H2O2-Responsive Gold Nanoclusters @ Mesoporous Silica @ Manganese Dioxide Nanozyme for “Off/On” Modulation and Enhancement of Magnetic Resonance Imaging and Photodynamic Therapy

In order to achieve safe and high-efficient photodynamic therapy (PDT), it was a powerful strategy of constructing O 2 -generated nanozyme with intelligent “off/on” modulation and enhancement. Herein, a kind of H 2 O 2 -responsive nanozyme was developed for off/on modulation and enhancement of magnetic resonance (MR) imaging and PDT, in which great amounts of gold nanoclusters (AuNCs) were loaded into mesoporous silica to form nanoassembly, and manganese dioxide (MnO 2 ) nanosheets were wrapped as switching shield shell ( [email protected] 2 @MnO 2 ). In a neutral physiological environment, stable MnO 2 shells eliminated singlet oxygen ( 1 O 2 ) generation to switch off PDT and MR imaging. However, in an acidic tumor microenvironment, the MnO 2 shell reacted with H 2 O 2, in which MnO 2 degradation switched on MR imaging and PDT, and the generated O 2 further enhanced PDT. H 2 O 2 -responsive MnO 2 degradation brought about excellent MR imaging with a longitudinal relaxation rate of 25.31 mM –1 s –1, and simultaneously sufficient O 2 generation guaranteed a 74% high 1 O 2 yield. Under the irradiation of a 635 nm laser, the viability of MDA-MB-435 cells was reduced to 4%, and the tumors completely disappeared, demonstrating strong PDT performance. Therefore, H 2 O 2 -responsive [email protected] 2 @MnO 2 nanozyme showed excellent off/on modulation and enhancement of MR imaging and PDT and was a promising intelligent nanoprobe for safe and high-efficiency theranostics.