Development of a novel fluorescence light-up Pb²⁺ sensor using a G-quadruplex complex with modified thioflavin T

Here, we developed a novel, cost-effective fluorescence light-up biosensor for Pb²⁺ detection based on a label-free G-quadruplex combined with modified thioflavin T (ThT) derivatives. Among the various G-quadruplex sequences tested, only T2 exhibited fluorescence light-up properties upon interacting with the modified ThT derivatives in the presence of Pb²⁺. To enhance the Pb²⁺ sensing system, we also compared modified ThT derivatives, including the newly synthesized propyl-substituted ThT (ThT-P) and butyl-substituted ThT (ThT-B). Among the tested derivatives, ethyl-substituted ThT (ThT-E) exhibited the most significant fluorescence enhancement upon the addition of Pb²⁺. Our designed sensor demonstrated high selectivity and sensitivity for Pb²⁺, enabling practical applications, as validated through the successful detection of Pb²⁺ in spiked environmental water samples. We envision that our new strategy could be further developed into a versatile platform for the detection of a broad range of metal ions.