DNA-Templated Silver Nanocluster/Porphyrin/MnO2 Platform for Label-Free Intracellular Zn2+ Imaging and Fluorescence-/Magnetic Resonance Imaging-Guided Photodynamic Therapy

Developing a theranostic platform that integrates diagnosis and treatment in one single nanostructure is necessary for efficient tumor treatment. Here, we presented a novel theranostic nanoprobe for nonlabeled fluorescence imaging of Zn2+ and 635 nm red light-triggered photodynamic therapy (PDT) by a multifunctional DNA-templated silver nanocluster/porphyrin/MnO2 nanoplatform. MnO2 nanosheets adsorbed hairpin DNA-silver nanoclusters (AgNCs) and porphyrin (P) by facile physisorption, which accelerate the transfection of nanoprobes and P into tumor cells. After entering the cells, the biodegradation of MnO2 nanosheets by glutathione and acidic hydrogen peroxide released AgNCs for label-free Zn2+ fluorescence imaging by the hairpin DNA-fueled dynamic self-assembly of three-way DNA junction architectures, and the released Mn2+ could act as an effective magnetic resonance imaging (MRI) contrast agent. In addition, MnO2 was decomposed in the acidic H2O2-ample environment and produced O2 to overbear hypoxia-related PDT resistance, highly efficient PDT was obtained by excess singlet oxygen (1O2) release of P-AgNCs-MnO2 nanoprobes under light irradiation compared with free P. In vitro and in vivo studies confirmed that P-AgNCs-MnO2 exhibited high fluorescence specificity, excellent PDT effect, and good biocompatibility and could be used as a contrast agent for MRI. This theranostic platform provided a new avenue for the fluorescence and MRI diagnosis of tumors and efficient tumor treatment.