Recent Progress in Electrochemical Immunosensors

Abstract

Biosensors used for medical diagnosis work by analyzing physiological fluids. Antibodies have been frequently used as molecular recognition molecules for the specific binding of target analytes from complex biological solutions. Electrochemistry has been introduced for the measurement of quantitative signals from transducer-bound analytes for many reasons, including good sensitivity. Recently, numerous electrochemical immunosensors have been developed and various strategies have been proposed to detect biomarkers. In this paper, the recent progress in electrochemical immunosensors is reviewed. In particular, we focused on the immobilization methods using antibodies for voltammetric, amperometric, impedimetric, and electrochemiluminescent immunosensors.

Keywords: amperometric immunosensors; biosensors; electrochemical immunosensors; eletrochemiluminescent immunosensors; immunosensors; impedimetric immunosensors; voltammetric immunosensors.

Figure 1

Examples of voltammetric immunosensors with non-covalently immobilized antibodies. (A) Schematic diagram of CRP immunosensor. Antibodies were immobilized on the polymer-modified electrode by the charge interaction. Reproduced with permission from [30]. Copyright (2020) John Wiley and Sons., Inc. (B) Immunosensor with non-covalently immobilized antibodies on AuNPs. Reproduced with permission from [33]. Copyright (2018) Elsevier. (C) Schematic diagram of immunosensor using gold and carbon-based materials at the same time. Reproduced with permission from [41]. Copyright (2021) Elsevier.

Figure 3

Examples of amperometric immunosensors with non-covalently immobilized antibodies. (a) Sandwich amperometric immunosensor. The immunoaffinity layer was fabricated by the direct treatment of antibodies on the electrode. Reproduced with permission [53]. Copyright (2018) Elsevier. (b) Composites-based immunosensor. Antibodies were immobilized on the PdAg nanosphere-modified electrode by physical adsorption. Reproduced with permission [55]. Copyright (2020) Elsevier. (c) AuNP-based immunosensor. An immunoaffinity layer was formed by immobilizing antibodies on the AuNP-coated electrode. Reproduced with permission [57]. Copyright (2020) Elsevier.

Figure 3

Examples of amperometric immunosensors with non-covalently immobilized antibodies. (a) Sandwich amperometric immunosensor. The immunoaffinity layer was fabricated by the direct treatment of antibodies on the electrode. Reproduced with permission [53]. Copyright (2018) Elsevier. (b) Composites-based immunosensor. Antibodies were immobilized on the PdAg nanosphere-modified electrode by physical adsorption. Reproduced with permission [55]. Copyright (2020) Elsevier. (c) AuNP-based immunosensor. An immunoaffinity layer was formed by immobilizing antibodies on the AuNP-coated electrode. Reproduced with permission [57]. Copyright (2020) Elsevier.

Figure 4

Examples of amperometric immunosensors with covalently immobilized antibodies. (a) Magnetite nanoparticles and MWCNT-based immunosensor. Antibodies were chemically immobilized with carboxylated MWCNTs through EDC/NHS chemistry. Reproduced with permission [61]. Copyright (2020) Elsevier. (b) AuNP-based immunosensor. Antibodies were immobilized on the amine group of the PAuNP-AMAM dendrimer nanocomposite using glutaraldehyde cross-linking. Reproduced with permission [63]. Copyright (2020) Elsevier.

Figure 2

Examples of voltammetric immunosensors with covalently immobilized antibodies. (a) Immunosensor based on carboxyl functionalized GO. Antibodies were chemically immobilized using EDC chemistry. Reproduced with permission from [44]. Copyright (2018) Elsevier. (b) CA19-9 biosensor based on CS-MWCNT-Fe₃O₄. Antibodies were immobilized using glutaraldehyde. Reproduced with permission from [46]. Copyright (2021) Elsevier.

Figure 5

Examples of impedimetric immunosensors with non-covalently immobilized antibodies. (a) AuNR-based immunosensor. Antibodies were immobilized on the AuNR-modified electrode by physical adsorption. Reproduced with permission [73]. Copyright (2020) Elsevier. (b) MWCNT–AuNP nanocomposite-based immunosensor. The capture antibodies were immobilized on MWCNT–AuNP nanocomposite using physical adsorption. Reproduced with permission [74]. Copyright (2021) Elsevier.

Figure 6

Example of impedimetric immunosensors with covalently immobilized antibodies. MWCNT–AuNP-based immunosensor was fabricated by the immobilization of antibodies on carboxyl-functionalized MWCNT–AuNP using EDC/NHS chemistry. Reproduced with permission [83]. Copyright (2018) Elsevier.

Figure 7

Examples of ECL immunosensors with physically adsorbed capture antibodies. Antibodies were immobilized on AgNPs to form an immunoaffinity layer. Reproduced with permission [100]. Copyright (2020) American Chemical Society.

Figure 8

Examples of ECL immunosensors with covalently immobilized capture antibodies. The capture antibodies were chemically immobilized on a PICA–AuNP nanocomposite-modified electrode using EDC/NHS. Reproduced with permission [110]. Copyright (2020) Elsevier.