Investigation On The Absorption Of Water-soluble ZnO Quantum Dots By Nuclear Analysis Technology

The ZnO semiconductor quantum dots (QDs) are new kind of biological tags materials, due to their broad excitation spectrum, narrow emission spectrum, precise adjustable emission peak and negligible bleaching. They are potentially used in protein analysis, cell imagination, nucleic acid detection. The water-soluble ZnO QDs was synthesized by Poly Ethylene Glycol (PEG) monomer, such copolymer shell make the whole nanoparticle water-soluble in water. However, whether the ZnO QDs structure is stable in vivo has not yet to be described, but it is crucial to the use of the QDs. With regard to this issue, some works and innovative results have been done as follow.Oral epidermoid carcinoma (KB) cells treated by ZnO quantum dots were studied by the Micro-PIXE technique. It is proposed that ZnO QDs were absorbed into KB cells. The XAFS method was applied to obtain information about zinc (Zn) K-edge spectra. XANES spectra of Zn K-edge for ZnO QDs in KB cells was identical with ZnO QDs standard sample. The fits of the EXAFS data showed that the Zn-0bond and Zn-Zn bond structure of water-soluble ZnO QDs were stable after being absorbed by KB cells. Its local structural parameters were almost identical with those of the wurtzite structural data. Water-soluble ZnO QDs had good structural stability in KB cells. The EXAFS results indicated that the structural disorder(σ2) in ZnO QDs rised as the size decrease from4nm to3nm. There were some differences between XANES of the ZnO QDs and that of ZnO crystal.Secondly, Micro-PIXE and ICP-AES were applied in the hyperaccumulating plant (Sedum alfredii Hance) to investigate the characteristics of Zn distribution in the stems and leaves. The stem sections were investigated by Micro-PIXE, the results indicated that Zn was preferential accumulated in stem epidermis and vascular bundles. Stem distribution patterns of Ca、K in the Sedum alfredii Hance were very like that for Zn, but the P distribution pattern was little different with the Zn pattern. There is no change in Zn distribution of the Sedum alfredii Hance treated by ZnO QDs. The Zn enrichment in Sedum alfredii Hance stem treated by ZnO QDs is higher than that in the control group, however, we can’t find the ZnO QDs in the stem sections under ultraviolet light. Thus, there was no enough evidence to prove the ZnO QDs were stored in Sedum alfredii Hance. The growth of the plant suggests that the ZnO QDs have a good biocompatible property. In summery, Micro-PIXE combined with XAFS were proven to be a credible and precise tool for investigating the quantum dots’distribution in biological systems. In addition, our work is benefit to the future application of the ZnO QDs in biological and environmental area. These ZnO QDs, as a type of safe and cheap luminescent labels, have an inspiring prospect in biological applications.