Multifunctional Core@Shell Magnetic Nanoprobes for Enhancing Targeted Magnetic Resonance Imaging and Fluorescent Labeling in Vitro and in Vivo.

Core@shell magnetic nanoparticles (core@shell MNPs) are attracting widespread attention due to their enhancement properties for potential applications in hyperthermia treatment, magnetic resonance imaging (MRI), diagnostics, and so forth. Herein, we developed a facile thermal decomposition method for controllable synthesis of a superparamagnetic, monodispersed core@shell structure (Co@Mn = CoFe2O4@MnFe2O4) with uniform size distribution (σ < 5%, dc ≈ 15 nm). The CoFe2O4 core could enhance magnetic anisotropy, and the MnFe2O4 shell could improve the magnetization value. The Co@Mn MNPs were transferred into aqueous solution with an amphiphilic polymer (labeled 2% TAMRA) and functionalized with PEG2k and target molecules (folic acid, FA) to fabricate multifunctional PMATAMRA-Co@Mn-PEG2k-FA nanoprobes. The obtained PMATAMRA-Co@Mn-PEG2k-FA nanoprobes exhibit good biocompatibility, high T2 relaxation values, and long-term fluorescence stability (at least 6 months). Our results demonstrate that the synthesized PMATAMRA-Co@Mn-PEG2k-FA nanoprobes can effectively enhance the targeted MRI and fluorescent labeling in vitro and in vivo. The research outcomes will contribute to the rational design of new nanoprobes and provide a promising pathway to promote core@shell nanoprobes for further clinical contrast MRI and photodynamic therapy in the near future.