title: Direct electrical transduction of antibody binding to a covalent virus layer using electrochemical impedance.
abstract: Electrochemical impedance spectroscopy is used to detect the binding of a 148.2 kDa antibody to a "covalent virus layer" (CVL) immobilized on a gold electrode. The CVL consisted of M13 phage particles covalently anchored to a 3 mm diameter gold disk electrode. The ability of the CVL to distinguish this antibody ("p-Ab") from a second, nonbinding antibody ("n-Ab") was evaluated as a function of the frequency and phase of the measured current relative to the applied voltage. The binding of p-Ab to the CVL was correlated with a change in the resistance, reducing it at low frequency (1-40 Hz) while increasing it at high frequency (2-140 kHz). The capacitance of the CVL was virtually uncorrelated with p-Ab binding. At both low and high frequency, the electrode resistance was linearly dependent on the p-Ab concentration from 20 to 266 nM but noise compromised the reproducibility of the p-Ab measurement at frequencies below 40 Hz. A "signal-to-noise" ratio for antibody detection was computed based upon the ratio between the measured resistance change upon p-Ab binding and the standard deviation of this change obtained from multiple measurements. In spite of the fact that the impedance change upon p-Ab binding in the low frequency domain was more than 100 times larger than that measured at high frequency, the S/N ratio at high frequency was higher and virtually independent of frequency from 4 to 140 kHz. Attempts to release p-Ab from the CVL using 0.05 M HCl, as previously described for mass-based detection, caused a loss of sensitivity that may be associated with a transition of these phage particles within the CVL from a linear to a coiled conformation at low pH.
authors.affiliation: Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
authors.forename: Li-Mei C
authors.initials: LM
authors.lastname: Yang
authors.forename: Juan E
authors.initials: JE
authors.lastname: Diaz
authors.forename: Theresa M
authors.initials: TM
authors.lastname: McIntire
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Weiss
authors.forename: Reginald M
authors.initials: RM
authors.lastname: Penner
mesh_terms: D000914:Antibodies, Viral / Q000302:isolation & purification*; D000937:Antigen-Antibody Reactions; D001435:Bacteriophages / Q000276:immunology; D015374:Biosensing Techniques / Q000379:methods* / Q000592:standards; D017097:Electric Impedance; D004566:Electrodes / Q000382:microbiology; D014780:Viruses / Q000276:immunology
chemical_list: D000914:Antibodies, Viral