Manganese Modified CdTe/CdS Quantum Dots As An Immunoassay Biosensor For The Detection Of Golgi Protein-73

Quantum dots(QDs), compared with organic dyes, have unique and attractive fluorescence properties, such as high photoluminescence quantum yields, broad excitation and narrow/symmetry emission spectrum, resistance to photo-bleaching and large stokes shift. As new fluorescence probes, QDs have shown wide application prospects in the biological tissue imaging and immunoassay detection. However, in biological detection, the fluorescent signals of QDs can be affected by various interferents in the sample when detecting target protein and cannot be directly applied in immunoassay. Therefore, how to improve the specificity and sensitivity for the biological molecules detection using QDs as fluorescence probes remains to be a problem.In this dissertation, QDs were used to develop a new fluorescence bioprobe and ion exchange fluorescent signal amplification method. They were applied to the detection of golgi glycoprotein 73(GP73) and adenosine respectively in order to improve the sensitivity and specificity of the QDs deteciton in biological analysis.1. As a novel liver cancer diagnosis marker, GP73 has low expression in a normal liver, but is highly expressed in the chronic hepatitis, especially in the early hepatocellular carcinoma(HCC). Lots of studies have found that the sensitivity of GP73 is superior to another serum marker of liver cancer alpha-fetoprotein(AFP) for the early diagnosis of liver cancer. Only the enzyme-linked immunosorbent assay method is applied to the GP73 quantitative assay in the clinical test. However, this method needs complicated manipulation procedures and long analysis time. Therefore it is very important to establish a rapid and simple method for the detection of serumGP73. In this research paper, Mn modified Cd Te/Cd S QDs were covalently conjugated with GP73 Ab, and then the protein A/G agarose beads were specifically combined with the QDs-conjugated Ab, which facilitated the separation step. The QDs-Ab-beads immunocomplex was used for the detection of GP73 antigen in serum samples. Based on the fluorescence quenching of the QDs-Ab-beads bioprobe by GP73, a simple、rapid and low-cost method for GP73 determination was proposed.Under the optimum conditions, the quenched intensity of the fluorescence versus GP73 concentration from 20 to 150 ng m L-1 gave a linear response with an excellent correlation coefficient of 0.9935, and the limit of detection(3?/K) was 10 ng m L-1.2. QDs are beneficial to amplify the detection signal and improve the detection sensitivity for ultrasensitive detection due to their metal components and high divalent cation content levels. In this research paper, novel fluorescence signal amplification via cation exchange reaction in QDs was developed. We used TBF1-conjugated Fe3O4 as separation medium and TBF2-conjugated Cd Te QDs as detection probes for efficient separation and highly sensitive detection in the presence of the target. After magnetic separation, excess Ag+ ions was added to release a large number of Cd2+ ions inside Cd Te QDs. Ag Te is more thermodynamically favored compared with Cd Te,and thus Ag+ ions will therefore readily exchange Cd2+ ions. After magnetic separation, the amounts of surplus Ag+ in the supernatant could be detected by Cd Te QDs. Because Ag+ could quench the fluorescence, the fluorescence of added QDs had a liner relation with the concentrations of the target. We developed a simple, rapid and efficient signal amplification method and did not need use other expensive fluorescence detecting probe. This method was applied to detect adenosine and achieved good results.