Abstract
Most commercially available electrochemical enzyme sensor strips for the measurement of blood glucose use an artificial electron mediator to transfer electrons from the active side of the enzyme to the electrode. One mediator recently gaining attention for commercial sensor strips is hexaammineruthenium(III) chloride. In this study, we investigate and compare the preference of enzyme electrodes with two different FAD-dependent glucose dehydrogenases (FADGDHs) for the mediators hexaammineruthenium(III) chloride, potassium ferricyanide (the most common mediator in commercial sensor strips), and methoxy phenazine methosulfate (mPMS). One FADGDH is a monomeric fungal enzyme, and the other a hetero-trimeric bacterial enzyme. With the latter, which contains a heme-subunit facilitating the electron transfer, similar response currents are obtained with hexaammineruthenium(III), ferricyanide, and mPMS (6.8 µA, 7.5 µA, and 6.4 µA, respectively, for 10 mM glucose). With the fungal FADGDH, similar response currents are obtained with the negatively charged ferricyanide and the uncharged mPMS (5.9 µA and 6.7 µA, respectively, for 10 mM glucose), however, no response current is obtained with hexaammineruthenium(III), which has a strong positive charge. These results show that access of even very small mediators with strong charges to a buried active center can be almost completely blocked by the protein.
Highlights
The market for glucose sensing devices used for glycemic level control is ever expanding due to the increasing number of people suffering from diabetes mellitus worldwide
Native bacterial flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) has a broad substrate specificity and is little suited for glucose has a broad substrate specificity and its is little suited for test strips. bacterial
To confirm substrate specificity of the FADGDHs used in this study, the specific activity of
Summary
The market for glucose sensing devices used for glycemic level control is ever expanding due to the increasing number of people suffering from diabetes mellitus worldwide. Because more and more patients regularly check their blood glucose levels themselves to apply the right treatment, the demand for simple yet accurate devices for the self-monitoring of blood glucose (SMBG) is growing. Current commercially available sensors for SMBG are, for the most part, second-generation electrochemical biosensors. In this type of biosensors, the analyte (glucose) is oxidized by an enzyme (glucose recognition element). The reduced cofactor reduces an artificial electron acceptor (mediator). This mediator is re-oxidized at the electrode, which generates a response current
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