Regenerable DNA-Functionalized Hydrogels for Ultrasensitive, Instrument-Free Mercury(II) Detection and Removal in Water

Abstract

Mercury is a highly toxic environmental pollutant with bioaccumulative properties. Therefore, new materials are required to not only detect but also effectively remove mercury from environmental sources such as water. We herein describe a polyacrylamide hydrogel-based sensor functionalized with a thymine-rich DNA that can simultaneously detect and remove mercury from water. Detection is achieved by selective binding of Hg2+ between two thymine bases, inducing a hairpin structure where, upon addition of SYBR Green I dye, green fluorescence is observed. In the absence of Hg2+, however, addition of the dye results in yellow fluorescence. Using the naked eye, the detection limit in a 50 mL water sample is 10 nM Hg2+. This sensor can be regenerated using a simple acid treatment and can remove Hg2+ from water at a rate of ∼1 h−1. This sensor was also used to detect and remove Hg2+ from samples of Lake Ontario water spiked with mercury. In addition, these hydrogel-based sensors are resistant to nuclease and can be rehydrated from dried gels for storage and DNA protection. Similar methods can be used to functionalize hydrogels with other nucleic acids, proteins, and small molecules for environmental and biomedical applications.