Zwitterionic Polydopamine-Coated Manganese Oxide Nanoparticles with Ultrahigh Longitudinal Relaxivity for Tumor-Targeted MR Imaging

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We present the design of antifouling zwitterion-functionalized manganese oxide (Mn 3 O 4 ) nanoparticles (NPs) modified with folic acid (FA) for targeted tumor magnetic resonance (MR) imaging. In the current work, diethylene glycol-stabilized Mn 3 O 4 NPs were initially prepared via a solvothermal approach, coated with polydopamine (PDA), fluorescently labeled with rhodamine B, conjugated with FA via amide bond formation, and finally covered with zwitterions of l -lysine (Lys). The thus-generated multifunctional Mn 3 O 4 NPs display excellent water dispersibility and colloidal stability, good protein resistance ability, and desirable cytocompatibility. With the PDA and Lys modifications, the multifunctional Mn 3 O 4 NPs own an ultrahigh r 1 relaxivity (89.30 mM –1 s –1 ) and enable targeted tumor MR imaging, owing to the linked FA ligands. The designed antifouling zwitterion-functionalized Mn 3 O 4 NPs may be employed as an excellent MR contrast agent for targeted MR imaging of other biological systems.