A novel label-free fluorescence assay for one-step sensitive detection of Hg in environmental drinking water samples.

A novel label-free fluorescence assay for detection of Hg was developed based on the Hg-binding single-stranded DNA (ssDNA) and SYBR Green I (SG I). Differences from other assays, the designed rich-thymine (T) ssDNA probe without fluorescent labelling can be rapidly formed a T-Hg-T complex and folded into a stable hairpin structure in the presence of Hg in environmental drinking water samples by facilitating fluorescence increase through intercalating with SG I in one-step. In the assay, the fluorescence signal can be directly obtained without additional incubation within 1 min. The dynamic quantitative working ranges was 5-1000 nM, the determination coefficients were satisfied by optimization of the reaction conditions. The lowest detection limit of Hg was 3 nM which is well below the standard of U.S. Environmental Protection Agency. This method was highly specific for detecting of Hg without being affected by other possible interfering ions from different background compositions of water samples. The recoveries of Hg spiked in these samples were 95.05-103.51%. The proposed method is more viable, low-costing and simple for operation in field detection than the other methods with great potentials, such as emergency disposal, environmental monitoring, surveillance and supporting of ecological risk assessment and management.