The Development Of Novel Methods For Rapid Detection Of Mercury Ion Based On Membrane Technology

Mercury ion (Hg2+) is one of the most toxic and dangerous heavy metals that can have adverse effect on human health, food and environmental safety. Detection of mercury ions is usually highly depended on instruments. However, these methods are not only time-consuming and expensive but also difficult to meet the needs of urgent detection requirements. It greatly limits the wide applications of these methods. In order to realize the detection of mercury ion quickly and conveniently, two kinds of membrane based methods including the signal amplified nucleic acid lateral flow strip method and nucleic acid array method were developed for rapid detection of mercury ions.(1) Signal amplified nucleic acid lateral flow stripSignal amplified nucleic acid lateral flow strip (SA-LFS) is proposed for direct ultrasensitive and on-site detection of Hg2+based on the specific recognition system of thymine-Hg2+-thymine using gold nanoparticles (AuNPs) as the labeling tags. The signal was further amplified by hybridization induced dual labeling of AuNPs, increasing the signal intensity of test line on strips. The presence of both probes on the LFS enabled both sensing and signal amplification achieved in a single step. The fabricated SA-LFS is capable of rapid and ultrasensitive detection of Hg2+with LODs of 0.005 ppb and 0.0015 ppb by visual observation and quantitative analysis, respectively. At least 40-fold improvement in sensitivity was achieved through this signal amplification treatment. The successful application of the developed method in rapid sensing of mercury ions in spiked water samples was also conducted to confirm the practical utilization of this signal amplified LFS.(2) Nucleic acid array based methodThe main sensing principle of nucleic acid array based method is using the T-Hg2+-T recognition system. One of recognition probe as the capture probe is immobilized on the nitrocellulose membrane. The other probe is immobilized on the surface of gold nanoparticles by Au-S bond. For detection of mercury ions, the two probes would hybridize with each other through the formation of T-Hg-T structure, inducing the immobilization of gold nanoparticles on the NC membrane. The limit detection of is 0.5 ppb by perusal. The detection limit of the proposed method is 0.5 ppb with naked-eye observation. Furthermore, silver staining operation was carried out to increase the sensing signal taking advantage of the catalytic effect of the captured gold nanoparticles. Using this signal amplification treatment,0.001 ppb as the detection limit is achieved and at least 500-fold improvement is realized for ultrasensitive and rapid detection of mercury ions. Then, silver staining enhances the signal because of the catalytic effect of gold nanoparticles, and the limit of detection is 0.001 ppb which has been improved 500 times by naked eye observation.