Determination of serum glucose using co-immobilized glucose oxidase and peroxidase onto arylamine glass beads affixed on a plastic strip

Glucose oxidase (GOD) from Aspergillus niger and horseradish peroxidase (POD) were co-immobilized onto arylamine glass beads affixed on a plastic strip with a conjugation yield of 28.2 mg/g and 43% retention of their initial specific activity. The coimmobilized enzymes showed maximum activity at pH 7.5 when incubated at 37 degrees C for 15 min. A simple, specific and sensitive method for discrete analysis of the serum glucose was developed employing this strip. The minimum detection limit of the method was 5 mg/dl. Within and between assay coefficient of variations for the serum were <5.6% and <10.6% (n = 6) respondely. A good correlation (r = 0.943) was found between the glucose values obtained by the enzyme colorimetric method employing free GOD and POD and the present method. The strip lost 50% of its initial activity after its 150 regular uses for a period of one month, when stored in reaction buffer at 4 degrees C. The method is cost-effective than the enzymic colorimetric method, as the enzyme strip is reusable.