Highly Sensitive and Selective Colorimetric Detection of Methylmercury Based on DNA Functionalized Gold Nanoparticles

A new colorimetric detection of methylmercury (CH₃Hg⁺) was developed, which was based on the surface deposition of Hg enhancing the catalytic activity of gold nanoparticles (AuNPs). The AuNPs were functionalized with a specific DNA strand (H_T7) recognizing CH₃Hg⁺, which was used to capture and separate CH₃Hg⁺ by centrifugation. It was found that the CH₃Hg⁺ reduction resulted in the deposition of Hg onto the surface of AuNPs. As a result, the catalytic activity of the AuNPs toward the chromogenic reaction of 3,3,5,5-tetramethylbenzidine (TMB)-H₂O₂ was remarkably enhanced. Under optimal conditions, a limit of detection of 5.0 nM was obtained for CH₃Hg⁺ with a linear range of 10⁻200 nM. We demonstrated that the colorimetric method was fairly simple with a low cost and can be conveniently applied to CH₃Hg⁺ detection in environmental samples.