Third-generation biosensor

Figure 6.7 illustrates the voltammetric response of the third-generation SOD-based 02 biosensors with Cu, Zn-SOD confined onto cystein-modified Au electrode as an example. The presence of 02" in solution essentially increases both the cathodic and anodic peak currents of the SOD compared with its absence [150], Such a redox response was not observed at the bare Au or cysteine-modified Au electrodes in the presence of 02". The observed increase in the anodic and cathodic current response of the Cu, Zn-SOD/cysteine-modified Au electrode in the presence of 02 can be considered to result from the oxidation and reduction of 02, respectively, which are effectively mediated by the SOD confined on the electrode as shown in Scheme 3. Such a bi-directional electromediation (electrocatalysis) by the SOD/cysteine-modified Au electrode is essentially based on the inherent specificity of SOD for the dismutation of 02", i.e. SOD catalyzes both the reduction of 02 to H202 and the oxidation to 02 via a redox cycle of its Cu (II/I) complex moiety as well as the direct electron transfer of SOD realized at the cysteine-modified Au electrode. Thus, this coupling between the electrode and enzyme reactions of SOD could facilitate the development of the third-generation biosensor for 02". ...

To fulfill both the requirement of CFME for the practical applications and the necessity of Au substrate to assemble so-called promoters to construct the third-generation biosensor, Tian el al. have combined the electrochemical deposition of Au nanoparticles (Au-NPs) onto carbon fiber microelectrodes with the self-assembly of a monolayer on these Au-NPs to facilitate the direct electron transfer of SOD at the carbon fiber microelectrode. The strategy enabled a third-generation amperometric 02 biosensor to be readily fabricated on the carbon fiber microelectrode. This CFME-based biosensor is envisaged to have great potential for (he detection of 02" in biological systems [158],... 

Y. Tian, L. Mao, T. Okajima, and T. Ohsaka, Superoxide dismutase-based third-generation biosensor for superoxide anion. Anal. Chem. 74, 2428-2434 (2002). 

M. Viticoli, A. Curulli, A. Cusma, S. Kaciulis, S. Nunziante, L. Pandolfi, F. Valentini, and G. Padeletti, Third-generation biosensors based on Ti02 nanostructured films. Mater. Sci. Engine. C 26, 947-951... 

Third generation biosensors very few cases reported. Active site usually deeply buried within the protein, thus enzyme engineering is required for protein modification to allow electrical wiring between enzyme and electrode. Advantages interferences could be completely eliminated. Disadvantages large amount of coenzyme required, low stability of the enzyme and relatively high applied potential for amperometric detection. Still require the addition of the coenzyme. 

Zhang L, Tian DB, Zhu JJ (2008) Third generation biosensor based on myoglobin-TiOV MWCNTs modified glassy carbon electrode. Chin Chem Lett 19 965-968... 

Gorton L, Lindgren A et al (1999) Direct electron transfer between heme-containing enzymes and electrodes as basis for third generation biosensors. Anal Chim Acta 400 91-108... 

Third generation biosensors—integrating recognition and transduction in electrochemical sensors... 

Fig. 2.1. Illustration of third generation biosensors illustrating the direct electron transfer contact between an enzyme and an electrode and catalytic current generated in the presence of substrate S.

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