Development of novel micro-sensor of disposable chips with oxygen enrichment by pre-electrolysis for monitoring blood glucose

Monitoring blood glucose level is an important procedure for any diabetic s ubject. The blood, however, has oxygen tension less than 5%. Since the oxyg en in the sensor membrane is consumed by the enzyme reaction, the oxygen co ncentration is needed high enough for a better linearity between output cur rent and the glucose concentration. In this monitor, the oxygen is generated by electrolysis of the solution be fore monitoring, and the glucose concentration is monitored by a peak curre nt obtained by a potential sweep method. A theoretical analysis was made co nsidering diffusions of glucose. oxygen and hydrogen peroxide, and also the rate of the two-substrate reaction catalyzed by glucose oxidase (GOD) with in the enzyme membrane. Concentrations within membranes were analysed by a model of three layers of the solution, the overcoat gel and the enzyme memb rane. The output current increased with time after sweeping the potential anodica lly and had its maximum in 10-20 s. The peak current was linearly proportio nal to the glucose concentration up to 500 mg dl(-1) by the supplement of o xygen generated by electrolysis of the solution. The peak current was well simulated by a mathematical model. When one minute is adopted to this monit or, the optimum conditions of M-G, enzyme membrane thickness and electrolys is time were determined to be 1.9-3.8, 4.7-9.4 mu m and 5-10 s, respectivel y. (C) 1999 Elsevier Science Ltd. All rights reserved.