Challenges of Electrochemical Impedance Spectroscopy in Protein Biosensing

Abstract

Electrochemical impedance spectroscopy (EIS) measurement, performed in the presence of a redox agent, is a convenient method to measure molecular interactions of electrochemically inactive compounds taking place on the electrode surface. High sensitivity of the method, being highly advantageous, can be also associated with nonspecific impedance changes that could be easily mistaken for specific interactions. Therefore, it is necessary to be aware of all possible causes and perform parallel control experiments to rule them out. We present the results obtained during the early stages of aptamer-based sensor development, utilizing a model system of human alpha thrombin interacting with a thiolated DNA aptamer, immobilized on gold electrodes. EIS measurements took place in the presence of iron ferrocyanides. In addition to known method limitations, that is, inability to discriminate between specific and nonspecific binding (both causing impedance increase), we have found other factors leading to nonspecific impedance changes, such as: (i) initial electrode contamination; (ii) repetitive measurements; (iii) additional cyclic voltammetry (CV) or differential pulse voltammetry (DPV) measurements; and (iv) additional incubations in the buffer between measurements, which have never been discussed before. We suggest ways to overcome the method limitations.

A hydrogel biosensor for high selective and sensitive detection of amyloid-beta oligomers

“…Therefore, EIS has been widely used to detect DNA, protein, or small molecules. 7,37 The Randles equivalent circuit model was used in our system to measure the Nyquist plots ( Figure 1D, inset). Typical EIS spectrum comprises a compressed semicircle in the high frequency region followed by a tail in the lower frequency region.…”

Impedimetric IgG-Biosensor with In-Situ Generation of the Redox-Probe

“…The charge transfer resistance describes the resistance that a redox-probe experiences on an electrode surface with respect to an electron transfer. Generally, biosensors based on EIS use Ferro-/Ferricyanide as redox-probes, but several authors reported that these redox-probes are not suitable for biosensors with gold electrodes because the impedance values increase during multiple measurements [3] and over a longer time range the electrodes are destroyed [4]. Lazar et al [5] have shown that the RCT increases during the first 100 min and then decreases over longer measurement times.…”

G-quadruplex based impedimetric 2-hydroxyfluorene biosensor using hemin as a peroxidase enzyme mimic

“…Especially, electrochemical impedance spectroscopy (EIS) has been proven to be a most powerful and sensitive tool for probing the features of surface-modified electrodes [21]. And EIS biosensors ([Fe(CN) 6 ] 3-/4-as redox probe couple) possess unique advantages, such as the ability to separate the surface binding events from the solution impedance, ease of signal quantification, less damage to the biological interactions being measured, and most importantly, label-free on the DNA strand [22][23][24]. However, to the best of our knowledge, little efforts have been given to the development of biosensors for exploring the 2-HOFlu, and no fluorescent, colorimetric and electrochemical DNA sensors have been reported for 2-HOFlu detection.…”