Aptasensor based on cascaded fluorescent sensor assisted by exonuclease III for ultra-sensitive detection of Hg²⁺

Construct a sensitive and rapid detection fluorescence biosensor with the assistance of exonuclease III to achieve efficient detection of Hg²⁺. Nucleic acid aptamer H0 specifically recognizes Hg²⁺, and under the action of exonuclease III, H0 bound to Hg²⁺ is hydrolyzed, which in turn fails to trigger the catalytic hairpin self-assembly amplification reaction, resulting in a decrease in the number of double-stranded DNA bound to the fluorescent dye SYBR Green I in the solution, and a decrease in the fluorescence intensity. The results showed that the concentration of Hg²⁺ showed a good linear relationship with the fluorescence intensity of the sensing system within the range of 3.8–10 pmol/L, and the detection limit was 0.53 pmol/L. The recoveries of Xiangjiang River water used for the analysis of the actual samples were in the range of 99.57–103.58%, and the relative standard deviations of the determined values were 2.4–3.7%. The method is simple, sensitive, specific, cost-effective and can be applied to water samples.