CLINICAL ANALYSIS OF UREA IN HUMAN BLOOD BY COUPLING A SURFACE-ACOUSTIC-WAVE SENSOR WITH UREASE EXTRACTED FROM PUMPKIN SEEDS

A surface acoustic wave (SAW) urease sensor system was developed in wh ich a SAW resonator oscillating at 61 MHz and a pair of parallel elect rodes were utilized by coupling with urease extracted from pumpkin see ds. The Michaelis constant and the maximum reaction rate of urease wer e estimated as 2.08 X 10(-3) mol/l and 8.85 kHz/min, respectively, at pH 7.5 and 25.0 degrees C. The analytical characteristics of the ureas e sensor system, including influences of pH, temperature on frequency response, calibration curves, reproducibility, selectivity over enzyma tic interferences were determined. The recovery of the sensor system r anged from 96 to 105% and the experimental detection limit of urea was 0.50 mu g/ml (i.e., 8.3 X 10(-6) M, S/N = 3). The SAW urease sensor s ystem possesses the characteristics of good reproducibility and specif icity. It has been successfully applied to the analysis of urea in hum an blood samples. The assay results are consistent with the results te sted by conventional colorimetry and also support clinical diagnosis.