Detection of Pb²⁺ in Aqueous Solution by Using a DNA-modified Microcantilever

We developed a novel Pb²⁺-sensor based on a microcantilever that was modified with a specific Pb²⁺-dependent DNAzyme molecule. This microcantilever sensor could detect Pb²⁺ sensitively and selectively in an aqueous solution. Upon complexation with Pb²⁺, the DNAzyme duplex unwinded and formed a G-quadruplex conformation, which led to an increase of repulsion between the DNAzyme molecules and a subsequent bending of the microcantilever. This microcantilever sensor could be regenerated, flowing through a strong Pb²⁺ chelator, 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid. The detection limit of the microcantilever sensor for Pb²⁺ ions is as low as 10^-8 M. The microcantilever sensor also exhibited a high selectivity to Pb²⁺ over other metal ions such as Mg²⁺, Fe³⁺, Zn²⁺, Ca²⁺, and Cd²⁺.