A Responsive Biomimetic Nanoagonist for Pyroptosis Induction and Controlled Resiquimod Release to Enhance Tumor Photoimmunotherapy.

Abstract

Immune suppression of tumor microenvironment (TME) limits the effectiveness of the immune therapy. Although inducing tumor cell pyroptosis and activating innate immunity are effective strategies to reverse this microenvironment, current methods are often hindered by non-targeted toxicity and the inability to precisely control drug release. To address these challenges, we synthesized an ROS-responsive R848 prodrug with a maleimide structure. Then, Hemin was coupled to bovine serum albumin (BSA) and the disulfide bonds within the BSA molecule were reduced, exposing free thiol groups. The R848 prodrug was then conjugated to the thiol groups, and the photosensitizer Ce6 was loaded, allowing self-assembly into the HBSA@CR nanoagonist. This strategy not only achieved a higher drug loading capacity than traditional albumin nanoparticles, but also retained the biocompatibility of natural albumin and the advantages of receptor-mediated cellular uptake. HBSA@CR can be activated by 660 nm laser irradiation to efficiently generate ROS through photodynamic and enzymatic catalysis. In vitro experiments show that this nanoparticle can efficiently kill tumor cells, induce pyroptosis through the Caspase-3/GSDME pathway and trigger the release of R848. In tumor-bearing mouse models, HBSA@CR effectively inhibited primary tumor growth and lung metastasis, and reprogrammed the immunosuppressive TME. In a tumor rechallenge model, this strategy prevented tumor recurrence and conferred long-lasting immunological memory. Moreover, when used in combination with the immune checkpoint inhibitor αPD-L1, this nanoparticle exhibits synergistic therapeutic effects. The designed nanoagonist offers a biomimetic platform for combined photo-immunotherapy, which achieves controlled R848 release while inducing tumor cell pyroptosis, reprogramming the immunosuppressive TME, and eliciting durable antitumor immunological memory. STATEMENT OF SIGNIFICANCE: The immunosuppressive tumor microenvironment is one of the main obstacles to effective immunotherapy, severely restricting the clinical efficacy. Inducing pyroptosis and stimulating innate immune activation are effective strategies for reprogramming the tumor microenvironment, but existing methods often face problems such as the lack of selectivity in inducing pyroptosis and the high toxicity of systemic administration of immune agonists. In this study, a nanoagonist HBSA@CR was constructed, which retains the biocompatibility and receptor-mediated tumor uptake of native albumin. This nanoplatform utilizes ROS to induce tumor cell pyroptosis and drive the controlled release of R848, achieving precise local pyroptosis induction and innate immune activation, effectively reprogramming the immunosuppressive microenvironment and stimulating persistent anti-tumor immune memory.