Fe3O4/Au NPs-based electrochemical sensor for the detection of Hg ion in Traditional Chinese Medicine

Mercury ion (Hg 2+ ), a highly toxic and bioaccumulative pollutant, can contaminate medicinal herbs and pose significant risks to human health via the food chain. With the growing global demand for traditional Chinese medicine (TCM), there is an urgent need to develop reliable and sensitive Hg 2+ detection methods. In this paper, a novel electrochemical sensor based on magnetic nanoparticles and thymine-Hg 2+ -thymine (T-Hg 2+ -T) coordination chemistry was developed for detecting Hg 2+ in TCM. The magnetic Fe 3 O 4 /Au nanoparticles (Fe 3 O 4 /Au NPs) were synthesized and employed as carriers to conjugate with T-rich thiol-modified DNA probes. In the absence of Hg 2+ , the DNA probes hybridized with ferrocene (Fc)-labeled complementary DNA (cDNA), bringing the Fc signal molecules close to the Fe 3 O 4 /Au NPs surface. In the presence of Hg 2+ , these probes preferentially formed stable T-Hg 2+ -T complexes, effectively inhibiting cDNA hybridization. The Hg 2+ concentration was determined by measuring the corresponding changes in the Fc current. The sensor exhibited a good linear response to Hg 2+ in the range of 0.1–100 ng/mL, with a low detection limit of 0.08 ng/mL. Furthermore, the method was successfully applied to determine Hg 2+ in representative TCM matrices (Lotus leaf, Lonicera japonica , Angelica dahurica , and Houttuynia cordata Thunb.) with satisfactory recoveries (96.73 %−104.84 %). This indicates that the proposed method is particularly suitable for Hg 2+ determination in complex TCM samples, providing a practical solution for quality control and safety monitoring in TCM.