Genetic modification of glucose oxidase for improving performance of an amperometric glucose biosensor

Glucose oxidase (GOD) was genetically modified by adding a poly-lysine chain at the C-terminal with a peptide linker inserted between the enzyme and poly-lysine chain. The poly-lysine chain was added in order to anchor more electron transfer mediator, ferrocenecarboxylic acid, to GOD for the purpose of improving sensitivity and stability of glucose biosensors. The modified GOD had similar K(m) and K(cat) to those of the wild type enzyme. After interacted with the electron transfer mediator, the modified enzyme retained 90.01% of its native activity, while the commercial GOD and the wild type GOD (Aspergillus niger) retained only 22.43 and 22.17%, respectively. Screen-printed electrodes coated with the modified GOD, wild type yeast-derived GOD or the commercial GOD were tested in glucose solution of different concentrations. Experimental results showed that the biosensor based on the modified GOD gave the largest signal among the three. In addition, the linear range of the biosensor prepared by the modified GOD could extend to 45 mM, while they were about 20 mM for the biosensors based on the wild type yeast-derived enzyme and the commercial enzyme.