Amperometric Glucose Biosensors Based on Glassy Carbon and SWCNT- Modified Glassy Carbon Electrodes

Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochem. activation at +1.80 V (vs. SCE) for 900 s, were used with the aim of comparing their performances in the development of enzyme electrodes. Com. SWCNTs were pretreated with 2.2 M HNO3 for 20 h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors was confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solns. of 0.1 M phosphate buffer (pH 5.5), contg. dissolved oxygen, at a potential of -0.40 V vs. SCE. Although the performances of the 2 carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addn., the prepn. procedure of such biosensors was more simple, rapid and reproducible. Furthermore, activated GC/GOx electrodes were applied to the anal. of a sample of blood serum providing accurate results. On the contrary, the results obtained with SWCNT-GC/GOX electrodes gave a systematic relative deviation of about +20%.