title: Simultaneous measurement of nonlinearity and electrochemical impedance for protein sensing using two-tone excitation.
abstract: Impedance biosensors detect the binding of a target to an immobilized probe by quantifying changes in the impedance of the electrode-electrolyte interface. The interface's I-V relationship is inherently nonlinear, varying with DC bias, and target binding can alter the degree of nonlinearity. We propose and demonstrate a method to simultaneously measure the nonlinearity and conventional small-signal impedance using intermodulation products from a two-tone input. Intermodulation amplitudes accurately reflect the impedance's manually-measured voltage dependence. We demonstrate that changes in nonlinearity can discriminate protein binding. Our measurements suggest that target binding can alter nonlinearity via the voltage dependence of the ionic double layer.
authors.affiliation: Stanford Genome Technology Center, Stanford University Dept. of Biochemistry, USA.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Daniels
authors.forename: Erik P
authors.initials: EP
authors.lastname: Anderson
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Lee
authors.forename: Nader
authors.initials: N
authors.lastname: Pourmand
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D017076:Computer-Aided Design; D017097:Electric Impedance; D004563:Electrochemistry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008839:Microelectrodes; D017711:Nonlinear Dynamics; D025941:Protein Interaction Mapping / Q000295:instrumentation*; D011506:Proteins / Q000032:analysis* / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*
chemical_list: D011506:Proteins