Methotrexate-Mn²⁺ based nanoscale coordination polymers as a theranostic nanoplatform for MRI guided chemotherapy

Theranostic nanoplatforms based on magnetic resonance imaging (MRI) technology have drawn much attention due to their inherent advantages such as non-invasiveness and high spatial resolution, but their construction is usually complicated and the compositions are uncontrollable. Herein, a simple and controllable theranostic nanoplatform by replacing a chelating agent with a chemotherapeutic drug directly was proposed. In detail, we elaborately synthesized Mn2+ and methotrexate (MTX) based nanoscale coordination polymers (NCPs) coated with poly(ethylene glycol) (PEG), MTX-Mn@PEG, in which Mn2+ ions served as MRI contrast agents (CAs), MTX was used as a chemotherapy drug and PEG provided a stable environment for nanoparticles, respectively. The obtained MTX-Mn@PEG NCPs showed a relatively uniform size, a pH-responsive feature and long blood circulation to enrich in the tumor location through the enhanced permeability and retention (EPR) effect. We determined the composition and coordination mechanism of MTX-Mn@PEG through thermogravimetric analysis (TGA), Fourier transform infrared (FI-TR) spectroscopy, powder X-ray diffraction (XRD) and so on. We determined the composition and coordination mechanism of MTX-Mn@PEG with the molar ratio of MTX to Mn2+ as 1 : 1. Then we confirmed that the antitumor ability was mediated by MTX through MTT and cell apoptosis assay in vitro. In vivo MR imaging and antitumor assays demonstrated the excellent effect of the NCPs in diagnosis and therapy of tumors. Overall, these novel MTX-Mn@PEG NCPs provide a theranostic nanoplatform for cancer treatment.