Enzyme-like copper-encapsulating magnetic nanoassemblies for switchable T1-weighted MRI and potentiating chemo-/photo-dynamic therapy

Abstract

Photodynamic therapy (PDT) has become a promising cancer treatment due to in situ generation of cytotoxic reactive oxygen (ROS); however, it remains limited by the hypoxia of tumor microenvironment (TME) and penetration depth of laser. Herein, we developed a kind of GSH-/H2O2-responsive copper-encapsulating magnetic nanoassemblies (MNSs) for switchable T1-weighted magnetic resonance imaging (MRI) and enzyme-like activity potentiating PDT of cancer. MNSs were rationally constructed using the chelation effect of copper ions (Cu2+) with polyacrylic acid-coated ultrasmall iron oxide nanoparticles (UIONPs). After uptake by tumor cells, the incorporated Cu2+ of MNSs was reduced to Cu+ through the intracellular GSH, which resulted in the disassembly of MNSs accompanied by the “silenced” MR signal shifting to a positive state. Sequentially, the generated Cu+ manifested peroxidase-like activity, catalyzing local H2O2 in TME to cytotoxic ·OH for chemodynamic therapy. Furthermore, Cu2+ and UIONPs could decompose H2O2 to O2, thus providing extra oxygen necessary for enhancing the PDT effect of photosensitizer IR-780. Finally, IR-780-loading MNSs (MNSs@IR-780) under laser irradiation significantly inhibited tumor growth and prolonged the survival of gastric MGC-803 tumor-bearing mice. Therefore, this study provides a versatile nanoplatform as a tumor-responsive theragnostic agent. Statement of significanceTumor hypoxia and penetration depth of laser severely hindered the PDT of cancer. Valence-convertible metal ions (VCMI, e.g., Cu2+/Cu+, Fe3+/Fe2+) have been reported as Fenton-like agents disintegrating H2O2 to O2 to enhance PDT. Tumor-delivery of VCMI is of essential importance for in situ triggering of a Fenton-like reaction. We thereby developed magnetic nanoassemblies (MNSs) to encapsulate Cu2+ and load photosensitizer (IR-780). Stimulated by GSH and H2O2, MNSs performed catalase/peroxidase-like activity that provided extra O2 for PDT and catalyzed H2O2 to ·OH for CDT. Consequently, IR-780-loading MNSs under laser irradiation significantly inhibit the tumor growth due to effective tumor delivery of Cu2+ and IR-780. This study might offer a feasible nanoplatform for tumor-delivery of metal ions and drugs.