Facile Synthesis of Biocompatible Fe3O4-Based Nanoparticles for pH-Responsive Dual-Model Magnetic Resonance Imaging-Guided Tumour Eradication by Photothermal Therapy

The accurate and early diagnosis is very important for the successful treatment of tumours. However, a single mode of magnetic resonance imaging (MRI) is difficult to satisfy the high requirements of accurate diagnosis owing to the inherent defects. Herein, we constructed a kind of poly(acrylic) acid (PAA) modified Fe3O4@MnO2 nanoparticles (Fe3O4@MnO2@PAA NPs) for the pH-responsive T1/T2 dual-model MRI guiding photothermal therapy (PTT). The Fe3O4 core enabled Fe3O4@MnO2@PAA NPs to weaken T2 signal in clinical MRI examination, and MnO2 nanoshells were able to decompose into the paramagnetic manganous ions under the weakly acidic environment of tumours, achieving pH-responsive T1-weighted MRI. Such pH-responsive T1/T2 dual-model contrast agents (CAs) with high sensitivity and specificity provided more comprehensive information for diagnosis of tumours. Moreover, Fe3O4@MnO2@PAA NPs exhibited excellent absorption performance in near-infrared region (NIR), making them as a potential NIR photothermal agents for PTT. This work presented novel pH-responsive theranostic agents integrated dual-model imaging and PTT functionalities, and demonstrated their potential for stimuli-responsive MRI-guided PTT of cancer.