Self-amplifying ROS nanorobot with orthogonal NIR activation for enhanced photodynamic–chemodynamic combination therapy

Abstract

While combination therapies generally exhibit superior therapeutic outcomes compared to single-modality treatments, current photodynamic–chemodynamic (PDT/CDT) combination strategies remain limited by two major factors: (i) the restricted tissue penetration depth of light and (ii) the insufficient endogenous hydrogen peroxide (H₂O₂) concentration within the tumor microenvironment (TME), both of which compromise therapeutic efficacy. To overcome these obstacles, we developed an innovative hybrid nanorobot (EcN + UCNPs@mSiO₂–MnO₂–ZnPc) that integrates engineered Escherichia coli Nissle 1917 (EcN) with orthogonally emissive upconversion nanoparticles (C@3S). Specifically, MnO₂ decomposes into Mn²⁺ under acidic TME conditions, subsequently catalyzing the conversion of H₂O₂ into cytotoxic hydroxyl radicals (˙OH) and oxygen, which exhibits dual effects of tumor cell eradication and hypoxia alleviation. Meanwhile, C@3S transforms 980 nm laser radiation into blue-violet emission, activating the EcN that preferentially colonizes tumor regions and overexpresses respiratory chain enzyme II (NDH-II), thereby replenishing H₂O₂ in situ and sustaining chemodynamic therapy (CDT). Additionally, zinc phthalocyanine (ZnPc) is excited by the 808 nm-converted red emission to generate singlet oxygen (¹O₂), further enhancing reactive oxygen species (ROS) accumulation and amplifying oxidative stress in tumor cells. Collectively, our findings demonstrate significant tumor growth inhibition through this self-amplifying ROS-generation mechanism. This multifunctional hybrid nanorobot offers a promising platform for precision cancer therapy with spatiotemporal controllability.