Current Technologies of Electrochemical Immunosensors: Perspective on Signal Amplification

Abstract

An electrochemical immunosensor employs antibodies as capture and detection means to produce electrical charges for the quantitative analysis of target molecules. This sensor type can be utilized as a miniaturized device for the detection of point-of-care testing (POCT). Achieving high-performance analysis regarding sensitivity has been one of the key issues with developing this type of biosensor system. Many modern nanotechnology efforts allowed for the development of innovative electrochemical biosensors with high sensitivity by employing various nanomaterials that facilitate the electron transfer and carrying capacity of signal tracers in combination with surface modification and bioconjugation techniques. In this review, we introduce novel nanomaterials (e.g., carbon nanotube, graphene, indium tin oxide, nanowire and metallic nanoparticles) in order to construct a high-performance electrode. Also, we describe how to increase the number of signal tracers by employing nanomaterials as carriers and making the polymeric enzyme complex associated with redox cycling for signal amplification. The pros and cons of each method are considered throughout this review. We expect that these reviewed strategies for signal enhancement will be applied to the next versions of lateral-flow paper chromatography and microfluidic immunosensor, which are considered the most practical POCT biosensor platforms.

Keywords: electrochemical immunosensor; electrode scaffold; labeling techniques; nanomaterials; point-of-care testing; signal amplification.

Figure 1

Basic analytical principle of electrochemical immunosensor.

Figure 2

Nanomaterials used as electrodes or supporting solid matrices to enhance the analytical performance of electrochemical immunosensing.

Figure 3

Schematic representation of labeling approaches for the signal amplification of electrochemical immunosensor. The labeling techniques can be categorized as (a) nanocarrier, (b) electroactive nanotracer, (c) enzyme-based nanopolymer and (d) redox cycling of enzyme reactions, which enable an electrochemical signal enhancement.