Engineered Self-Activatable Polymeric Nanozymes Precisely Eradicate Tumor-Associated Intramacrophage Bacteria to Potentiate Immunotherapy Based on Cluster of Differentiation 47 Blockade

Abstract

Immunotherapy for colorectal cancer (CRC) remains clinically limited by a profoundly immunosuppressive tumor microenvironment. Fusobacterium nucleatum (Fn), which selectively colonizes CRC tumors, drives this immunosuppression by persisting within macrophages and driving their M2 polarization. Here, we engineered a self-activatable polymeric nanozyme comprising ferrocene-bearing glycopolymers with artesunate (AS) payloads to eliminate intramacrophage Fn reservoirs and reprogram the macrophage immune ecosystem. These nanozymes were specifically engulfed by M2-like Fn-infected macrophages via mannose receptor-mediated endocytosis and then activated by overexpressed intracellular hydrogen peroxide to release ferrous ion and AS, which synergistically amplified cytotoxic reactive oxygen species (ROS) generation through Fenton chemistry. Concurrently, AS induced macrophage autophagy, promoting nanozyme-bacteria colocalization in autophagolysosomes to enhance ROS-mediated Fn killing. Remarkably, intracellular Fn eradication not only reversed the immunosuppressive phenotype of infected macrophages but also triggered paracrine signaling that drove M1 repolarization of neighboring uninfected macrophages. In both xenograft and orthotopic CRC models harboring intracellular Fn, the nanozymes can efficiently eliminate intracellular Fn and systemically remodel the macrophage immune landscape, significantly boosting the therapeutic efficacy of anti-CD47 immunotherapy. This work presents a strategy for improving CRC immunotherapy through precise targeting of tumor-associated intramacrophage bacteria.