An Oxygen Insensitive Amperometric Glucose Biosensor Based on An Engineered Cellobiose Dehydrogenase: Direct versus Mediated Electron Transfer Responses

Cellobiose dehydrogenase (CDH) is capable of oxidizing cellobiose and related carbohydrates and generating electrical current at carbon-based electrodes through direct electron transfer (DET) or mediated electron transfer (MET) mechanisms. As a result, CDHs have been utilized as biocatalysts in biosensors and biofuel cell anodes. A novel engineered ascomycetous Class II CDH with enhanced glucose activity was tested as a bioelectrocatalyst for application to DET or MET-based glucose biosensors with the electrode component amount selection optimized for maximum current in 5 mM glucose solutions. The optimised DET biosensor showed a similar sensitivity and 3-fold lower K-M,K-app when compared to non-optimised DET sensor based on the same engineered CDH. The optimized MET biosensor had a similar K-M,K-app to non-optimized MET biosensor. However, it showed 15-fold improvement in j(max) and 17-fold improvement in sensitivity over the DET biosensor. The sensor signals are not affected by the presence of oxygen, although operation in artificial serum results in 43 % and 28 % lower sensitivity for the DET and MET sensors, respectively. While no individually tested potential interferent breaches a mean absolute relative difference of 20 % of the current, the cumulative co-operative effect in complex media, such as artificial serum, decreases the glucose oxidation current signal.