UREASE BIOSENSOR ON FIELD-EFFECT TRANSISTOR BASIS DESIGN-FEATURES ANDOPERATING PARAMETERS IN MODEL SOLUTIONS

The characteristics of a biosensor based on a pH-sensitive field-effec t transistor have been studied. In 1 mM potassium phosphate buffer, th e region of proportionality between urea concentration and biosensor r esponse was 0.05-0.5 mM; in 5 mM and 10 mM buffers, the corresponding regions were 0.1-1 mM and 0.25-1.5 mM, respectively. Different factors influencing the biosensor's response were examined: pH, the buffer ca pacity, ionic strength of the solution, and temperature. The stability of urease immobilized in a protein layer was studied during prolonged storage. It was found that the immobilized enzyme loses practically n o activity when stored for one month in EDTA-containing buffer solutio n at 4-degrees-C. The results obtained were discussed with respect to urea analysis in blood