The influence of carbon nanotubes and polyazine redox mediators on the performance of amperometric enzyme biosensors

Biosensors with novel modified electrode structures for glucose determination have been developed by using different combinations of multiwalled carbon nanotubes (CNTs) and polyazine redox polymer, poly(neutral red) or poly(brilliant cresyl blue) on glassy carbon electrodes (GCE). CNT films were formed using functionalised CNTs, covalently immobilised by crosslinking in a chitosan matrix, and the azine dyes were electropolymerised directly on GCE or on top of the GCE modified with CNTs. Glucose oxidase (GOx) was immobilised by crosslinking with glutaraldehyde on top of the GCE modified with CNT, poly(azines), or combinations of poly(azines) and CNT. An assembly with enzyme/nanotube mixture immobilised on top of polyazine films was also studied. The mechanism of functioning was investigated in the presence and absence of oxygen and also by using bienzymatic devices containing glucose oxidase and catalase. Of the combinations studied, the best performance was obtained with a PBCB/CNT/GOx biosensor at a potential of -0.3 V vs. SCE with a detection limit of 11 mu mol L-1.