Improving the performance of glutamate microsensors by purification of ascorbate oxidase

Enzyme-based biosensors have the potential to directly detect extracellular concentrations of glutamate in brain tissue with a high spatial and temporal resolution. To optimize their analytical performance, much attention has been paid to the architectural construction of these biosensors. In particular, the coupling of enzymes to the electrode surface has received much interest, which has resulted in many (derivatives of) first-, second-, and third-generation type of biosensors. However, it is remarkable that in the literature little attention, if any, has been paid to the influence of the quality of the enzyme itself on the analytical performance of a biosensor. Previously we have reported that different batches of ascorbate oxidase significantly altered the performance of our glutamate microsensor.(1) In this note, it is shown that a simple enzyme purification procedure as buffer exchange leads to a more uniform enzyme quality and also significantly improves the reproducibility and performance of the microsensor. In our opinion, this is an important observation and of general interest for the construction of enzyme-based biosensors.