| E. coli 0157:H7 is a strong virulence intestinal pathogens and spread mainly through water and food, which is one of the main causes of food poisoning. The infection usually have bloody diarrhea, hemolytic uremic syndrome. Rapid detection of Escherichia coli in food production and food circulation has became the focus of the study. Quantum dots are diameter in 1-10 nm semiconductor nanoparticles. QDs emission is size dependent. The unique optical properties of QDs, such as photostability for long periods, broad absorption, narrow, very specific, stable emission spectra, along with biocompatibility, have attracted great interest for fluorescence detection. Recent years, immune chromatography technology has great success as a rapid diagnosis technique in biology and medicine and spread to food safety detection. Based on the excellent fluorescence properties of quantum dots, we tried to integrate immune chromatography with quantum dots to construct immunochromatographic test paper, using for the detection of Escherichia coli O157:H7 in food.The paper focused on the quantum dots immunochromatographic system, mainly as follows:1. Using Te powder and CdCl2 as precursor, thioglycolic acid as modifier synthetize CdTe quantum dots. Test the relevant properties of quantum dots in different solvents. Quantum dots size increased gradually in the synthesis process of reflow. Quantum dots stabilized at pH4-13 and aggregated at extremely acid or alkaline conditions. Quantum dots were stable in salt and alcohol system. Compared purification effect of three different kinds of organic solvents on quantum dots and the best quantum dots purification method was using acetone.2. To study the changes of the fluorescence spectra of quantum dots in different preservation conditions, it was found that quantum dots have growth and change in the preservation process, enhanced fluorescence properties. Temperature greatly influences the growth of quantum dots, the basic stability properties preserved under low temperature condition. With light and oxygen, photo oxidation was happened, so the surface of CdTe was coated with CdS, promoted its particle size and enhances the fluorescence. This method can be used to reduce the surface defects of QDs and made the QDs had better fluorescence properties. To keep the stable properties of quantum dots, low temperature, avoiding light and the sealing was the best strategy.3. Red CdTe quantum dots and Escherichia coli O157:H7 antibodies were used as the research objection. By the electrostatic coupling and EDC coupling method for coupling of CdTe quantum dots and Escherichia coli O157:H7 antibody, and by immunohistochemistry assay to verify the coupling effect. The results show that the electrostatic coupling method in pH 7.2 is the best coupling method. EDC caused QDs quenching in the implementation process, so this method is lack of practical significance.4. Escherichia coli O157:H7 antibody and Goat anti Rabbit IgG were fixed on the chromatography membrane. Quantum dots monoclonal antibody conjugations infiltrated on combination pad and dry it. Constructed the immune chromatography system and detected Escherichia coli O157:H7. The specificity of the test paper was very well, the minimum detection limit is 104CFU/mL, the detection time is less than 5min, but need portable ultraviolet light observation. Quantum dots fluorescence immunochromatographic detection in real samples can exclude the interference of the food itself, can reduce the difficulty of the pretreatment of the sample to be detected, by which the detection sensitivity was enhanced. |
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