DNA-mediated charge neutralization of AuNPs for colorimetric sensing of Hg2+ in environmental waters and cosmetics

Abstract

Mercury (Hg) is an important environmental pollutant because of its high toxicity. With the rapid industrialization, on-site monitoring Hg2+ contamination becomes increasingly important. In this work, a facile colorimetric sensing system based on DNA-mediated charge neutralization of AuNPs as well as smartphone data acquisition was developed for on-site monitoring of Hg2+. The designed both-end block dsDNA system (probe DNA and block DNA) can interact with the replacement DNA and formed T-Hg2+-T mismatched dsDNA in the presence of Hg2+, thus releasing the long block DNA as well as preventing the ThT-induced neutralization of AuNPs. The color change for the AuNPs neutralization can be pictured and analyzed by a portable smartphone. This on-site Hg2+ monitoring system was quite simple and sensitive with a low limit of detection (2.8 nM), lower than the maximum permitted amount of Hg2+ in drinking water regulated by EPA. The accuracy of the proposed method was verified through analysis of two certified water samples, four real water samples and seven cosmetic samples, and the results agreed well with the certified values or those by atomic fluorescence spectrometry. Overall, this facile and simple sensing system is an appealing tool for on-site monitoring of Hg2+ in water and cosmetic samples.