Trueness Assessment for Serum Glucose Measurement Using Commercial Systems through the Preparation of Commutable Reference Materials

BACKGROUND: Commutable reference materials (RMs) are suitable for end-users for evaluating the metrological traceability of values obtained using routine measurement systems. We assessed the performance of 6 routine measurement systems with validated secondary RMs. METHODS: We tested the homogeneity, stability, and commutability of 5 minimally processed human serum pools according to the standard guidelines. The serum pools were assigned values as per the reference procedure of the United States Centers for Disease Control and were used to evaluate the trueness of results from 6 commercial measurement systems based on enzymatic methods: 3 glucose oxidase (GOD) and 3 hexokinase (HK) methods. RESULTS: The prepared RMs were validated to be sufficiently homogenous, stable, and commutable with the patient samples. Method bias varied for different systems: GOD01, -0.17 to 2.88%; GOD02, 1.66 to 4.58%; GOD03, -0.17 to 3.14%; HK01, -3.48 to -0.85%; HK02, -3.83 to -0.11%, and HK03, -1.82 to -0.27%. CONCLUSIONS: We observed that the prepared serum glucose RMs were qualified for trueness assessment. Most of the measurement systems met the minimal quality specifications.

Limitation of glucose oxidase method of glucose estimation in jaundiced neonates.

The most widely used method for estimation of plasma glucose is that adopted by Trinder's using glucose oxidase-peroxidase (GOD-POD) system. This method gives much lower blood glucose values with blood samples of neonatal jaundice (plasma bilirubin level > 10 mg/dL) of age 10 +/- 5 daysthan with samples of neonates of the same age group without jaundice or older children suffering from other diseases like acute respiratory distress, septicemia.

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.

Inmovilización covalente de glucosa oxidasa y peroxidasa / Covalent immobilization of oxidase glucose and peroxidase

Las enzimas por su función catalítica tienen amplia aplicación en infinidad de procesos tecnológicos y en los últimos 15 a han marcado avances significativos en la industria. Dentro de la Industria Farmacéutica y Biológica, la dedicada a los medios diagnósticos ha recibido también el impacto de la introducción de este tipo de productos, soportando en la actualidad tecnologías tan importantes como el inmunoensayo enzimático, el diagnóstico en química clínica y la química seca, donde las técnicas de inmovilización alcanzan un desarrollo cada vez mayor por el incremento de la estabilidad que se logra con estos sistemas. Se presentan ensayos de inmovilización covalente de las enzimas glucosa oxidasa y peroxidasa sobre papel de filtro Whatman No. 2. Fueron ensayadas 2 variantes: la inmovilización covalente de un polímero soluble de las enzimas y la inmovilización covalente de una solución de las enzimas libres. Los resultados del proceso se evaluaron frente a soluciones de referencia de glucosa en concentraciones entre 2,0 y 55,0 mmol/L. Las mejores respuestas se encontraron con el más bajo porcentaje de inmovilización en el caso del enlazamiento del polímero, y para la solución de las enzimas libres correspondió al más alto grado de inmovilización logrado

Effect of ammonium and nitrate ratio on glucose oxidase activity during gluconic acid fermentation by a mutant strain of Aspergillus niger.

Of the factors tested, the source and concentration of carbon and nitrogen in the medium exerted maximum effect on growth and acid production. Glucose (15%) and urea (0.14%) induced glucose oxidase synthesis and optimum yield of calcium gluconate. Potassium dihydrogen phosphate (0.2%) and magnesium sulphate (0.06%) stimulated glucose oxidase activity and calcium gluconate production. Borax at a concentration of 1.5 g/L induced maximum glucose oxidase and calcium gluconate production with increased glucose utilization.

Supports for enzyme immobilization

Macroporous silica gel, prepared from sodium silicate and hydrochloric acid, one grade of diatomaceous earth (celite 545) and nonporous glass were analyzed in terms of pore size by the mercury intrusion pressure method. The alkylamine derivatives of the above materials were examined for their suitability as supports for enzyme immobilization, using the enzyme glucose oxidase. The effectiveness of the immobilized enzyme was compared in relation to the free enzyme and particle size of the carier. The immobilized enzyme exhibited a broader range of optimum pH and greater thermal stability, among some properties considered