Development of a two-in-one integrated bioassay for simultaneous and rapid on-site detection of Pb and Hg in water.

Exposure to heavy metal pollution represents a serious health risk and requires rapid, sensitive, and accurate detection to protect human health. However, the existing methods had various limitations for simultaneous detection of heavy metals. Herein, a novel two-in-one integrated bioassay was constructed for simultaneous on-site determination of Hg and Pb through combining all-fiber bicolor fluorescence biosensor (ABFB), functional nucleic acids (FNAs), and FRET. Hg biosensor, consisting of BQ-T14 and CY-A14, performed its detection based on specifical binding of Hg and T bases to form T-Hg-T mismatch structure. GR-5 DNAzyme, consisting of GR-5S and GR-5E, is applied for Pb biosensor. The higher concentration of Hg and Pb results in the more T-Hg-T mismatch structure formed and the GR-5E to cleave the more GR-5S, respectively, thus allowing higher detectable fluorescence intensities in two signal channels. Thanks to high selectivity of two FNAs-biosensors and excellent time-resolved effect of the ABFB, the Hg and Pb could be directly and simultaneously quantitated in 12 min, and had the LODs of 4.22 nM and 1.55 nM, respectively. The satisfied recovery rate of real samples was verified by ICP-OES. Our strategy could serve as a simple and cost-effective on-site high-frequency detection of heavy metal ions.