Antitumor effects of Escherichia coli-derived outer membrane vesicles loaded with ferrous sulfide on oral squamous cell carcinoma

Objective To evaluate the therapeutic efficacy of OMV@FeS against oral squamous cell carcinoma(OSCC). Methods Escherichia coli-derived outer membrane vesicle (OMV) was extracted using ultracentrifugation and co-precipitated with FeS to form OMV@FeS. The morphology, average particle size, Zeta potential, and elemental composition of OMV@FeS were characterized. Photothermal performance under 808 nm laser irradiation was assessed. Intracellular reactive oxygen species(ROS) levels and mitochondrial membrane potential changes were detected using DCFH-DA and JC-1 probes respectively on squamous cell carcinoma(SCC-7) cells. The synergistic cytotoxicity of OMV@FeS combined with laser irradiation was evaluated through CCK-8 and Calcein-AM/PI dual staining, respectively. Flow cytometry analysis was employed to evaluate the induction of tumor-associated macrophage polarization and maturation of undifferentiated dendritic cells. A subcutaneous xenograft model of SCC-7 was developed to systematically evaluate the antitumor efficacy and biosafety of OMV@FeS. Results Transmission electron microscopy(TEM) analysis confirmed that FeS was uniformly distributed within OMV vesicles to form OMV@FeS. Under near-infrared laser (808 nm) irradiation, the temperature of the OMV@FeS system (>100 μg/mL) could exceed 55 ℃, meeting the tumor ablation temperature required for photothermal therapy. The photothermal conversion rate was 58.7%, demonstrating excellent photothermal performance and stability. When combined with OMV@FeS under laser irradiation, significant ROS generation and a marked decrease in JC-1 fluorescence-labeled mitochondrial membrane potential were observed within SCC-7 cells. Calcein-AM/PI dual staining and CCK-8 assays revealed that the combination of OMV@FeS with a near-infrared laser exhibited significant synergistic cytotoxic effects against SCC-7 cells. Flow cytometry analysis demonstrated that OMV@FeS effectively induced the polarization of M2 macrophages toward the M1 phenotype. Furthermore, flow cytometry analysis of CD80 and CD86 demonstrated that OMV@FeS combined with near-infrared laser irradiation significantly promoted the maturation of dendritic cells. The tumor-inhibiting effect of OMV@FeS under laser intervention was highly significant in SCC-7 tumor-bearing mice, as evidenced by a continuous reduction in tumor volume. HE staining demonstrated significant apoptotic or necrotic features in tumor cells, further validating the efficacy of this combined therapy strategy in vivo. Conclusion OMV@FeS exhibits synergistic effects of photothermal therapy, photodynamic therapy and immunotherapy under near-infrared laser irradiation, realizing combined enhancement of physical therapy and biological immunotherapy, thereby exerting a positive therapeutic effect on OSCC.