Fluorescent biosensor for lead ion detection based on GR-5 DNAzyme and self-hybridization chain reaction

Lead ion (Pb²⁺) is a typical heavy metal pollutant, and the water and food contaminated by lead may pose a potential threat to the environment and human health. In the natural environment, it can accumulate in soil and water, affecting the entire food chain. For human health, even if the Pb²⁺ content is very low, it can cause a series of adverse health effects. In order to effectively address the issue of lead pollution, it is particularly important to develop highly sensitive and selective Pb²⁺ detection technology.

In this study, we designed a single-hairpin based self-hybridization chain reaction (SHCR) system for Pb²⁺ detection based on GR-5 DNAzyme. Compared with the traditional hybridization chain reaction (HCR) which requires two hairpins, this strategy only needs one hairpin probe, this design not only reduces the experimental cost, but also simplifies the sequence design and experimental operation. Once Pb²⁺ was added in the system, GR-5 DNAzyme can be actived and then a trigger DNA was released to trigger the SHCR reaction, thereby a signal-amplified fluorescent biosensor for Pb²⁺ detection was developed, which exhibited a good linear range from 100 to 500 nM with a low detection limit of 24.8 nM, and has been successfully applied to the determination of Pb²⁺ in environmental water and Chinese Baijiu.

This simple, sensitive, and selective Pb²⁺ detection system demonstrates significant potential for a wide range of practical applications in both environment and food monitoring. In addition to its specific application for Pb²⁺ detection, by introducing different DNAzymes, this SHCR system can be applied for the detection of other heavy metal ions.