title: An oligonucleotide-functionalized carbon nanotube chemiresistor for sensitive detection of mercury in saliva.
abstract: Divalent mercuric (Hg(2+)) ion and monomethyl mercury (CH3Hg(+)) are two forms of mercury that are known to be highly toxic to humans. In this work, we present a highly selective, sensitive and label-free chemiresistive biosensor for the detection of both, Hg(2+) and CH3Hg(+) ions using DNA-functionalized single-walled carbon nanotubes (SWNTs). The SWNTs were functionalized with the capture oligonucleotide, polyT, using a linker molecule. The polyT was hybridized with polyA to form a polyT:polyA duplex. Upon exposure to mercury ions, the polyT:polyA duplex dehybridizes and a T-Hg(2+)-T duplex is formed. This structure switch leads to the release of polyA from the SWNT surface and correspondingly a change in the resistance of the chemiresistive biosensor is observed, which is used to quantify the mercury ion concentration. The biosensor showed a wide dynamic range of 0.5 to 100 nM for the detection of CH3Hg(+) ions in buffer solution with a sensitivity of 28.34% per log (nM) of CH3Hg(+). Finally, real world application of the biosensor was demonstrated by the detection of Hg(2+) and CH3Hg(+) ions in simulated saliva samples spiked with a known concentration of mercury ions.
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA. adani@engr.ucr.edu.
authors.forename: Dawit N
authors.initials: DN
authors.lastname: Wordofa
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA. adani@engr.ucr.edu.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Ramnani
authors.affiliation: Department of Bioengineering, University of California, Riverside, California 92521, USA.
authors.forename: Thien-Toan
authors.initials: TT
authors.lastname: Tran
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA. adani@engr.ucr.edu and Material Science and Engineering Program, University of California, Riverside, California 92521, USA.
authors.forename: Ashok
authors.initials: A
authors.lastname: Mulchandani
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D006801:Humans; D008628:Mercury / Q000032:analysis*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009841:Oligonucleotides / Q000737:chemistry*; D012463:Saliva / Q000737:chemistry*
chemical_list: D037742:Nanotubes, Carbon; D009841:Oligonucleotides; D008628:Mercury