A Research For Constructing New Kinds Of Fluorescent Sensors Based On GQDs And SGI

The modern detecting techniques are developing to be rapid, sensitive and high throughput ones. At the same time, fluorescent technique is proving itself as a more and more popular analytical technology by it's easily operating, time-saving, sensitive,highly specific merits. What is more, the new fluorescent technique could evenly be developed to be a high thoughput biologically analytical technique. Currently, there are mainly two technology roadmap: One is the fluorescent biosensor labeled by fluorescence dye, which could be used for imaging and detecting. The labeling dye are usually FITC and FAM. The other one is fluorescent strategy based on development of fluorescent nano materials including semiconductor quantum dots and metal cluster,which has been widely used for the detection of DNA, protein etc.The present fluorescent biosensors usually need labeling modifications, which may lead to some shortcoming including waste of time and energy, high cost etc. Therefore,developing some label-free fluorescence detecting methods owning high sensitivity,high specificity may have a wide application prospect in the detections of many target analytes. Considering all above, this research has designed three different label-free fluorescence detecting strategies for three target analytes, which are as following:Chapter 1 A label-free fluorescence sensor based on GQDs for dopamine detectionIn this part, a label-free fluorescence sensor based on GQDs was designed for detection of dopamine. GQDs were prepared by directly pyrolyzing citric acid under certain conditions and used as fluorescenct probe; in alkaline buffer solution, DA's automatically polymerize to be pDA and snap to the surface of GQDs resulting in fluorescence quench; the fluorescence-quenching degree could be measured for dopamine detection; UV-vis ?FTIR?AFM?TEM?zeta potential?XPS were applied to a series of characterizations including the morphology of GQDs and pDA?FRET quenching mechanism etc. Under the optimal conditions, the linearity range and LODwere given as 0.01-60.0?M, 0.008?M respectively. This method could realize the detection of DA injection and the standard addition test of DA in serum samples. The results turned out that this method own a good selectivity and can test DA concetration accurately in complex systems, which could evenly provided a new choice for convinient DA detection in clinical practice.Chapter 2 A label-free fluorescence sensor based on SGI and ATP aptamer for ATP detectionIn this part, a label-free fluorescence sensing strategy based on SGI and aptamer was designed for detection of ATP. DNA aptamer owning certain sequence was designed for forming long-chain ds-DNA; Then ATP was added; when meeting ATP,the aptamer may generate a stable framework composed of two stacked G-quartets leading to the collapse of long-chain ds-DNA and the release of binding SGI; there is a positive correlation between the decrease of fluorescence intensity and the concentration of ATP, which could help realize the detection of ATP. Electrophoresis and imaging techniques were applied to the characterization of the quenching mechanism. Under the optimal conditions, the linearity range and LOD were given as10.0-5000.0?M, 6.1?M respectively. At the same time, the relative error analysis of the detecing results of the ATP in cancer cells by this method and ATP kits was done to study the practicality for real samples detecting. All the results turned out that this method could satisfy the accurate detection of ATP in real samples and could evenly provided a new strategy for ATP detecting in cells of complex systems.Chapter 3 A label-free fluorescence sensor based on SGI and GO for mercury ion detectionIn this part, a label-free fluorescence strategy was designed for detection of mercury ion based on SGI and GO. DNA probe of T-base mismatch was designed for the T-Hg-T reaction of mercury ion; Then fluorescence intensity of SGI binding to hairpin structure produced by T-Hg-T reaction was measured as the signal for mercury ion detection; GO was introduced to the reacting system to enhance the signal to noise ratio by decrease the fluorescence intensity of free SGI. Under the optimal conditions,there was a linear relation at a range of 10.0-2000.0nM and LOD were given as 2.2?M.Also, this method can realize the quantitative detection of mercury ion in water samples and could evenly be applied to fields such as, enviromental monitoring, analysis of pesticide residues, food and drug industries etc.