Engineered Bacteria-Driven Biohybrid Microrobots Potentiate IL-2 Immunotherapy by Evoking Pyroptosis

Interleukin-2 (IL-2) immunotherapy offers considerable potential for metastatic cancers; however, its efficacy is limited by low response rates, dose-dependent toxicity, short half-life, poor tumor accumulation, and off-target immune activation. In this work, we present a biohybrid microrobot (IL-2@Z/C/A) engineered through biomimetic mineralization of IL-2 variant-secreting Escherichia coli Nissle 1917 (EcN) with a zeolitic imidazolate framework-8 (ZIF-8) shell coloaded with an aggregation-induced emission photosensitizer and catalase. The ZIF-8 coating preserves bacterial viability tumor-homing capability while preventing premature drug leakage and systemic exposure, thus minimizing off-target effects. Upon accumulation in the acidic tumor microenvironment (TME), the framework degrades to release engineered bacteria and therapeutic cargo. Locally delivered zinc ion release, light-triggered reactive oxygen species and EcN derived pathogen-associated molecular patterns act synergistically to induce Cle-caspase/GSDMD mediated pyroptosis, resulting in immunogenic cell death accompanied by damage-associated molecular pattern release and pro-inflammatory cytokine production. Simultaneously, catalase-driven oxygen generation alleviates hypoxia and suppresses HIF-1α-induced immunosuppression. In combination with PD-L1 blockade, IL-2@Z/C/A achieves near-complete tumor regression in a B16F10 melanoma model via a coordinated immune cascade: pyroptosis-mediated antigen exposure primes adaptive immunity, hypoxia reversal counteracts immunosuppression, and sustained local IL-2 release reverses T cell exhaustion, collectively reprogramming the immunosuppressive TME and eliciting strong antitumor immunity. This work establishes a distinct paradigm for spatially controlled immunotherapy and highlights the potential of this biohybrid microrobot in converting immunologically "cold" tumors into responsive niches.