Second generation of Glucose Biosensors : Biofuel cells and Neurotransitters

Different FAD dependent GDH enzymes together with the Os-redox polymer Os(4,4′-dimethyl-2,2′-bipyridine)2(PVI)10Cl]+ and a modified graphite electrode was shown to have distinct selectivity and high turnover rates towards glucose. The results of this study suggest that such electrodes may be applied either for glucose determination or as bioanodes in glucose biofuel cells. Further, higher current density was obtained when the deglycosylated form of FAD-GcGDH was used under the same conditions. This clearly confirms the effect of enzyme downsizing to enhance communication between the enzyme and the electrode surface. Using a series of FAD dependent enzymes such as: GOx, PDH, CDH, and GDH with the composite PVP-Os-(bpy)2-Cl connected to chitosan via a linker. The results show that this disclosed new strategy would be suitable for either constructingor developing 2nd- generation biosensors. The use of Man-Os(VI)tmen as a new version of the Os-redox polymer to build up (non-enzymatic) Neurotransmitter sensors, by the simple adsorption route to a modified graphite electrode, for detection of DA in the presence of other analyte compounds e. g. AA and UA successfully proved, resulting in a multi-analyte sensor. In another study of the same polymer Man-Os(VI)tmen, this was applied for selective detection of DA, by an alternative method where the modified graphite electrode based Man-Os(VI)tmen polymer was combined with either multiwall carbon nanotubes decorated with gold nano-particles Au-NPs-MWCNT or by a poly(sodium-4 styrene sulfonate) (PSS). The electrode modified by the use of Au-NPs-MWCNT shows a substantial improvement of the signal for DA detection compared to that of PSS. The Man-Os(VI)tmen redox polymer was also used as a mediator to modified graphite electrode with a AspGDH based enzyme together with glucose as cosubstrate. This improved the output current for the analyte DA, by taking advantage of the Man-Os(VI)tmen redox polymer affinity towards DA oxidation that we previously reported. Hence, the suggested biosensor was successfully shown a significant improve in the output current for DA sensing