Electrochemical biosensors gold electrode

Key words Electrochemical biosensors, Gold nanoparticles, Enzyme biosensors, Immunosensors, Composite electrodes, Carbon nanotubes. 

S. Campuzano, R. Galvez, M. Pedrero, F.J. Manuel de Villena and J.M. Pingarron, An integrated electrochemical fructose biosensor based on tetrathiafulvalene-modified self-assembled monolayers on gold electrodes, Anal. Bioanal. Chem., 377(4) (2003) 600-607. 

Determination of gluconic acid in honey samples using an integrated electrochemical biosensor based on self-assembled monolayer modified gold electrodes... 

The diphenylalanine nanotube sensors were based on the observation that peptide nanotubes improve the electrochemical properties of graphite and gold electrodes when deposited directly onto the electrode surface (Yemini et al., 2005b). The high surface area of the nanotubes and the potential alignment of aromatic residues are thought to contribute to the observed increase in conductivity. This property makes nanotube-coated electrodes and hydrophobin-coated electrodes suitable for use as amperometric biosensors that produce a current in response to an electrical potential across two electrodes. 

Nowadays, the construction of electrochemical biosensors based on the use of gold nanoparticles constitutes an intensive research area because of the unique advantages that this nanomaterial lends to biosensing devices. So, gold nanoparticles provide a stable surface for immobilization of biomolecules with no loss of their biological activity. Moreover, they facilitate direct electron transfer between redox proteins and electrode materials, and constitute useful interfaces for the electrocatalysis of redox processes of molecules such as H202 or NADH involved in many biochemical reactions (1, 2). 

Manso, J., Mena, M.L., Yanez-Sedeno, P., Pingarron, J.M. (2007) Electrochemical biosensors based on colloidal gold-carbon nanotubes-Teflon composite electrodes. J. Electroanal. Chem., 603, 1-7... 

NAD was covalently linked via a PQQ spacer to a gold electrode. This modified electrode is capable of binding LDH over the exposed nicotinamide groups. Upon oxidation of lactate to pyruvate the excess electrons tunnel from NADH in the active site to PQQ and eventually to the anode. Thus, a kind of electrical linkage between the enzyme and the electrode is established. The enzymes were crosslinked, as LDH is a homotetramer and might dissociate during the reaction. This approach is not only useful for electrochemical biosensors but might be transferred to other oxidoreductase reactions. 

The characteristic electrochemical behavior of enzyme, protein and Upid monolayers adhered to SAMs derived from thiols on gold surfaces may be applied to the development of biosensors. The gold electrodes resulting from incorporation of monensin (203) and vaUnomycin (204) into bilayers, consisting of the SAMs of aUsanethiol covered by a Upid monolayer, have high sensitivity for monovalent ions . A gold electrode with a SAM of a modified /3-cyclodextrin was proposed for electrochemical detection of organic compounds . 

A very recent example of the use of this redox probe in an aptamer-based biosensor was published by Kim et al. [33]. An electrochemical biosensor for ox3d etracycline detection was developed using ssDNA aptamer immobilized on gold interdigitated array (IDA) electrode chip (Fig. 2.7). Cyclic voltammetry and square wave voltammetry were used to measure the current at the electrode chip... 

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