Abstract: PURPOSE: This study aims to develop an active F.nucleatum (Fn) bio-delivery system (BiS/CeO₂@Fn) loaded with composite nanorods and to characterize its properties. The antitumor efficacy of BiS/CeO₂@Fn against oral squamous cell carcinoma (OSCC) was preliminarily evaluated. METHODS: Bismuth sulfide/cerium oxide (BiS/CeO₂) composite nanorods were synthesized using a hydrothermal method, and BiS/CeO₂@Fn was prepared via electrostatic adsorption. The micromorphology, average particle size, and Zeta potential were characterized using transmission electron microscopy (TEM) and a laser nanoparticle size/potentiometer. The photothermal performance of BiS/CeO₂@Fn under 808 nm laser irradiation was recorded using a near-infrared thermal imaging camera. The catalase (CAT) and peroxidase (POD) activities of BiS/CeO₂@Fn were evaluated by monitoring the production of O₂ and hydroxyl radicals (·OH). Intracellular reactive oxygen species (ROS) and O₂ generation was assessed using a DCFH-DA probe and an oxygen fluorescent probe, respectively. The synergistic cytotoxicity effect of BiS/CeO₂@Fn on CAL27 cells was investigated through live/dead cell staining and cell proliferation assays. Immunogenic cell death (ICD) effects were examined by monitoring intracellular ATP levels and immunofluorescence staining for calreticulin (CRT) and high mobility group protein B1 (HMGB1). Results: The synthesized BiS/CeO₂ nanorods exhibited a mean diameter of approximately 303.21 nm and a Zeta potential of (4.70±1.30) mV. TEM image revealed distinct adherence of nanoparticles around the bacteria following incubation with Fn, indicating the successful fabrication of BiS/CeO₂@Fn. This composite demonstrated excellent photothermal conversion efficiency and significant CAT and POD catalytic activities. Furthermore, BiS/CeO₂@Fn not only effectively alleviated tumor hypoxia, but also prompted ROS generation, suppressed tumor cell viability, and upregulated the expression of ICD hallmark molecules. CONCLUSIONS: The BiS/CeO₂@Fn live bacterial bio-delivery system demonstrates a synergistic cytotoxicity against CAL27 tumor cells through photothermal ablation, chemical dynamics therapy and immunotherapy. This multifunctional delivery system demonstrates significant therapeutic potential for treatment of OSCC.

Key words: Oral squamous cell carcinoma, F.nucleatum, Photothermal therapy, Chemodynamic therapy, Immunotherapy