A novel molecular logic system based on lead-induced substitution of potassium from a G-quadruplex as a fluorescent lead sensor

Abstract

A label-free molecular logic system is developed based on a G-quadruplex conformation change, which can be reported using a small dye molecule N-methyl mesoporphyrin IX (NMM) as the fluorescent signaling indicator. In the absence of Pb²⁺, the K⁺-stabilized G-quadruplex could bind with NMM, resulting in strong fluorescent intensity. In contrast, the fluorescence decreases greatly when Pb²⁺ is present. This molecular logic system provides a simple biosensor for Pb²⁺. The biosensor has shown high accuracy, selectivity, and sensitivity, as well as linearity within a wide concentration range with a detection limit of 5 nM, which meets the EPA standard for Pb²⁺ (50 nM).