Multifunctional Mesoporous Silica-Coated Hollow Manganese Oxide Nanoparticles for Targeted Optical Imaging, T₁ Magnetic Resonance Imaging and Photodynamic Therapy

We report the development of multi-functional uniform nanoparticles comprising a hollow manganese oxide core and a functionalized mesoporous silica shell (H–MnO@mSiO₂ (Ir)@–FA, Ir: an emissive iridium complex, FA: folic acid) for use as theranostic nanocomposites that combine four-in-one functionality, i.e., dual imaging (both magnetic resonance and optical), specific targeting and therapy in a single unit. The H–MnO@mSiO₂ (Ir)–FA nanoparticles (NPs) demonstrate its versatility in various applications. (1) The magnetic core provides the capability for T₁ magnetic resonance imaging. (2) Phosphorescent iridium complex serves as both photosensitizer and the luminescent chromophore. (3) The nano-channels in the mesoporous silica shell increase the free diffusion of oxygen and water permeability, enhancing photodynamic therapy (PDT) and T₁ signal, respectively. (4) Folic acid anchored on the outermost surface is able to target at specific cells for bimodal imaging and PDT. Proof of concept is provided in the in-vitro cell testing of H–MnO@mSiO₂ (Ir)–FA NPs, which demonstrates excellent targeting specificity, minimal collateral damage and highly potent therapeutic effect.