Glutamate Dehydrogenase-Based Electrochemical Biosensors: The Immobilization Method Defines Sensor Selectivity

Enzyme-based electrochemical sensors are important tools for the detection of numerous analytes of biological origin. The immobilization of enzymes onto electrodes is a critical step during the fabrication of these devices. Herein, we report the fabrication of glutamate dehydrogenase (GDH)-based biosensors using two different strategies, and the effect of the immobilization method on the performances of obtained bioelectrodes. The first method consisted in cross-linking GDH on the surface of electrodes with glutaraldehyde. The as obtained biosensors presented numerous drawbacks including (i) the complete loss of enzyme selectivity, and (ii) the impossibility to reutilize the bioelectrode for sensing. As an alternative fabrication protocol, GDH was entrapped within a SOL-GEL matrix formed on the surface of electrodes. With this immobilization method the enzyme's specificity was preserved, and the biosensor displayed fast and reproducible electrochemical signals. With this study we raise the attention on the fact that the well-established glutaraldehyde-based cross-linking method can result an aggressive immobilization approach that may harm enzyme specificity, in contrast to the milder SOL-GEL entrapment. (c) 2019 The Electrochemical Society.