title: Ternary surface monolayers for ultrasensitive (zeptomole) amperometric detection of nucleic acid hybridization without signal amplification.
abstract: A ternary surface monolayer, consisting of coassembled thiolated capture probe, mercaptohexanol and dithiothreitol, is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers. Remarkably low detection limits down to 40 zmol (in 4 μL samples) as well as only 1 CFU Escherichia coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3',5,5'-tetramethylbenzidine system. Such dramatic improvements in the detection limits (compared to those of common binary alkanethiol interfaces and to those of most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to nonspecific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration "backfillers" that leads to a remarkably low background noise even in the presence of complex sample matrixes. A wide range of surface compositions have been investigated, and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety, and forensic analysis.
authors.affiliation: Department of Nanoengineering, University of California-San Diego, La Jolla, California 92093, Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California 90095, and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Susana
authors.initials: S
authors.lastname: Campuzano
authors.forename: Colin
authors.initials: C
authors.lastname: Halford
authors.forename: David A
authors.initials: DA
authors.lastname: Haake
authors.forename: Joseph
authors.initials: J
authors.lastname: Wang
mesh_terms: D001560:Benzidines / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods*; D004247:DNA / Q000032:analysis*; D004226:Dithioerythritol / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods; D004926:Escherichia coli / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000175:diagnosis; D006801:Humans; D057230:Limit of Detection; D008297:Male; D009693:Nucleic Acid Hybridization / Q000379:methods*; D012329:RNA, Bacterial / Q000032:analysis; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D001560:Benzidines; D012329:RNA, Bacterial; D013438:Sulfhydryl Compounds; C021758:3,3',5,5'-tetramethylbenzidine; D004226:Dithioerythritol; D004247:DNA