Electrochemical Enzyme Biosensors

Dipartimento di Chimica Ugo Schiff, Universitd degli Studi di Firenze, Vm della Lastruccia 3, 50019, Sesto Fiorentino, Italy 

Enzymes (and all biological elements, such as tissues, cells, microorganisms, which contain enzymes) represent the class of what are called catalytic elements. Enzyme biosensors have several advantages. These include the catalytic amplification of the biosensor response by modulation of the enzyme activity with respect to the target analyte a stable source of 

Edited by Alberto Escarpa, Marfa Cristina Gonzalez and Miguel Angel Lopez. 2015 John Wiley Sons, Ltd. Published 2015 by John Wiley Sons, Ltd. 

Among the enzymes that are commercially available, the most often used in biosensors are oxidoreductase and hydrolase, like glucose oxidase, horseradish peroxidase, and alkaline phosphatase. In particular, glucose oxidase continues to be the most stable and specific enzyme thaf can be easily obfained in large quantities. 

In principle, enzyme-based biosensors have potential application in the agro-food analysis, within three main areas that are food safety, food quality, and process control. The term food safety involves the concept of the production and marketing of harmless food, monitoring the presence of contaminants, such as residues of pesticides, fertilizers, heavy metals, and other toxic organic compounds also used as additives. Food quality is related not only to safety but mainly to nutritional value and acceptability. Thus, in this context freshness, appearance, flavor, texture, and composition are food characteristics that have to be controlled. Moreover, enzyme biosensors allow the determination and quantification, on-line, of compounds of interest in process control, such as fermentation, sugar, alcohols contents, and so on. 

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Application of electrochemical enzyme biosensors for food quality control... 

Some recent developments in materials for use in electrochemical enzyme biosensors will illustrate the strategy of sensor build-up and sensor characterisation by electrochemical and non-electrochemical techniques, illustrated by the type of information that has been obtained at the molecular and nanometre levels. Any construction strategy that is developed has to consider easy access to the enzyme active site by the enzyme substrate and easy removal of products with a convenient transduction mechanism for production of an electrical signal. Characterisation of different approaches will be presented. 

Fig. 6.4 Schematic construction of redox-mediated electrochemical enzyme biosensor...

Considerable effort has been dedicated to die investigation of different surface modification processes of metal and carbon electrodes in the construction of electrochemical enzyme biosensors with separate redox mediator and enzyme layers, see Fig. 6.4. 

Two examples of this layer-by-layer strategy are illustrated. In the first, electrochemical enzyme biosensors for glucose were prepared. Indium tin oxide (ITO) glass electrodes were modified by self-assembly using an immersion technique with up to three bUayers of polyamidoamine (PAMAM) dendrimers containing gold nanoparticles of diameter 3 nm and poly(vinyl sulfonate) (PVS). The gold... 

Serra, B., A. J. Reviejo, and J. M. Pingarron. 2007. Application of electrochemical enzyme biosensors for food quality control. Compr. Anal. Chem. 49 255-298. 

Sanchez S, Pumera M, Cabruja E, Fabregas E (2007) Carbon nano-tube/polysulfone composite screen-printed electrochemical enzyme biosensor. Analyst 132 (2) 142-147... 

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