Practical, highly sensitive, and regenerable evanescent-wave biosensor for detection of Hg2+ and Pb2+ in water

A “turn-on” evanescent-wave fiber biosensor based on functional nucleic acids was developed for on-site detection of Hg2+ and Pb2+ in environmental water samples. A two-step strategy was conducted to take advantage of the rapid binding of T–T mismatches with Hg2+ and the cleavage of a substrate by 8–17 DNAzyme with Pb2+ in solution, as well as sensitive DNA detection on a liquid–solid interface based on evanescent wave. The biosensor demonstrated high sensitivity (with a detection limit of 22 pM for Hg2+ and 20 nM for Pb2+) and selectivity without any signal amplification, rapid detection (within 13 min per test), low cost (10–20 Chinese yuan per sample), and multiple-cycle regeneration (at least 18 times). The method was also successfully applied on Hg2+ and Pb2+ detection in real environmental water samples.