Double-Sensitive Drug Release System Based on MnO₂ Assembled Upconversion Nanoconstruct for Double-Model Guided Chemotherapy

A double-sensitive drug release system based on MnO2 nanosheets was synthesized using a facile method for imaging guided chemotherapy in cancer cells. The upconversion nanoparticles (UCNPs) as core are used for upconversion luminescence (UCL) imaging, and the coating of mesoporous silica shows excellent ability for loading drug. The assembly with MnO2 nanosheets can respond to low intracellular pH and GSH in cancer cells. The obtained UCNPs@mSiO2–MnO2 nanoparticles with excellent biocompatibility can be applied as drug carriers. As expected, the UCNPs@mSiO2(DOX)–MnO2 (UCDMs) nanoconstruct loading with DOX offer practical chemotherapeutic effects in vitro, suggesting the active drug release in cancer cells. The luminescence intensity and magnetic resonance signals increased with the decomposition of the MnO2 nanosheets and the release of DOX under low pH and high levels of GSH. In addition, the UCDMs exhibit excellent intracellular UCL imaging, indicating that they can be used as a selective imaging agent in a cancerous environment. Thus, the UCDMs present potential application for use as theranostic agents in imaging guided therapy.