Electrochemical Biosensing

In this chapter, we learn the several electrochemical techniques we may use to develop selective Bio/CMOS interfaces with the aim of detecting human metabolites, therapeutic drugs, or disease biomarkers. Therefore, this chapter opens with the concept of electrochemical biosensing by showing the need for a three-electrode electrochemical cell. The main equations that govern the relationships between the electrical behavior of electrochemical cells and chemical reactions occurring in the cell are derived by the physics of molecular diffusion in liquids. Examples of amperometric biosensing with Bio/CMOS interfaces based on oxidases or cytochromes are furnished as well. Then, the chapter moves on to potentiometric techniques involving two-electrode electrochemical cells and their typical application to ion sensing based on selective membranes. Electrochemical impedance spectroscopy is considered for applications in antibody-based sensing. The equivalent capacitance related to layering effects at the electrochemical interface is deeply discussed, and its measurement is proposed for biosensing based on antibodies or nucleic acids. The most important figures of merits of the Bio/CMOS interfaces obtained for biosensing are then defined: selectivity, sensitivity, and limit of detection.