Mn-Doped Calcium Phosphate Nanoclusters with Enhanced Ability of Valence Adjustment for MRI Guided Sequential Therapy of Tumors from PTT to CDT

Constructing tumor microenvironment (TME) responsive-nanoplatforms with controllable structure is a promising strategy for tumor treatment. Considering the magnetic, near-infrared absorption, Fenton-like catalytic property of Mn ions, and favorable biocompatibility of calcium phosphate (CaP), Mn-doped CaP nanoclusters (MnCaP NCs) were prepared with poly acrylic acid. MnCaP NCs showed enhanced magnetic resonance imaging (MRI) and chemodynamic therapy (CDT) with strong surface effects. Most intriguingly, partial Mn2+ in MnCaP NCs could be oxidized to Mn4+ during the preparation process, which endows MnCaP NCs with photothermal (PTT) properties. After photothermal therapy, Mn4+ can be reduced to Mn2+ again by glutathione (GSH) to further enhances CDT and MRI efficiency. In summary, MnCaP NCs represented complete tumor growth suppression in tumor-bearing mice after a 14-day therapy, demonstrating that biocompatible MnCaP NCs would be a competitive theranostic nanomaterial for MRI-guided PTT-CDT sequential therapy for tumors.