Specifically and Visually Detect Methyl-Mercury and Ethyl-Mercury in Fish Sample Based on DNA-Templated Alloy Ag-Au Nanoparticles.

Methyl-mercury (CHHg) and ethyl-mercury (CHHg) have much higher toxicity than Hg and can be more easily accumulated by organisms to form severe bioamplification. Hence, the specific and on-site detection of CHHg and CHHg in seafood is of great significance and a hard challenge. We herein designed two T-rich aptamers (H and H) for specifically recognizing CHHg and the total of CHHg and CHHg, respectively. In the presence of all Au, Ag, and T-rich aptamer, CHHg and CHHg specifically and preferentially bind with aptamer and thus induced the formation of alloy Ag-Au nanoparticles after reduction, which led to the color change in solution. This provided a sensing platform for the instrument-free visual discrimination and detection of CHHg and CHHg. By using H as probe, the method can be used to detect as low as 5.0 μM (equivalent to 1.0 μg Hg/g) of CHHg by bare eye observation and 0.5 μM (equivalent to 100 ng Hg/g) of CHHg by UV-visible spectrometry. By using H as probe, the method can be used to detect the total concentration of CHHg and CHHg with a visual detection limit of 5.0 μM (equivalent to 1.0 μg Hg/g) and a UV-visible spectrometry detection limit of 0.6 μM (equivalent to 120 ng Hg/g). The proposed method has been successfully used to detect CHHg and CHHg in fish muscle samples with a recovery of 101-109% and a RSD ( n = 6) < 8%. The success of this study provided a potential method for the specific and on-site detection of CHHg and CHHg in seafood by only bare eye observation.