Cytocompatibility Evaluation And Application Of Green Fluorescence Graphene Quantum Dots

Objective:To evaluate the cell compatibility of green fluorescent graphene quantum dots (GQDs) through improved photo-Fenton hydrothermal method, and investigate its application in biological imaging and physical therapy on tumor.Materials and Methods:The cytocompatibility of GQDs was estimated by examining the proliferation, membrane integrity, oxidative stress level and cell apoptosis of HeLa cells which was co-cultured 24 hours with different concentrations of GQDs. Cell morphology was observed by optical microscope. Cell uptake and the subcellular distribution of GQDs were further confirmed using transmission electron microscope. Fluorescent microscope and laser confocal microscopy were used to observe intracellular imaging and fluorescence of GQDs. FX-in vivo imaging system was used for imaging of nude mouse. Cell proliferation was tested after irradiation with NIR light. Cell proliferation, apoptosis and cell clone were observed after irradiation with heavy ion beam at different doses.Results:1. The cytotoxicity of GQDs showed dose-dependent. The cell viability was still higher than 80%. The intracllular total LDH content was nearly 80%. The ROS levels was 2.2 times to the control group,the necrosis and apoptosis cells was 15% when GQDs concentration at 200μg/mLThe cell morphology and amount did not significantly change.Transmission electron microscopy showed that GQDs entered into the cells via the endocytosis pathway and mainly located in the mitochondria and lysosome without destroying the integrity of the cell membrane.2.Cellular imaging results showed GQDs emit bright green fluorescence, and the fluorescence color shifted to middle pale yellow and grass green as time goes on, The fluorescence still emitted after six months later. GQDs presented bright green fluorescence in mice.3.The cell survival rate was significantly decreased after irradiation with NIR light. The IC50 was 27.791μg/mL. There were no significantly difference in the cell proliferation, apoptosis and cell clone after irradiation with heavy ion beam compared with the single cell group.Conclusions:The prepared graphene quantum dots has no obvious cytotoxicity and good biocompatibility. The GQDs entered into the cells via the endocytosis and mainly located in cytoplasm. It presented bright green fluorescence in the cells and mice with long-lasting fluorescence. Thus, these data offer a potential opportunity to develop GQDs for tracer imaging in biological and physical treatment.