Electrochemical biosensors and nanobiosensors

Abstract

Electrochemical techniques have great promise for low-cost miniaturised easy-to-use portable devices for a wide range of applications-in particular, medical diagnosis and environmental monitoring. Different techniques can be used for biosensing, with amperometric devices taking the central role due to their widespread application in glucose monitoring. In fact, glucose biosensing takes an approximately 70% share of the biosensor market due to the need for diabetic patients to monitor their sugar levels several times a day, making it an appealing commercial market.In this review, we present the basic principles of electrochemical biosensor devices. A description of the different generations of glucose sensors is used to describe in some detail the operation of amperometric sensors and how the introduction of mediators can enhance the performance of the sensors. Electrochemical impedance spectroscopy is a technique being increasingly used in devices due to its ability to detect variations in resistance and capacitance upon binding events. Novel advances in electrochemical sensors, due to the use of nanomaterials such as carbon nanotubes and graphene, are presented as well as future directions that the field is taking.

Keywords: amperometric biosensor; biosensor; carbon nanotubes; chronocoulometry; electrochemical impedance spectroscopy; electrochemistry; glucose; graphene; reduced graphene oxide.

Figure 1.. Diagrams of oxygen-linked (a) and hydrogen peroxide-linked (b) first-generation amperometric biosensors for glucose detection

Figure 2.. Diagrammatic representation of the architecture of a second-generation amperometric biosensor

Figure 3.. Diagrammatic representation of the architecture of a third-generation amperometric biosensor

Figure 4.. EIS Nyquist plot (Z_imag against Z_real) and Randles circuit (W is a so-called Warburg element, which accounts for diffusion processes)

Figure 5.. A scheme showing how graphene could be ideally rolled-up to form single- or multi-walled carbon nanotubes (courtesy: K. Banerjee, California University)

Figure 6.. Cyclic voltammograms acquired on screen-printed rhodium–graphite electrodes modified with a metalloprotein: standard electrode (1), modified with gold nanoparticles (2), modified with MWCNTs (3) (reprinted from [35] with permission from Elsevier)

Figure 7.. A scheme showing the various ways graphene and graphene-based material can be prepared

CRGO, chemically reduced graphene oxide; TRGO, thermally reduced graphene oxide; ERGO, electrochemically reduced graphene oxide (reprinted from [42] with permission from Elsevier)