktonic and biofilm models of representative Gram-negative (Escherichia coli) and Gram-positive (methicillin-resistant Staphylococcus aureus) bacteria. Furthermore, evaluation in an E. coli biofilm-based resin root canal model demonstrated visible bacterial detection within the canal and effective reduction of bacterial regrowth following NIR irradiation. Collectively, these findings establish the feasibility of integrating bacterial-responsive sensing and localized photothermal therapy into a Gutta-Percha platform for endodontic applications. While additional studies evaluating cytocompatibility, clinically relevant oral pathogens, natural tooth models, and in vivo performance are required, this work provides a foundation for the future development of theranostic biomaterials for precision-guided root canal treatment.