Preparation Of Graphene Quantum Dots For Bioimaging Applications

This paper aims to increase the fluorescence quantum yield of the Graphene Quantum Dots (GQDs) by improving the preparation conditions in hydrothermal processes of GQDs, and study the cellular imaging and small intestine imaging of GQDs in mice.The main contents and results of the paper are as follows:1. Preparation and characterization of GQDs:GQDs were prepared by hydrothermal processes with different GO/DMF ratio, filling percentage and reaction time. Photoluminescence intensity and fluorescence quantum yield of GQDs were tested by fluorescence spectrophotometer. The morphology of GQDs was characterized by the transmission electron microscopy; the optical properties of GQDs were characterized by the ultraviolet-visible spectrophotometer and fluorescence spectrophotometer. The results showed that the GO/DMF ratio of10mg/ml, the filling percentage of80%and the reaction time of12h were the best conditions for preparing GQDs. The fluorescence quantum yield of as-prepared GQDs was17.4%and the average particle diameter was3.783±0.829nm. The intensity of GQDs’ photoluminescence (PL) depended upon excitation wavelength, pH and concentrations.2. Cytotoxicity test of GQDs:The cytotoxicity of GQDs was tested by MTT assay, compared with cadmium telluride quantum dots (CdTe QDs). The results showed that cellular survival rates of two groups declined with the increase of concentrations, but the rates of CdTe QDs group dropped faster than that of GQDs, which indicated that the cellular cytotoxicity of GQDs was less than that of CdTe QDs.3. Cell imaging experiment of GQDs:GQDs and Tca-8113cells were Co-cultured and the cellular imaging was observed by the confocal microscopy. The results showed that brightly green fluorescence located in cells, which meant GQDs entered cells and imaged. 4. Small intestine imaging experiment of GQDs in mice:2mg/ml suspension of GQDs was given into mice by gavage. The imaging of small intestine was observed by Fx-in vivo imaging system, contrasted with barium. At the same time, the changes of microcirculation blood flow were observed by the microcirculation microscope. The results showed that brightly green fluorescence images with clear edge of intestinal mucosal were revealed under Fx-in vivo imaging system after mice received GQDs. Meanwhile, clearly green fluorescence images of mesenteric vessels were observed in the mice. Image formation of GQDs is better than that of barium meal in the intestinal wall of mice, and GQDs has less influence than that of barium meal in mesenteric microcirculation of mice.