Uric Acid Sensor with Immobilized Uricase Using Oxirane Acrylic Beads as Supporting Material

Abstract

Uricase was immobilized on oxirane acrylic beads to attain stabilized activity of uricase. The immobilized uricase particles were packed in a micro bed (5.5 mm in dia. and 1.55.0 mm in depth) and attached to the top of a dissolved oxygen sensor of galvanic type. The concentration response characteristics and the stability of the sensor were studied for uric acid concentrations of 010 mg/dl in 50 mM tris borate buffer solution of pH 8.5 at a temperature of 1535°C. The results are summarized as follows.
1) Dynamic response of the sensor to stepwise change of uric acid concentration was approximately expressed by an equation of first-order response. The dead time was 0.10.68 min and the constant was 0.180.6 min. 2) Steady-state response of the sensor was proportional to the uric acid concentration up to 2.53 mg/dl. 3) When it was stored in the buffer solution at room temperature while not used, the sensor showed stable response within ±5% fluctuation for 250 days and more. 4) The slope of the linear correlation of sensor response with uric acid concentration was shown theoretically and experimentally to be inversely proportional to the dissolved oxygen concentration.