Tannic acid-mediated synthesis of flower-like mesoporous MnO(2) nanostructures as T(1)–T(2) dual-modal MRI contrast agents and dual-enzyme mimetic agents

This study introduces a simple method for preparing a new generation of MnO(2) nanomaterials (MNMs) using tannic acid as a template. Two shapes of MnO(2) NMs, flower-like M1-MnO(2) and near-spherical M2-MnO(2), were prepared and compared as dual-active nanozymes and contrast agents in magnetic resonance imaging (MRI). Various parameters, including the crystallinity, morphology, magnetic saturation (M(s)), surface functionality, surface area, and porosity of the MNMs were investigated. Flower-like M1-MnO(2) NMs were biocompatible and exhibited pH-sensitive oxidase and peroxidase mimetic activity, more potent than near-spherical M2-MnO(2). Furthermore, the signal intensity and r(1) relaxivity strongly depended on the crystallinity, morphology, pore size, and specific surface area of the synthesized MNMs. Our findings suggest that flower-like M1-MnO(2) NM with acceptable dual-enzyme mimetic (oxidase-like and peroxidase-like) and T(1) MRI contrast activities could be employed as a promising theranostic system for future purposes.