An engineered bacteria-chitosan hybrid robot for lactate depletion and synergistic STING activation to potentiate bladder cancer immunotherapy

The treatment of bladder cancer faces multiple challenges, including poor tumor tissue penetration, low drug delivery efficiency, and an immunosuppressive microenvironment. To overcome these bottlenecks, this study constructed a novel bacteria-chitosan hybrid robot. The system utilizes electrostatic interactions to combine engineered Escherichia coli expressing lactate oxidase with positively charged chitosan nanoparticles, with the latter co-loaded with a chemotherapeutic drug Doxorubicin (DOX) and the DNA repair inhibitor olaparib. Following intravesical instillation, the engineered bacteria actively target and penetrate tumor tissues, significantly enhancing the accumulation and retention of nanomedicine at the lesion site. The bacteria colonizing the tumor continuously metabolize local lactate, which not only enhances chemosensitivity but also effectively alleviates tumor immunosuppression. Importantly, lactate consumption itself directly promotes the activation of the STING pathway. Simultaneously, the DOX and olaparib released synergistically induce DNA damage and cascade-activate the STING pathway. Chitosan itself also enhances STING signaling, thereby synergizing with the metabolic modulation by the engineered bacteria to further stimulate a potent antitumor immune response. Experimental results demonstrate that this hybrid robot can remodel the tumor immune microenvironment through multiple pathways and significantly enhance the therapeutic efficacy of anti-PD-L1 antibody therapy. This study provides a novel delivery strategy of EcLOX-CS@DOX-OLA with active targeting, metabolic modulation, and immune-activating functions for the combined treatment of bladder cancer.