Cellulose hydrogel is a novel carbon-source and doping-material-carrier to prepare fluorescent carbon dots for intracellular bioimaging

Abstract

Carbon dots (CDs) is considered as a potential candidate for biological labeling due to its excellent biocompatibility, and element-doping was usually used to improve its labeling brightness. Thus, the carbon source with material-carried function will be of importance to produce the element-doped CDs. In present work, cellulose hydrogel was used both as the carbon source and the doping-material-carrier to obtain the N-doped CDs. The groups in so-obtained CDs were measured by means of ultraviolent-visible spectrophotometer (UV–Vis), Fourier infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy. The microstructure of CDs was observed by means of high-resolution transmission electron microscope. The fluorescence quantum yield (QY) of the CDs was detected, and the labeling brightness on living cells was subsequently investigated. Finally, the influence of element-doping on the cytotoxicity was measured. The experimental results showed that Cellulose hydrogel is a nice carbon source and doping-material-carrier to produce fine N-doped CDs due to its distinct spatial network structure. The carried NaOH and urea in cellulose hydrogel significantly improved the QY of the CDs from 0.0542 ± 0.0030 to the maximum 0.1965 ± 0.0013. For the same kind of CDs, the smaller the particle size is, the higher the QY value is. The CDs immobilized in the cytoplasm of the living cells, and contributed to a non-specific fluorescent labeling. The labeling brightness is both the QY value of the CDs and the uptake rate of the living cells dependent. For the same cell line, the QY of CDs and the labeling brightness of living cells are significantly linear correlated. The cytotoxicity of CDs is low enough for a long-time observation on living cells.