Characterization of different FAD-dependent glucose dehydrogenases for possible use in glucose-based biosensors and biofuel cells

In this study, different flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) were characterized electrochemically after “wiring” them with an osmium redox polymer [Os(4,4′-dimethyl-2,2′-bipyridine)2(PVI)10Cl]+ on graphite electrodes. One tested FADGDH was that recently discovered in Glomerella cingulata (GcGDH), another was the recombinant form expressed in Pichia pastoris (rGcGDH), and the third was a commercially available glycosylated enzyme from Aspergillus sp. (AspGDH). The performance of the Os-polymer “wired” GDHs on graphite electrodes was tested with glucose as the substrate. Optimal operational conditions and analytical characteristics like sensitivity, linear ranges and current density of the different FADGDHs were determined. The performance of all three types of FADGDHs was studied at physiological conditions (pH 7.4). The current densities measured at a 20 mM glucose concentration were 494 ± 17, 370 ± 24, and 389 ± 19 μA cm−2 for GcGDH, rGcGDH, and AspGDH, respectively. The sensitivities towards glucose were 2.16, 1.90, and 1.42 μA mM−1 for GcGDH, rGcGDH, and AspGDH, respectively. Additionally, deglycosylated rGcGDH (dgrGcGDH) was investigated to see whether the reduced glycosylation would have an effect, e.g., a higher current density, which was indeed found. GcGDH/Os-polymer modified electrodes were also used and investigated for their selectivity for a number of different sugars

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

Subnanomolar determination of dopamine by electrochemical sensor based on AuNPs- MWCNTs and mannan-Os (VI) adducts

Electroactive adducts, comprising 3α,6α–mannan attached to the six-valent osmium complex with N,N,N´,N?-tetramethylenediamine (simply denoted, Man- Os (VI) tmen) was immobilized on the surface of graphite electrodes via a simple adsorption route and then covered with poly(sodium-4 styrene sulfonate) (PSS). Cyclic voltammograms of modified electrodes GE/Man-Os (VI) tmen showed a clear and well-resolved anodic peak for 1 mM of dopamine DA, ascorbate AA, and urate UA at the potential range of -50 to +350 mV vs. Ag|AgCl|(KClsat.) the sensor GE/Man-Os (VI) tmen/PSS was successfully used for sensitive and selective determination of DA in the presence of an excess concentration of AA and UA, 5 mM and 0.5 mM respectively, using differential pulse voltammetry. Under optimized conditions, the peak current densities were linear from 0.1 nM to 20 μM of DA with a sensitivity of 358 μA μΜ-1 and a detection limit LOD (3SD/slope) of 2.8 nM. Further modifying of the sensor using multiwall carbon nanotubes decorated with gold nanoparticles (AuNPs-MWCNTs) led to substantial improvement in its analytical characteristics. The linear response of the electrode modified GE/ AuNPs-MWCNT/Man-Os (VI) tmen to DA was spanned from 1 pM to 40 μM with a high sensitivity of 624.49 μA μΜ-1 and a LOD (3SD/slope) of 0.17 pM

Characterization of different fad-dependent glucose dehydrogenases for possible use in glucose-based biosensors and biofuel cells

In this study, different flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) were characterized electrochemically after "wiring" them with an osmium redox polymer [Os(4,4\u27-dimethyl-2,2\u27-bipyridine)(2)(PVI)(10)Cl](+) on graphite electrodes. One tested FADGDH was that recently discovered in Glomerella cingulata (GcGDH), another was the recombinant form expressed in Pichia pastoris (rGcGDH), and the third was a commercially available glycosylated enzyme from Aspergillus sp. (AspGDH). The performance of the Os-polymer "wired" GDHs on graphite electrodes was tested with glucose as the substrate. Optimal operational conditions and analytical characteristics like sensitivity, linear ranges and current density of the different FADGDHs were determined. The performance of all three types of FADGDHs was studied at physiological conditions (pH 7.4). The current densities measured at a 20 mM glucose concentration were 494 +/- 17, 370 +/- 24, and 389 +/- 19 mu A cm(-2) for GcGDH, rGcGDH, and AspGDH, respectively. The sensitivities towards glucose were 2.16, 1.90, and 1.42 mu A mM(-1) for GcGDH, rGcGDH, and AspGDH, respectively. Additionally, deglycosylated rGcGDH (dgrGcGDH) was investigated to see whether the reduced glycosylation would have an effect, e.g., a higher current density, which was indeed found. GcGDH/Os-polymer modified electrodes were also used and investigated for their selectivity for a number of different sugars

Characterization of different fad-dependent glucose dehydrogenases for possible use in glucose-based biosensors and biofuel cells

In this study, different flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) were characterized electrochemically after "wiring" them with an osmium redox polymer [Os(4,4\u27-dimethyl-2,2\u27-bipyridine)(2)(PVI)(10)Cl](+) on graphite electrodes. One tested FADGDH was that recently discovered in Glomerella cingulata (GcGDH), another was the recombinant form expressed in Pichia pastoris (rGcGDH), and the third was a commercially available glycosylated enzyme from Aspergillus sp. (AspGDH). The performance of the Os-polymer "wired" GDHs on graphite electrodes was tested with glucose as the substrate. Optimal operational conditions and analytical characteristics like sensitivity, linear ranges and current density of the different FADGDHs were determined. The performance of all three types of FADGDHs was studied at physiological conditions (pH 7.4). The current densities measured at a 20 mM glucose concentration were 494 +/- 17, 370 +/- 24, and 389 +/- 19 mu A cm(-2) for GcGDH, rGcGDH, and AspGDH, respectively. The sensitivities towards glucose were 2.16, 1.90, and 1.42 mu A mM(-1) for GcGDH, rGcGDH, and AspGDH, respectively. Additionally, deglycosylated rGcGDH (dgrGcGDH) was investigated to see whether the reduced glycosylation would have an effect, e.g., a higher current density, which was indeed found. GcGDH/Os-polymer modified electrodes were also used and investigated for their selectivity for a number of different sugars