Simple routine assay for serum urea using immobilized urease

Area of Science:

• Biochemistry
• Analytical Chemistry
• Enzyme Assays

Background:

• Urea is a key metabolic byproduct and a crucial analyte in clinical diagnostics.
• Accurate and efficient methods for urea quantification are essential for patient monitoring.
• Existing spectrophotometric methods can be time-consuming and require manual sample handling.

Purpose of the Study:

• To develop and validate a rapid, automated assay for serum urea determination.
• To evaluate the performance characteristics of an enzyme thermistor-based urea assay.
• To compare the results of the novel assay with a conventional spectrophotometric method.

Main Methods:

• Immobilization of urease enzyme onto controlled pore glass beads.
• Utilizing an enzyme thermistor unit within a continuous flow system for real-time heat measurement.
• Degradation of urea by immobilized urease, generating a measurable heat signal.
• Systematic investigation of assay parameters including flow rate, linearity, recovery, and interference.

Main Results:

• The assay demonstrated high precision with within-day coefficient of variation (C.V.) of 0.8% and day-to-day C.V. of 3.0% over 56 days.
• Assay time per sample was rapid, requiring only 2-3 minutes from a stand-by state.
• Excellent correlation (coefficient of correlation = 0.991) was observed between the enzyme thermistor results and a standard spectrophotometric method.
• The method showed good linearity, recovery, and minimal interference from common substances.

Conclusions:

• The developed enzyme thermistor assay provides a fast, precise, and accurate method for routine serum urea analysis.
• This automated system minimizes manual intervention and offers significant time savings compared to conventional methods.
• The high correlation with spectrophotometry validates its reliability for clinical diagnostic applications.