The Spectral Analysis Of Gold Nanoparticles And Aptamers And Its Application In Protein’s Detection

Gold nanoparticles are widely applied in analytical chemistry due to theirs uniquesurface effect, high catalytic properties, dielectric effect and fluorescence effect.Aptamers are single-stranded DNA or RNA sequences, highly specific binding to thetarget substance, and can be adsorbed onto the surface of gold nanoparticles. The goldnanoparticles-aptamers probe system can be used in the detection of varioussubstances and ions.In this thesis, the spectral properties of gold nanoparticles andaptamers and its applications in protein detection have been studied. The maincontents include the following parts:(1) Gold nanoparticles were prepared according to the reported Frens with a slightmodification. The gold nanoparticles’ size and concentration were detected byUV-visible spectrophotometry. Firstly, the single-strand DNA-aptamers of adenosinewere absorbed to the surface of the gold nanoparticles. When adding adenosine intothe solution, the adenosine hybridized with theirs aptamers in the pH7.4Tris-HClbuffer system. Then the gold nanoparticles aggregated causing by NaCl, which canchange theirs UV-visible spectrum. At the same time, the color of the solutionchangeed from red to blue. In this way we can detect the content of adenosineindirectly.(2) The synthesized gold nanoparticles are characterized by UV-visiblespectrophotometry for the particle size and colloid concentration.The single-strandDNA-aptamers sequences of thrombin were absorbed to the surface of the goldnanoparticles.Then added thrombin into the solution. After thrombin hybridized withtheirs aptamers, gold nanoparticles aggregated causeing by NaCl, which can enhancethe fluorescein’s fluorescence signal. Since the aggregated gold nanoparticles anddispersed gold nanoparticles have different influence to the fluorescein’s fluorescence,we can detect the content of thrombin through the fluorescence of the fluorescein.(3) The isoelectric point of human IgG is7.5-7.8.When the solution pH is greaterthan7.8, the human IgG with a negative charge and the solution does not causeaggregation of gold nanoparticles.While the solution pH less than7.5, the human IgGwith a positive charge and can cause gold nanoparticles aggregated. Dispersed goldnanoparticles’ UV-visible absorption maximum at527nm, while entirely aggregatedgold nanoparticles’ UV-visible absorption maximum shifted to765nm. The UV- visible absorption ratio, ie A527/A765can be used as a measure of the degree ofaggregation of gold nanoparticles, which can quantitatively detect human IgG.