title: Hg(2+) 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 the 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, containing one, three and five PS-RNA linkages, respectively, were tested. 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 released from NGO due to the cleavage reaction, resulting in a 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+) more slowly and was inhibited by high NaCl concentrations, while the PS-RNA probe was more tolerant to different buffer conditions. This work indicates a new method for interfacing DNA with NGO for Hg(2+) detection.
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada. liujw@uwaterloo.ca.
authors.forename: Po-Jung Jimmy
authors.initials: PJ
authors.lastname: Huang
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada. liujw@uwaterloo.ca.
authors.forename: Courtney
authors.initials: C
authors.lastname: van Ballegooie
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada. liujw@uwaterloo.ca.
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D015374:Biosensing Techniques; D004247:DNA / Q000737:chemistry; D006108:Graphite; D008628:Mercury / Q000032:analysis*; D010087:Oxides; D015347:RNA Probes; D013941:Thymine
chemical_list: D010087:Oxides; D015347:RNA Probes; D006108:Graphite; D004247:DNA; D008628:Mercury; D013941:Thymine