Practical aptamer-based assay of heavy metal mercury ion in contaminated environmental samples: convenience and sensitivity

Due to heavy metals’ magnified pollution from their accumulation in the ecosystem, practical detection of ultra-low concentration of heavy metals in environmental sample is of great significance for environmental supervision and maintenance of people’s health. Herein, a practical and sensitive assay of heavy metal mercury was developed by visually observing (or spectrum detecting) the change of cationic gold nanoparticles (AuNPs), which is directly caused by mercury ion induced hybridization between non-canonical base pairs. In this assay, signal probe’s response was direct rather than the indirect salt induction, thus avoiding the defect of salt-induced indirect response. It makes the analysis more sensitive. The results showed that the response of 8.2 × 10−8 M Hg2+ could be observed with naked eye and the detection limit of Hg2+ in spectrometric determination was 4.9 × 10−11 M, which is more than one order of magnitude lower than that from indirect response pattern of signal probe. In addition, high specificity of the affinity chemistry for T–Hg–T renders the assay to be highly selective. Compared with the results of cold vapor atom adsorption spectroscopy (CVAAS), this analysis has good reliability for the detection of mercury. The results fully indicate that the developed assay is an ideal alternative for online detection of heavy metal mercury in environmental pollution samples.