A bladder microenvironment-adaptive ceria nanozyme hydrogel enables urea-responsive intravesical chemo-immunotherapy

Bladder cancer intravesical therapy remains limited by rapid urinary washout, insufficient penetration across the bladder mucosal barrier, and an immunosuppressive tumor microenvironment. Here, we developed a bladder microenvironment-adaptive chemo-immunotherapy system, Gel/UCeNZ/Gem/CpG, to improve local bladder cancer treatment. In this system, urease-modified CeO₂ nanozymes (UCeNZ), gemcitabine (Gem), and CpG oligodeoxynucleotide (CpG ODN) were incorporated into an injectable thermosensitive adhesive hydrogel. After intravesical administration, the hydrogel rapidly formed a mucosa-adherent depot, thereby prolonging bladder residence and enabling sustained therapeutic release. Meanwhile, UCeNZ responded to endogenous urinary urea to enhance particle transport and mucosal penetration, improving local drug exposure beyond passive instillation. Functionally, CeO₂-mediated redox regulation amplified Gem-induced oxidative stress, mitochondrial dysfunction, apoptosis, and immunogenic cell death-associated signaling, as evidenced by HMGB1 translocation/release, calreticulin exposure, and intracellular ATP dysregulation. CpG ODN further promoted dendritic cell maturation and strengthened T cell-mediated antitumor immunity. In an orthotopic bladder cancer model, Gel/UCeNZ/Gem/CpG significantly suppressed tumor progression, prolonged survival, increased CD8⁺ T cell infiltration, reduced regulatory T cells and M2-like macrophages, and enhanced memory/effector-like T cell activation without obvious systemic toxicity. Transcriptomic analysis further revealed coordinated regulation of oxidative stress, apoptosis, antigen presentation, cytokine signaling, T cell activation, PD-1/PD-L1 checkpoint signaling, and p53-related tumor-suppressive pathways. Overall, this study presents a bladder-adaptive intravesical chemo-immunotherapy strategy that integrates mucosal retention, urea-responsive penetration, redox-amplified immunogenic chemotherapy, and immune microenvironment remodeling for bladder cancer treatment.