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 which a SAW resonator oscillating at 61 MHz and a pair of parallel electrodes were utilized by coupling with urease extracted from pumpkin seeds. The Michaelis constant and the maximum reaction rate of urease were estimated as 2.08 × 10 −3 mol/1 and 8.85 kHz/min, respectively, at pH 7.5 and 25.0 ° C. The analytical characteristics of the urease sensor system, including influences of pH, temperature on frequency response, calibration curves, reproducibility, selectivity over enzymatic interferences were determined. The recovery of the sensor system ranged from 96 to 105% and the experimental detection limit of urea was 0.50 μg/ml (i.e., 8.3 × 10−6 M, SN = 3). The SAW urease sensor system possesses the characteristics of good reproducibility and specificity. It has been successfully applied to the analysis of urea in human blood samples. The assay results are consistent with the results tested by conventional colorimetry and also support clinical diagnosis.