Porous MnFe2O4-decorated PB nanocomposites: a new theranostic agent for boosted T1/T2 MRI-guided synergistic photothermal/magnetic hyperthermia

Abstract

This study reports a multifunctional core/shell nanoparticle (NP) that can be used for amplified magnetic resonance image (MRI), enhanced photothermal therapy (PTT) and magnetic hyperthermia therapy (MHT) due to its surface coating with a porous shell. Importantly, by means of introducing the surface coating of a porous shell, it helps entrap large quantities of water around NPs and allow more efficient water exchange, leading to greatly improved MR contrast signals. Besides, the porous shell helps the near-infrared (NIR) absorbance of the core, and then the extremely enhanced thermal effect can be obtained under synergistic combination of PTT and MHT. By synthesizing multifunctional porous MnFe₂O₄/PB as an example, we found that the transversal relaxivity (r₂) of MnFe₂O₄ NPs might improve from 112.11 to 123.46 mM⁻¹ s⁻¹, and the specific absorption rate (SAR) of MnFe₂O₄/PB nanoparticles reached unprecedented levels of up to 4800 W g⁻¹ compared with the SAR 1182 W g⁻¹ of PTT under an 808 nm laser and 180 W g⁻¹ of MHT under an external AC magnetic field. Meanwhile, when MnFe₂O₄ was decorated on PB nanoparticles, the magnetic properties became lower slightly, but the synergistic photothermal/magnetic hyperthermia conversion was enhanced greatly. Subsequently, in vitro T₁–T₂ dual-modal MRI, PTT and MHT results verified that MnFe₂O₄/PB could serve as an excellent MRI/PTT/MHT theranostic agent. Furthermore, the MnFe₂O₄/PB NPs were applied as a T₁–T₂ dual-modal MRI, PTT and MHT theranostic agent for in vivo MRI-guided photothermal and magnetic hyperthermia ablation of tumors by intratumoral injection in 4T1 tumor-bearing mice. The T₁–T₂ dual-modal MR imaging result shows a significantly contrast in the tumor site. The MPB-mediated PTT and MHT result shows high therapeutic efficiency as a result of high photothermal and magnetic hyperthermia conversion efficiency. The multifunctional NPs have a great potential application for future clinical tumorous diagnosis and treatment.