One-pot enzyme-free amplified detection of trace mercury contamination in aquatic products using mid-toehold-mediated-DNA Strand displacement

Mercury pollution in aquatic products poses critical risks due to bioaccumulation and biomagnification in the food chain, necessitating tools for rapid, sensitive and accurate detection of mercury in food samples. Herein, we developed a mix-and-read, enzyme-free amplified method for one-pot detection of mercury pollution in aquatic products based on mid-toehold mediated- DNA strand displacement reaction. The key innovation of the method lies in the design of a pre-quenched T-rich duplex probe that enables Hg²⁺-activated strand displacement through T-Hg²⁺-T coordination, releasing two fluorophores per binding event to achieve intrinsic signal amplification. This design achieved a detection limit of 4.17 nM with 5.9-fold enhanced sensitivity via the amplification, and allowed to complete Hg²⁺ quantification within 30 min. Validation in shrimp and salmon yielded 85.70–104.38 % recoveries, shows high accuracy for detecting mercury in food samples. The enzyme-free amplified assay can serve as an efficient tool for monitoring mercury contamination in aquatic products.