Surface d-Band Modulation via Biodirected Mineralization Enables Nanoenzymes to Inhibit Radiation-Induced T-Cell Exhaustion and Potentiate Immunoradiotherapy

Immunoradiotherapy (iRT) has emerged as a promising strategy for liver hepatocellular carcinoma (LIHC) treatment to synergistically activate both localized antitumor immunity and systemic immune responses. However, radiation will aggravate LIHC hypoxia, resulting in an adenosine metabolism level elevation, which promotes the differentiation of T cells into terminally exhausted phenotypes and weakens the efficacy of immunotherapy. To overcome this challenge, we engineered a nanocatalytic probiotic-based radiation-metabolic modulator, in which Escherichia coli Nissle 1917 (EcN) was programmed to in situ synthesize gold–palladium bimetallic nanocatalysts (EcNcGP) via biodirected mineralization. Guided by lattice mismatch and interfacial strain engineering, engineered EcN orchestrates the epitaxial assembly of Au atoms on Pd nanoclusters, yielding a precisely strain-tuned heterostructure with a modulated d-band electronic structure. This architectural design optimizes oxygen intermediate adsorption–desorption kinetics and significantly enhances the catalytic efficiency. This design enables EcNcGP to exhibit robust catalase- and peroxidase-like activities, which effectively catalyze intratumoral H₂O₂ into O₂ and hydroxyl radicals, intensifying radiation damage and alleviating tumor hypoxia to inhibit adenosine metabolism by downregulating the expression of ectonucleoside triphosphate diphosphate hydrolase 1 (CD39) and ecto-5′-nucleotidase (CD73). By blocking the binding of adenosine (ADO)–adenosine receptor A2A (ADORA2A) to inhibit the following cyclic adenosine monophosphate (cAMP)–protein kinase A (PKA)–phosphorylation of cAMP response element binding (pCREB) signaling transduction, radiation-induced T-cell exhaustion could be inhibited. Compared to stereotactic body radiotherapy (SBRT), the combination of EcNcGP with SBRT increased CD8⁺ T-cell infiltration by 99.8% and reduced PD-1^hi-exhausted T cells by 63.9%. Integration with anti-PD-L1 therapy (αPD-L1) achieved complete tumor regression in 60% of the treated mice-bearing orthotopic hepatocellular carcinoma. These findings establish a paradigm-shifting strategy for reprogramming tumor-immune metabolic checkpoints using strain-engineered nanocatalytic probiotics, thereby enhancing iRT and overcoming radioresistance.