MnO2-Functionalized Co–P Nanocomposite: A New Theranostic Agent for pH-Triggered T1/T2 Dual-Modality Magnetic Resonance Imaging-Guided Chemo-photothermal Synergistic Therapy

Construction of stimuli-responsive theranostic nanoagents that can increase the accuracy of imaging diagnosis and boost the therapeutic efficacy has been demonstrated for a promising approach for diagnosis and treatment of cancer. Herein, we constructed a novel theranostic agent with Co–P nanocomposites as core, mesoporous silica as shell, and manganese dioxide (MnO2) nanosheets as gatekeeper, which have been employed for pH-activatable T1/T2 dual-modality magnetic resonance imaging (MRI)-guided chemotherapeutical and photothermal combination anticancer therapy in vitro and in vivo. Co–P core-enabled theranostic platform could be applied for both photothermal therapy and T2-weighted MRI in the normal circulation owing to its strong  near-infrared absorbance and intrinsic magnetic properties. In the acidic environment of tumors, MnO2 cap could be dissolved into Mn2+ ions to not only realize pH-responsive on-demand drug release but also activate T1-weighted MRI contrast enhancement. Such T1/T2 dual-mode MR imaging provides further comprehensive details and accurate information for tumor diagnosis, and the on-demand chemo-photothermal synergetic therapy greatly improved the therapeutic effectiveness and effectively mitigated side effects. These findings demonstrate that Co–P@mSiO2@DOX–MnO2 are promising as pH-responsive theranostic agents for tumor diagnosis and treatment, and stimulate interest in exploration of novel stimuli-responsive theranostic nanoagents which posssess good potential for clinical application in the future.