A GelRed-photosensitized electrochemical DNA biosensor based on DNA cleavage for Hg2+ detection in water

GelRed-photosensitized DNA cleavage enabled Hg 2+ detection. • T-Hg 2+ -T coordination triggered dsDNA assembly and GR intercalation. • The biosensor showed a linear range of 0.01–100 nM and an LOD of 1.30 pM. • Spiked water samples gave recoveries of 83.89–119.43%. A label-free GelRed-photosensitized electrochemical DNA biosensor was developed for Hg 2+ detection in water based on light-induced DNA cleavage. The sensing strategy integrates Hg 2+ -specific T-Hg 2+ -T coordination, GelRed (GR) intercalation, photosensitized oxidation, and impedance-based electrochemical readout. In the presence of Hg 2+ , two thymine-rich single-stranded DNA probes assemble into a double-stranded DNA structure through T-Hg 2+ -T coordination, allowing the nucleic acid dye GR to intercalate into the double-stranded DNA (dsDNA). Upon green-light irradiation, the dsDNA-GR complex acts as a photosensitizing system to generate singlet oxygen ( 1 O 2 ), which induces oxidative cleavage of the DNA and consequently changes the interfacial R ct . Under optimized conditions, R ct showed a linear relationship with the logarithm of Hg 2+ concentration, described by R ct (Ω) = −907 log C (Hg 2+ ) + 5312. The biosensor exhibited a linear range of 0.01–100 nM and a low limit of detection (LOD) of 1.30 pM. In spiked environmental water samples, recoveries of 83.89–119.43% were obtained with relative standard deviations of 3.49–9.32%, and the results were further evaluated by comparison with atomic fluorescence spectrometry. This work provides a GelRed-photosensitized DNA-cleavage strategy for sensitive and label-free electrochemical monitoring of Hg 2+ in aquatic environments. A label-free photocatalytic electrochemical DNA biosensor was developed for the detection of Hg 2+ in water. Download: Download high-res image (126KB) Download: Download full-size image