Fe3O4-rhodamine 6G nanoparticles: An iron enhanced pH sensitive multimodal probe for fluorescence and magnetic resonance imaging of tumor cell

Abstract

The accurate diagnosis of tumor at the early stage depends on efficient medical imaging methods using probes with high sensitivity to the environment of tumor cells. For this purpose, we design the Fe3O4-rhodamine 6 G (Rh6G) nanoparticles (NPs) as a kind of dual-mode probe for fluorescence and magnetic resonance imaging (MRI). The Fe3O4-Rh6G NPs are demonstrated to be Fe3+ enhanced and pH-sensitive fluorescent agents, and the strongest fluorescence performance occurs under the pH value of 3. Cytotoxicity assessment in HeLa cells proves the good biocompatibility and low toxicity of the Fe3O4-Rh6G NPs. The consequent fluorescence experiments in tumor cells show good imaging contrast, which is contributed by both the Fe3+ released from Fe3O4 and the acid environment of tumor cells. Moreover, the Fe3O4-Rh6G NPs are superparamagnetic and have a strong MRI T2 contrast effect. According to the performance in fluorescence and MRI tests, the Fe3O4-Rh6G NPs are potential dual-mode probes for MRI contrast agents and fluorescence probes with high biocompatibility for early-stage tumor detection.