Hg²⁺ detection using a phosphorothioate RNA probe adsorbed on graphene oxide and a comparison with thymine-rich DNA

Abstract

Mercury is a highly toxic heavy metal and many DNA-based biosensors have been recently developed for Hg 2+ detection in water. Among them, thymine-rich DNA is the most commonly used for designing Hg 2+ sensors. However, the thymine-Hg 2+ interaction is strongly affected by buffer conditions. We recently reported a molecular beacon containing phosphorothioate (PS)-modified RNA linkages that can be cleaved by Hg 2+ . In this work, the fluorescence quenching and DNA adsorption properties of nano-sized graphene oxide (NGO) were used to develop a new sensor using the PS-RNA chemistry. Three DNA probes were tested, containing one, three and five PS-RNA linkages, respectively. Finally, a fluorophore-labeled poly-A DNA with five PS-RNA linkages was selected and adsorbed by NGO. In the presence of Hg 2+ , the fluorophore was release from NGO due to the cleavage reaction, resulting in fluorescence enhancement. This sensor is highly selective for Hg 2+ with a detection limit of 8.5 nM Hg 2+ . For comparison, a fluorophore-labeled poly-T DNA was also tested, which responded to Hg 2+ slower and was inhibited by high NaCl concentrations, while the PS-RNA probe was more tolerable to different buffer conditions. This work indicates a new way of interfacing DNA with NGO for Hg 2+ detection.3

Reusable pectin‐coated magnetic nanosorbent functionalized with an aptamer for highly selective Hg2+ detection

“…Ono and coworkers have first reported that Hg 2+ can specifically interact with thymine–thymine (T–T) mismatch sites of a DNA duplex, resulting in stable formation of T–Hg 2+ –T complexes with a hairpin structure 39,51,52 . Since then, many works have been developed for the detection of Hg 2+ based on the T–Hg 2+ –T interaction using various types of materials 2 such as carbon nanotubes, 53 quantum dots, 54 graphene, 55,56 silica nanoparticles, 57 gold nanoparticles, 58 silver nanoclusters, 59 and magnetite nanoparticles 60 …”

Acenaphtoquinoxaline as a selective fluorescent sensor for Hg (II) detection: experimental and theoretical studies

“…However, some prepared sensors have much more detection limit to Hg 2+ ion detection in high sensitivity, most of these receptors are difficult to prepare, or the reactions are not cost-effective. Herein, we prepared a fluorescent sensor by organic synthesis, which has some superior as simple operation, low-cost starting material, avoiding by-product, high yield, and in short reaction time [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ].…”

l‐Cysteine modified silver nanoparticles‐based colorimetric sensing for the sensitive determination of Hg2+ in aqueous solutions

“…However, this Hg 2+ ‐driven T–T mismatch could be easily affected by certain reaction buffer conditions such as temperature, pH, ionic strength, and ion species. [ 21–24 ] Apart from these strategies, DNAzymes have been also generally used based on their specific binding to Hg 2+ . [ 25 ] However, the issue of low catalytic efficiency has limited their downstream applications.…”