Two-dimensional enzyme electrode

D. Gough, J. Lucisano, and P. Tse, Two-dimensional enzyme electrode sensor for glucose. Anal. Chem. 57, 2351-2357 (1985). 

Fig. 44. Schematic layout of a two-dimensional enzyme electrode for glucose. (Redrawn from Gough et al., 1986).

Gough DA, Lucisano JY, Tse HSM (1985) Two-dimensional enzyme electrode scmsor for glucose. Anal Chem 57(12) 2351-2357... 

While direct electron transfer to laccases may help elucidate the mechanism of action of these enzymes it is unlikely that this process will supply sufficient power for a viable implantable biocatalytic fuel cell, because of difficulties associated with the correct orientation of the laccase and the two-dimensional nature of the biocatalytic layer on the surface. However, a recent attempt to immobilize laccase in a carbon dispersion, to provide electrodes with correctly oriented laccase for direct electron transfer, and a higher density of electrode material shows promise [53],... 

Current and power densities achieved with electrodes using the direct electron transfer approach will be limited, however, because of the need to have intimate contact between the two-dimensional electrode surface and a coating monolayer of correctly oriented biocatalyst. The use of small redox molecules that can mediate electron transfer between the biocatalyst and the electrode surface offers an opportunity to improve output from biocatalytic electrodes, as three-dimensional films of biocatalysts may now be used. In addition the distance between the active site of the enzyme and the electrode surface is often too great to allow efficient direct electron transfer. In these cases the electron transfer rate is not effective because of the insulation of the redox active site by the surrounding protein. A redox mediator can shuttle electrons between the enzyme and the surface. In the example of redox mediated biocatalytic oxidation of a fuel, depicted in Fig. 12.3, the enzyme catalyzes the oxidation of the mediator... 

Conventional enzyme electrodes employ disorete-maorosoopio membranes to overcome problems associated with interferences, enzyme immobilization, and electrode fouling. While these types of enzyme electrodes have been commercially developed, there are some limitations with this approach. Some sensors use three relatively thick membranes, resulting in a slow smd complex diffusion path for reactants reaching the enzyme and hydrogen peroxide reaching the electrode. Slow diffusion in this type of system adversely affects the response and recovery time, decreasing sampling rate. Each sensor must be individually constructed, and this construction technique is limited to two-dimensional surfaces. In addition, for sensors that have complex and slow diffusion paths, rates of diffusion must remain constant, otherwise calibration of the biosensor, and more important the maintenance of calibration, are difficult. A variety of factors can influence rates of diffusion, and consequently the performance of the enzyme layer and the performance of the sensor. These complicated, and most often uncharacterizable, properties have made the development of roost biosensors difficult. 

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