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

Abstract

The recent development of nanoprobes with multiple functionalities has attracted considerable interests for various biomedical applications. [1] The Fe 3 O 4 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 Fe 3 O 4 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 Fe 3 O 4 @chitosan-graphene quantum dots (Fe 3 O 4 @CS-GQDs) NPs which are demonstrated to be a fluorescence and MRI contrast agent. The Fe 3 O 4 NPs were fabricated by hydrothermal synthesis and had an average diameter of 9 nm. Next, the Fe 3 O 4 NPs were dispersed in chitosan solution to obtain the Fe 3 O 4 @CS NPs. Then, the Fe 3 O 4 @CS-GQDs NPs were synthesized by crosslinking between carboxyl groups of GQDs and amine groups of Fe 3 O 4 @CS. [2] The magnetic property and fluorescence of Fe 3 O 4 @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 Fe 3 O 4 @CS-GQDs NPs. The PL spectrum of Fe 3 O 4 @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 Fe 3 O 4 @CS-GQDs NPs have both fluorescent emission and superparamagnetic properties. The $\mathrm {T}_{2} -$weighted MRI of Fe 3 O 4 @CS-GQDs NPs were taken on a 3 T clinic MRI scanner. As shown in Figure 2a, the T 2 signal intensity decreased significantly with increasing Fe concentration, which indicates the Fe 3 O 4 @CS-GQDs NPs to be a promising contrast agents for MRI applications. To investigate the biocompatibility of the nanoprobes, the cytotoxicity of Fe 3 O 4 @CS NPs and Fe 3 O 4 @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 $50\mu \mathrm {g}/$mL Fe 3 O 4 @CS NPs and Fe 3 O 4 @CS-GQDs NPs. Therefore, the Fe 3 O 4 @ CS-GQDs NPs were demonstrated to be a potential dual-modal MRI contrast agent and fluorescence probes with high biocompatibility.