Gold Nanoparticles Based Visual Analysis For Quinidine And Potassium Ions Detection

Gold nanoparticles have been widely used in biochemical analysis as an excellent optical probe. Detections based on the changes of AuNPs’physical and chemical properties have realized the analysis of various objects. Among these methods, the change of the AuNPs’localized surface plasmon absorbance (LSPR) has been developed ripely, and the application of gold nanoparticles-based enzyme mimics has attracted considerable attentions. Both of the above methods could be used to realize visual analysis simultaneously. In this paper, we focused on these properties of gold nanoparticles and developed visual analysis for medical molecule and metal ion detections. Details are listed as follows:1. Because of the localized surface plasmon resonance, the colloid solution of gold nanoparticles appears intense color. In particular, the aggregated nanoparticles solution shows a different color from the well dispersed one, which forms the basis of the visual analysis. It was found that quinidine could induce the aggregation of FSN-AuNPs, leading to the color of colloidal solution turned from red to purple then to blue, and the color information of each solution could be transformed into digital information with tricolor (RGB) system. Under the optimum conditions, the R value of the solution was found to be linear with the natural logarithm of concentration of quinidine in the range of112-384nmol/L. Compared with the traditional UV-Vis spectrophotometric method, our proposed method showed the same analytical ability for quinidine detection with the advantages of rapidness. low cost and simplicity, which can serve as an assistant method for practical use.2. Gold nanoparticles possess peroxidase-like activity, thus can catalyze oxidation of the peroxidase substrate3,3",5.5’-tetramethylbenzidine (TMB) to develop a blue color in the present of H2O2, and shows a maximum absorbance at650nm. It was found that the peroxidase activity of AuNPs could be greatly enhaced after capped with ssDNA. Then we took aptamer for potassium ions (K+) as an example. When the K+aptamer was adsorbed on the surface, AuNPs possese strong peroxidase activity. While upon the addition of K+, the aptamer folded into tetraplex structure (G-4) and detached from AuNPs, then the peroxidase activity of AuNPs reduced correspondingly, with a decrease in absorbance at650nm and a color fade. The change of absorbance at650nm (ΔA650) was found to be linear with the natural logarithm of concentration of K+in the range of1.5×10-4～2.8×10-3mol/L, r=0.9916. Compared with other metal ions, this method shows a good selectivity for K+. It also could be used for the detection of any targets that has a ssDNA aptamer.