Development Of Fluorescent And Electrophoretic Assays For Gold Nanoparticles And Their DNA Conjugates

Gold particles with nano-scale had many special properties such as quantum size effects, surface effects, optical effects and compatibility effects. With these properties, gold nanoparticles and their bioconjugates were widely used in clinical diagnostics. At the present time, characterization of gold nanoparticles and their DNA conjugates are being relied on TEM, fluorescence quenching and other techniques. But the equipments and operations are so expensive and complicated that economical and simple methods need to be developed.In this thesis, new characterizing methods for gold nanoparticles and their DNA conjugates have been developed with fluorescent and electrophoretic assays which have been regularly used in most laboratories. For the fluorescent assay, fluorescence enhancement was observed when adding gold nanoparticles to the fluorescein solution. Gold nanoparticles with different sizes could enhance the quantum yields 3-10 times in fluorescein solution without any further optimization, and the same phenomenon was discovered in aminomethyl pyrene solution, higher enhancement results was obtained in aminomethyl pyrene solution compared to fluorescein solution. When increase the concentration of gold nanoparticles, fluorescence quenching was observed. With these fluorescence enhancement techniques, the LLD of biomolecular detection could be improved greatly.Moreover, capillary electrophoresis was established for the separation of gold nanoparticles and modified gold nanoparticles. Electrophoretic injections was conducted at 20Kv for 20s, and separation was carried out at 15Kv, Capillary is 75cm long (50cm to the detector) fused-silica capillary with 365μm OD and 75μm ID, we could separate the colloidal gold with different diameters. Further experiments need to be developed to get better results. On the other hand, it is already found that gold nanoparticles could be separated under gel electrophoresis. Gel electrophoresis has electrostatic effects and molecule sieving effects so it's could split Au nanoparticles with different sizes precisely. Under these conditions, small particles have large electrophoresis mobility. Moreover it was found that the modified gold nanoparticles'electrophoresis mobility is differing from the unmodified. Small particles are determined to be optimal size for the surface modification and it could maximally increases the sensitivity of the DNA detection.