The Surface Modification Of Luminescence And Magnetic Nano-Crystalline And Their Application In Clinical Detection

Tumor markers in serum can be used as an important standard of diagnosing. However, most of the usual methods are time-consuming, labor-intensive, and hazardous to health or require highly qualified personnel and sophisticated instrumentation. Therefore, there must be novel and excellent method for the rapid and inexpensive diagnosis of diseases.Semiconductor nanocrystals quantum dots （QDs） have attracted wide interest due to their various beneficial factors, which makes them advantageous over the convenient dyes, and more suitable for the usage in biology and medicine. Meanwhile, magnetic nanoparticles have been thoroughly studied due to their widespread biomedical applications. In the present research, the two nanomaterials were applied to develop a novel, quick and exact clinical kit by making use of the advantages of the both nanomaterials, and the details were as follows:Firstly, CdTe QDs were synthesized in aqueous phase, and the preparation precedure was optimized. The preparation of CdTe occurred in the aqueous phase by using thioglycolic acid as stabilizer. The influence of reflux time, pH of precursor, the mole ratio of precursors and storage time was investigated respectively to obtain the optimum reaction conditions.Secondly, The CdTe QDs were conjugated with the BSA through covalent binding, and then the photoluminescence （PL） intensity of CdTe QDs was measured compared with the no labeling one. The conjugation was confirmed by Gel electrophoresis （SDS and Native）. Meanwhile, the pH of system, reaction time and the mounts of coupling agents were optimized. As a result, the fluorescent complex was appropriate to be used as a protein probe to label antibody.Thirdly, Fe₃O₄ magnetic nanoparticles with good paramagnetism were prepared, and then Fe₃O₄ with shell of SiO₂ were obtained by the gel-gol method. Their monodispersity and structure were checked by using transmission electron microscope and X-ray diffraction, respectively. Next, the nanoparticles were modified byγ-Glycidoxypropyltrimethoxysilane （GMPS） to obtain active epoxy groups on the surface of nanoparticles.Fourthly, complex magnetic nanoparticles and IgG antibody were mixed and stirred overnight to coujugate amido with active epoxy groups by covalent binding. And then, the nanoparticles were scanned by FT-TR. Besides, the amount of antibody on the surface of magnetic nanoparticles was determined by the Brabford method. The result showed that about 8.11μg of IgG antibody was conjugated to the surface of 1 mg of Fe₃O₄/SiO₂, suggesting that there was enough IgG on the surface of each magnetic nanoparticle, which was the basis for subsequent preparation of sandwich composite.Finally, the calibration curve and the working equation were obtained. Based on the equation, the human serums were tested. The processes were: （1） the Fe₃O₄/SiO₂ nanoparticles were modified by GMPS and conjugated with mouse IgG antibody （the primary antibody）. And then the complexes of primary antibody and magnetic nanoparticles were used to capture the antigen, so as to separate them. （2） The water soluble fluorescent nanoparticles were synthesized and conjugated with mouse IgG antibody （the second antibody）. （3） The sandwich immunoreaction occurred, and the superfluous QDs-IgG antibody was washed away. The relationship between PL intensity of the complex and the concentration of AFP and CEA were determined, and the calibration equations, Y=1.30（X-8.30） and M=0.68（N-0.50）, were obtained. （4） The human serum samples of 10 people were tasted. The result showed that the outcomes determined by this method were similar to those determined by Elisa. The slight difference still existed and the reason may lie in that there were some molecules with the similar structure to antigens.Because of inevitable conditional restriction, the human serum could never be collected easily. So the pre-treatment of the serum should never be shook so as to reduce the interference caused by the protein molecules with the similar structure to antigens, when the proceeding research were carried out. In the meantime, the preparation of nanoparticles is to be further optimized. Through these ways, the CdTe QDs will have narrower half high, and Fe₃O₄/SiO₂ magnetic nanoparticles better paramagnetism.