Electrophoretic Characterization Of Gold Nanoprobes And Its Application On Detection

Gold nanopartilces have many special properties such as quantum size effects,suface effects,Optical effects and compatibility effects.With these properties,gold nanoparticles and their bioconjugates were widely used in clinical diagnostics and material field.At present,characterization of gold nanoparticles and their DNA conjugates are being relied on TEM 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, mixed monolayer protected nucleic acid gold nanoprobes were prepared by modifying gold nanoparticles with both DNA and 4-mercaptobenzoic acid(MBA) or DNA and mercaptohexanol(MCH). Agarose gel electrophoresis, capillary electrophoresis and fluorescence quenching were used to characterize the gold nanoprobes. Gel electrophoresis testing results showed that 2% is proper for our experiment.The smaller the size is,the electrophoretic mobility quicker.The more DNA will cause the slower electrophoretic mobility.With the incresement of MCH,the electrophoretic mobility slower and then quicker. With the incresement of MBA,the electrophoretic mobility becoming quicker.MBA–DNA monolayers on gold nanoparticles is more stable than MCH-DNA monolayers on gold nanoparticles and DNA replacing MBA is easier than MBA replacing DNA. Capillary electrophoresis testing results showed that the mixture of the two gold nanoprobes(modifying gold nanoparticles with DNA and MBA)can't separate by capillary electrophoresis but can separate by capillary gel electrophoresis.Our thesis found that fluorescence enhancement was observed when adding gold nanoparticles to the fluorescein solution.Gold nanoparticles with different size can 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.At present, fluorescence quenching extensively used in the detection of DNA or protein. On the one hand our article discussed the effect of the DNA length and particle size on the fluorescence quenching,on the other hand,detection DNA based on fluorescence quenching,and the limitation is 3nM-5nM.