Design and Synthesis of "All-in-One" Multifunctional FeS2 Nanoparticles for Magnetic Resonance and Near-Infrared Imaging Guided Photothermal Therapy of Tumors

The ideal theranostic nanoplatform for tumors is a single nanoparticle that has a single semiconductor or metal component and contains all multimodel imaging and therapy abilities. The design and preparation of such a nanoparticle remains a serious challenge. Here, with FeS2 as a model of a semiconductor, the tuning of vacancy concentrations for obtaining "all-in-one" type FeS2 nanoparticles is reported. FeS2 nanoparticles with size of approximate to 30 nm have decreased photoabsorption intensity from the visible to near-infrared (NIR) region, due to a low S vacancy concentration. By tuning their shape/size and then enhancing the S vacancy concentration, the photoabsorption intensity of FeS2 nanoparticles with size of approximate to 350 nm (FeS2-350) goes up with the increase of the wavelength from 550 to 950 nm, conferring the high NIR photothermal effect for thermal imaging. Furthermore, this nanoparticle has excellent magnetic properties for T-2-weighted magnetic resonance imaging (MRI). Subsequently, FeS2-350 phosphate buffer saline (PBS) dispersion is injected into the tumor-bearing mice. Under the irradiation of 915-nm laser, the tumor can be ablated and the metastasis lesions in liver suffer significant inhibition. Therefore, FeS2-350 has great potential to be used as novel "all-in-one" multifunctional theranostic nanoagents for MRI and NIR dual-modal imaging guided NIR-photothermal ablation therapy (PAT) of tumors.