Electrochemical Detection of Proteins

Abstract

The advantages of electrochemical methods, such as low cost, rapidity, and sensitivity, make these methods very promising in the booming fields of proteomics and biomedicine. Electroanalysis of proteins relies on redox properties of nonprotein centers within conjugated proteins, application of various labels attached to the protein molecule, or label‐free detection of nonconjugated proteins based on their intrinsic electroactivity. Until recently, electrochemistry of proteins was mainly focused on a relatively small group of conjugated proteins, yielding reversible electrochemistry. This article discusses the new methods that were developed to detect and analyze practically all proteins. Different strategies for electrochemical detection of proteins are presented. Electrode modification by biomolecular receptors (antibodies, aptamers) and their potential use for detection of specific proteins, e.g. disease markers, can be utilized in the development of various sensors. Label‐free electrochemical study of nonconjugated proteins, involving impedance measurements at various electrodes, faradaic signals of tyrosine and tryptophan residues at carbon electrodes and cysteine residues, and electrocatalytic signals at mercury and solid amalgam electrodes have been used. Among them, well‐developed chronopotentiometric peak (peak H) due to catalytic hydrogen evolution shows remarkable sensitivity to local and global changes in protein structure. Recent developments in protein electrochemistry open the way for application of electrochemical analysis in proteomics and biomedicine.

Electrochemistry of Nonconjugated Proteins and Glycoproteins. Toward Sensors for Biomedicine and Glycomics

“…), some contain one or more nonprotein redox centers, essential for direct electron transfer (DET) between the protein and its natural acceptor or donor (e.g., metalloproteins). Under conditions when the redox center is sufficiently close to the electrode, DET between this center and the electrode may take place (reviewed in refs − ). The first papers on DET were published by the end of the 1970s. − Pioneering studies described interaction of cytochrome c with either tin-doped indium oxide, 4,4′-bipyridine-modified gold electrode, or mercury electrode .…”

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

“…Protein physisorption is very often carried out through hydrophobic and electrostatic interactions (Figure 6). In general, it has been demonstrated that a strong physisorption of proteins occurs on bare surfaces of CPE and SPCE, as mentioned earlier [84,85].…”

“…It has been shown that a strong adsorption of proteins occurs on highly oriented pyrolytic graphite, carbon paste electrode (CPE) or screen printed carbon electrode (SPCE) surfaces. Despite the rearrangement or structural unfolding of the protein, a partial or complete denaturation of the protein does not occur, as it preserves its binding capacity, probably due to an increase in bio-compatibility of the electrode surface [84,85]. In contrast, in bare metal electrodes such as mercury, silver, gold and platinum the unfolding of the protein leads to its denaturation [86,87].…”

“…In the case of alkanethiol, the alkane aliphatic chain acts as a spacer arm in order to increase the degrees of freedom of the SAM and, in general, of the supramolecular architecture. Thiol tends to form a metal-S bond with the electrode surface leaving the head group exposed [85,146].…”