Abstract：Silver is widely used in medical materials, photography, electronics, imaging and other industries because of its unique properties. However, silver ions are listed as one of the most toxic heavy metal ions, which poses a serious threat to the environment and human health. In order to detect the concentration of silver ions in an aqueous environment sensitively and accurately, a fluorescence aptasensor for detecting the concentration of silver ions in aqueous environment is proposed, which takes advantage of the excellent optical quenching property of nanogold and the stronger ability of double chain aptamers to capture silver ions based on the principle of fluorescence energy resonance transfer. Aptamer modified with SH bonds were mixed with nanogold to form stable nanostructures, and aptamer labeled with FAM were added to form a working solution to detect the concentration of silver ions. In the absence of silvers, two aptamers cannot hybridize with each other due to the repulsive force between the mismatched bases C—C, and the reaction system has strong fluorescence. In the presence of silver ions, the mismatched C—C in the double-stranded aptamers can form a stable C—Ag+—C base pair with the silver ions through the interaction between metal ion and base. The generation of this composite structure will shorten the distance between the gold nanoparticles and the fluorophore, so that the fluorescence signal will gradually weaken with the increase of silver ion concentration. According to the change of fluorescence intensity before and after adding silver ion, the concentration of silver ion can be detected. At the same time, in order to improve the sensitivity and stability of the sensor, the concentration ratio of gold and nucleic acid aptamers in the working solution, the concentration of sodium chloride, the pH of the buffer and the culture temperature were optimized. The results showed that when the volume ratio of 0.012 5 g·L-1 nano gold to 5 μmol·L-1 aptamer was 5∶1, the concentration of NaCl was 260 mmol·L-1, the pH of the buffer was 7, and the culture temperature was 30 ℃, the initial fluorescence intensity of the working solution was the strongest, the detection limit of silver ion was 10 nmol·L-1, and the correlation coefficient was R2=0.99. Based on the characteristics of high recognition ability and strong affinity of aptamers to silver ions, the sensor showed good selectivity to silver ions and was not disturbed by other substances. In addition, the sensor has good specificity for silver ion concentration detection, and has the advantages of simple operation, sensitivity and no introduction of toxic solvents, so it has a good application prospect for silver ion concentration detection in the water environment.
Key words：Fluorescence aptasensor; Silver ion concentration; Fluorescence energy resonance transfer; Nano gold
[1] Gao X, Lu Y, Zhang R, et al. Journal of Materials Chemistry C, 2015, 3(10): 2302.
[2] Jan A, Azam M, Siddiqui K, et al. International Journal of Molecular Sciences, 2015, 16(12): 29592.
[3] Ndung’u K, Ranville M A, Franks R P, et al. Marine Chemistry, 2006, 98(2-4): 109.
[4] Yang X, Jia Z, Yang X, et al. Saudi Journal of Biological Sciences, 2017, 24(3): 589.
[5] Karandashev V K, Shishlina N I, Khvostikov V A, et al. Journal of Analytical Chemistry, 2019, 74(11): 1104.
[6] Xu Y, Zhang C, Du H, et al. Microchimica Acta, 2019, 186(8): 522.
[7] Kleinke K, Saran R, Liu J. Sensors, 2016, 16(9): 1370.
[8] Zhan S, Xu H, Zhan X, et al. Microchimica Acta, 2015, 182(7-8): 1411.
[9] Ebrahimi M, Raoof J B, Ojani R. Talanta, 2015, 144: 619.
[10] Long Q, Wen Y, Li H, et al. Journal of fluorescence, 2017, 27(1): 205.
[11] Lu Y, Meng L, Gao Y, et al. Analytical biochemistry, 2018, 549: 21.
[12] Qin W W, Dou W, Leen V, et al. RSC Advances, 2016, 6(10): 7806.
[13] Sui N, Wang L, Yan T, et al. Sensors and Actuators B: Chemical, 2014, 202: 1148.
[14] Zhu Y F, Wang Y S, Zhou B, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2018, 189: 190.
[15] Mao K, Wu Z, Chen Y, et al. Talanta, 2015, 132: 658.
[16] Wang G, Lu Y, Yan C, et al. Sensors and Actuators B: Chemical, 2015, 211: 1.
[17] Liu B, Liu J. Analytical Methods, 2017, 9(18): 2633.
[18] Wang G, Shao C, Yan C, et al. Journal of Luminescence, 2019, 210: 21.
[19] Lavis L D, Rutkoski T J, Raines R T. Analytical Chemistry, 2007, 79(17): 6775.
