AMPEROMETRIC BIOSENSOR BASED ON CARBON-PASTE MIXED WITH ENZYME, LIPID AND CYTOCHROME-C

The electrochemical behavior of horse heart cytochrome c has been investigated at several lipid-containing carbon paste electrodes (CPEs). Cytochrome c showed no electroactivity in the CPE but its redox behavior was observed when the CPE contained judiciously selected lipids. Rapid electron transfer was obtained by incorporating negatively charged lipids into the electrode matrix. A reagentless L-lactate CPE modified with cytochrome c, asolectin and lactate dehydrogenase (cytochrome bz) was developed. The biosensor operated at low potentials (+0.15 V/SCE), avoiding the interference from ascorbate and urate ions. The determination of L-lactate was made in the concentration range 1 mu M-10 mM. After 5 weeks of storage in phosphate buffer (pH 7.4) at 4 degrees C, 30% of the original sensor response remained.