Study On A Novel Rapid Immnunoassay Of Milk Allergen Based On Double Labelling Immune Probe Of Gold Mag-quantum Dots

In recent years, with the improvement of people’s living standards and the widespread of dairy products, milk allergy has been widespread concern. In this paper, quantum dots(QDs) with good optical property combined with goldmag nanoparticles(Fe3O4/Au) which can be quickly enriched, and a double-probes system composed of Fe3O4/Au nanoparticles and QDs of milk allergen rapid detection was established. The main work was carried out as following:1. Water-soluble Cd Te quantum dots which show green、yellow、orange、and red fluorescence, respectively, were prepared in aqueous solution using 3-mercaptopropionic acid as the stabilizer. Amino-functionalized Fe3O4-PEI composites synthesized by the one-pot solvothermal method were then modified with Au nanoparticles twice to get the multi-layer structure Fe3O4/Au composites. The results showed that these quantum dots had good optical properties, wide and continuous excitation spectrum, narrow and symmetric emission spectra, high quantum yields and difficult coagulation. Besides, the goldmag nanoparticles also had uniform particle size, good dispersion, good crystal structure and magnetic properties, which could be used for magnetic separation and biological modification. It would provide a guarantee for the following development and application.2. The orange-emitting Cd Te QDs, mouse Ig G, goat-anti-mouse Ig G and rabbitanti-mouse Ig G were taken as the representative to establish the rapid immnunoassay based on double labelling immune probe of Gold Mag-quantum dots. Besides, the synthesis conditions of the two probes were optimize. Among them, rabbit-anti-mouse Ig G were coupled with Fe3O4/Au composites to form the goldmag probes, and goatanti-mouse Ig G were coupled with Cd Te QDs to form the fluorescent probe. Goldmag probes, mouse Ig G and fluorescent probe were combined to form a "sandwich" complexes eventually. According to the fluorescence intensity of the complex, quantitative detection of mouse Ig G was accomplished. The results showed that the amount of mouse Ig G was positively correlated with the fluorescence signal under the optimized conditions. It showed the rapid immnunoassay based on double labelling immune probe of Gold Mag-quantum dots was successfully established, and could be used in detecting the actual samples.3. On the basis of the previous studies, two kinds of anti-casein antibodies with different sites of action were used in this research. Mc Abs(monoclonal antibodies) were combined with Fe3O4/Au composites as the capture probes, and Pc Abs(polyclonal antibodies) were combined with Cd Te QDs as fluorescent detection probes. A new "sandwich" immunoassay of casein was established, and used in the actual testing for milk. It was found that there was a good linear tendency between casein concentration and the fluorescence intensity in the measured range of 6.25-100 ng/m L, and the lowest detection limit(LOD) was 1.8 ng/m L. Thus, it will provide important theoretical value and practical significance in the detection of milk allergens.