Preparation And Application Of Fluorescent Bio-quantum Dots

Biological quantum dots(bio-dots) and carbon quantum dots(CQDs) are the novel fluorescent nanomaterials, which have very obvious advantages compared with traditional semiconductor quantum dots. In addition to the excellent optical performance, bio-dots and CQDs also has low toxicity, environmentally friendly, simple preparation method and low cost advantages, make them highly promising nanomaterials for chemical sensing and biosensing. In this paper, we have successfully prepared fluorescent bio-dots and CQDs, and revealed the basic characteristics by a series of characterizations, and deeply explored their applications in analytical chemistry.The main research content is as follows:(1) Hydrothermal preparation of novel fluorescent bio-dots from poly-cytosine DNA. The obtained bio-dots were characterized by transmission electron microscope(TEM), atomic force microscopy(AFM), indicating that bio-dots are rather uniform with an averaging diameter about 16 nm, the topographic height is about 0.8 nm. Composition and element analysis of the bio-dots were conducted by X-ray photoelectron spectroscopy(XPS), bio-dots well retain the heterocyclic rings of DNA and probably maintains certain important characteristics of DNA such as the formation of metal ion- mediated base pairs(C-Ag+-C). Through the fluorescence spectrum(FL) characterization, the bio-dots shows an excitation-independent emission behavior with a maximum emission at 420 nm. The ambient light had little influence on the FL of bio-dots, however, the FL is p H-dependent.(2) Bio-dots combined with Ag+ as FL sensing platform for the detction of glutathione(GSH), glutathione reductase(GR). By investigating on the relationship between the optical properties of bio-dots and the base number/base arrangement of DNA, we select an appropriate DN A sequence for the preparation of bio-dots. Taking advantage of biological activity of bio-dots, Ag+ can bind with the cytosine of bio-dots to form C-Ag+-C complex, resulting in the destroying of the luminescence centers of fluorescent bio-dots and thus the FL quenching. With the additon of biothiols, Ag+ prefers to react with biothiols to form the Ag+-S bond because of the strong affinity of Ag+ with thiols rather than bio-dots, and hence a restoration of FL emission can be observed. Moreover, based on the classic GR-catalyzed enzymatic reaction, GR, oxidized glutathione(GSSG) detection and inhibitor screening can be also facilely realized.(3) By employing uric acid as carbon source materials, we have proposed a method for the hydrothermal preparation of fluorescent CQDs for detecting copper ion, which is the important trace eleme nts in many biological processes. Copper is considered to be one of the important trace elements in many biological processes, participation in the process of life. Excessive copper ions will destroy the metabolic balance in the body result in a series of diseases such as Menkes’ disease, Wilson disease and Alzheimer disease. It is speculated that the nitrogen and oxygen of CQDs can bind with Cu2+ to result in the FL quenching which could be applied to Cu2+ sensing with the linear range of 1-15 μM.