荧光石墨烯量子点制备及其在细胞成像中的应用

Preparation of Fluorescent Graphene Quantum Dots as Biological Imaging Marker for Cells

利用电化学方法在碱性条件下电解石墨棒,通过常温下水合肼还原,得到5～10 nm的荧光石墨烯量子点(Graphene Quantum Dots,GQDs).通过透射电子显微镜(TEM)、原子力显微镜(AFM)对所制备的GQDs进行形貌表征,GQDs的粒子大小均一,为单层石墨烯.通过傅里叶变换红外光谱(FTIR)、荧光光谱(PL)、紫外可见吸收光谱(UV-vis)、X射线衍射光谱(XRD)对所制备的GQDs进行性质测定,发现GQDs可以发出黄色荧光,量子产率为14%,毒性低、具有良好的水溶性、荧光稳定性和生物兼容性,可顺利进入细胞,在肿瘤细胞的成像研究方面具有广泛的应用前景.

Currently, graphene has attracted much attention in the fields of bioimaging, biolabeling and drug delivery. Theoretical and experimental studies have shown that the graphene quantum dots （GQDs） are expected to show good optical properties due to their quantum confinement and edge effect. In this report, using the electrochemical assay the fluorescent GQDs with a diameter between 5 and 10 nm could be obtained via electrolysing graphite in alkaline condition and with hydrazine hydrate as a reducing agent at room temperature. The structure of the GQDs was confimed by means of transmission electron microscope （TEM） and atomic force microscope （AFM）. The finding showed that the GQDs have an uniform size, and most of them are separate graphene. The GQDs mainly consist of single layer with less than 1 nm. Their features and properties were characterized by fourier transform infrared spectroscopy （FTIR）, photoluminescence spectra （PL）, UV-visible spectroscopy （UV-vis） and X-ray diffraction （XRD）. The results indicated that the GQDs have bright yellow luminescence with a 14 % quantum yield, which is higher than that of traditional carbon quantum dots reported previously. When they were excited by different excitation wavelengths, the intensity of photoluminescence increased to the maximum, and then decreased gradually. The fluorescent emission peak of the GQDs remained unshifted, suggesting a novel kind of quantum dots different from those of graphene oxide quantum dots depending excitation wavelengths. The luminescence of GQDs arises from the graphene modified with the phthalhydrazide-like groups and hydrazide groups at the edge. The highly fluorescent GQDs have high water solubility, good photostability and biocompatibility, indicating that the GQDs can easily enter the cells. By incorporating the GQDs with A549 （lung cancer） and MCF-7 （breast cancer） cells through MTT assay, the newly obtained GQDs exhibited low cytotoxicity with an advantage of strong photoluminescence in the cells, and thus the GQDs might be used as a bioimaging marker in tumor cell imaging.