title: Covalent linking DNA to graphene oxide and its comparison with physisorbed probes for Hg²⁺ detection.
abstract: Graphene oxide (GO) has attracted extensive research interest as a platform for DNA adsorption and biosensor development. While most researchers use simple physisorption of fluorescently labeled DNA, covalent sensors are less susceptible to non-specific probe displacement and minimize false positive results. In this work, three thymine-rich DNA probes of different lengths are modified on their 3'-end with an amino group for covalent conjugation to GO. They also each contain an internally labeled fluorophore so that Hg(2+) binding can lead to a large distance increase between the fluorophore and the GO surface for fluorescence signaling. Hg(2+)-dependent fluorescence signaling from the covalent sensors are compared with that from the non-covalent sensors in terms of sensitivity, selectivity, signaling kinetics, and continuous monitoring. The covalent sensors are much more stable and resistant to non-specific probe displacement, while still retaining high sensitivity and similar selectivity. The detection limits are 16.3 and 20.6 nM Hg(2+), respectively, for the covalent and non-covalent sensors, and detection of spiked Hg(2+) in Lake Ontario water is demonstrated.
authors.affiliation: College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China; Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Chang
authors.initials: C
authors.lastname: Lu
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Po-Jung
authors.initials: PJ
authors.lastname: Jimmy Huang
authors.affiliation: College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China. Electronic address: ybying@zju.edu.cn.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Ying
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1. Electronic address: liujw@uwaterloo.ca.
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D015374:Biosensing Techniques; D004247:DNA / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry; D008628:Mercury / Q000302:isolation & purification* / Q000633:toxicity; D010087:Oxides / Q000737:chemistry; D013941:Thymine / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D010087:Oxides; D006108:Graphite; D004247:DNA; D008628:Mercury; D013941:Thymine
keywords: Biosensors; Covalent; DNA; Fluorescence; Graphene; Mercury