Herein, multifunctional nanoparticles (MnIO-MCP) have been constructed for active-tumor-targeting T 1weighted and T 2 -weighted (T 1 −T 2 ) dual-modal magnetic resonance imaging (MRI)-guided bio-photothermal therapy (bio-PTT) through bioconjugation of the monocyclic peptides (MCP, the CXC chemokine receptor 4 (CXCR4) antagonist) with manganese-doped iron oxide nanoparticles (MnIO NPs). MnIO-MCP displays both T 1 -weighted and T 2 -weighted MR contrast abilities (r 1 = 13.1 mM −1 S −1 ; r 2 = 46.6 mM −1 S −1 , and r 2 /r 1 = 3.56), allowing generation of enhanced T 1 −T 2 dual-modal MRI. The MnIO-MCP exhibits reasonable photothermal conversion efficiency (28.8% with 200 μg mL −1 MnIO-MCP in H 2 O) under 808 nm NIR laser irradiation, endowing them with the capacity for PTT of a tumor. Moreover, MnIO-MCP affords the strong tumor-targeting and inhibition of cancer cell growth by the interactions of MCP with overexpressed CXCR4 in the tumor. We demonstrate that MnIO-MCP can accumulate in MCF-7 tumors as high as ∼15.9% ID g −1 at 1 h after intravenous injection into mice with the aid of an external magnetic field (MF), creating the opportunity for complete eradication of the tumor by T 1 −T 2 dual-modal MRI-guided bio-PTT.

The integration of two-dimensional (2D) nanosheets with biocompatible photothermal nanoparticles may produce effective multifunctional nanotheranostic agents.