A Sequentially Activated Nanoreactor With DNAzyme Cascade for Precise Breast Cancer Theranostics

Current oncological interventions are often limited by insufficient tumor selectivity and off-target toxicities, necessitating intelligent therapeutic platforms with precision-gated activation. In this study, a sequentially activated nanoreactor (GOx-MnCaP-DD) is designed for integrated breast cancer theranostics, combining precision chemotherapy with starvation-enhanced chemodynamic therapy (CDT). The platform is constructed by biomineralizing glucose oxidase (GOx)-templated manganese-doped calcium phosphate (MnCaP), followed by surface functionalization with DOX-encapsulated DNA hairpins (H1 and H2). In the acidic tumor microenvironment, the MnCaP scaffold first degrades, releasing the payloads and exposing the DNA hairpins. Subsequently, overexpressed miRNA-21 triggers H1 hybridization, initiating DOX release and exposing a functional DNAzyme sequence. With Mn²⁺ as a cofactor, the DNAzyme continuously cleaves H2, enabling cascade-amplified DOX release for sensitive miRNA detection (limit of detection: 210 fM) and enhanced chemotherapy. Simultaneously, GOx-mediated glucose depletion induces starvation while generating gluconic acid and H₂O₂, which accelerates nanoreactor disintegration and fuels Mn²⁺-mediated CDT through a self-reinforcing loop. Both in vitro and in vivo studies demonstrate improved therapeutic specificity and antitumor efficacy, providing a sophisticated strategy for "smart" nanomedicines capable of autonomous signal amplification and synergistic treatment.