Magnetic-Fluorescent Fe3O4@Chitosan-Graphene Quantum Dots Nanocomposites for Dual-Modal nanoprobes of Fluorescence and Magnetic Resonance Imaging.

摘要

The recent development of nanoprobes with multiple functionalities has attracted considerable interests for various biomedical applications. [1] The Fe₃O₄ Nanoparticles (NPs) are superparamagnetic and usually used as magnetic resonance imaging (MRI) contrast agents. The graphene quantum dots (GQDs), a new zero dimensional graphene nanomaterial, exhibit tunable photoluminescence property, excellent stability and biocompatibility. If the Fe₃O₄ NPs and GQDs can combine together, the composites are expected to be dual-modal nanoprobes of fluorescence and MRI. In this work, we study on the Fe₃O₄@chitosan-graphene quantum dots (Fe₃O₄@CS-GQDs) NPs which are demonstrated to be a fluorescence and MRI contrast agent. The Fe₃O₄ NPs were fabricated by hydrothermal synthesis and had an average diameter of 9 nm. Next, the Fe₃O₄ NPs were dispersed in chitosan solution to obtain the Fe₃O₄@CS NPs. Then, the Fe₃O₄@CS-GQDs NPs were synthesized by crosslinking between carboxyl groups of GQDs and amine groups of Fe₃O₄@CS. [2] The magnetic property and fluorescence of Fe₃O₄@CS-GQDs NPs were characterized by vibrating sample magnetometer measurements and photoluminescence (PL) spectroscopy. As shown in Figure 1a, the magnetization hysteresis loop shows a near zero coercivity, indicating the superparamagnetic property of Fe₃O₄@CS-GQDs NPs. The PL spectrum of Fe₃O₄@CS-GQDs NPs shown in Figure 1b exhibits a emission peak at 434 nm, which is under the excitation of ultraviolet 350nm. These results show that the Fe₃O₄@CS-GQDs NPs have both fluorescent emission and superparamagnetic properties. The $mathrm {T}_{2} -$weighted MRI of Fe₃O₄@CS-GQDs NPs were taken on a 3 T clinic MRI scanner. As shown in Figure 2a, the T₂ signal intensity decreased significantly with increasing Fe concentration, which indicates the Fe₃O₄@CS-GQDs NPs to be a promising contrast agents for MRI applications. To investigate the biocompatibility of the nanoprobes, the cytotoxicity of Fe₃O₄@CS NPs and Fe₃O₄@CS-GQDs NPs on Hela cells were studied with an MTT assay. According to Figure 2b, the viability of Hela cells is higher than 80% after 48 h of incubation with $50mu mathrm {g}/$mL Fe₃O₄@CS NPs and Fe₃O₄@CS-GQDs NPs. Therefore, the Fe₃O₄@ CS-GQDs NPs were demonstrated to be a potential dual-modal MRI contrast agent and fluorescence probes with high biocompatibility.