A selective amperometric sensing platform for lead based on target-induced strand release

Abstract

A novel strategy for selective and sensitive amperometric detection of lead ion (Pb²⁺) was proposed based on target-induced strand release. The underlying gold electrode was pre-modified with dendritic gold nanoparticles by direct electrodeposition to afford increased electrode surface area for immobilization of thiol group-containing capture DNA molecules. The hybridization of the capture DNA molecules with Pb²⁺-specific aptamer molecules to form a DNA duplex, into which methylene blue was intercalated, induced measurable electrochemical signal. Upon addition of Pb²⁺, it could specifically bind to its aptamer to form Pb²⁺-stablized G-quadruplex and induce the aptamer strand to release from the electrode surface into solution, accompanied by the release of intercalated MB responsible for significant signal reduction. The fabricated biosensor showed a linear response to the logarithm of Pb²⁺ concentration over the range of 1.0 × 10⁻¹⁰ M to 1.0 × 10⁻⁷ M with a detection limit of 7.5 × 10⁻¹¹ M. In addition, this strategy afforded an exquisite selectivity for Pb²⁺ against other metal ions. The excellent sensitivity and selectivity show good potential for Pb²⁺ detection in real environmental samples.