Biosensor for Measurement of Urea
Tech ID: 11209 / UC Case 1999-004-0
Automated Biosensor for Measurement of Urea and Other Biochemicals
Urea is often measured in blood, serum, and urine in order to assess renal function or for control of artificial dialysis. Urea is also routinely measured in cow milk to determine the efficiency of nitrogen conversion in the diet, leading to substantial reduction in feed costs and waste nitrogen to the environment.
University of California, Davis researchers have invented an improved method for measuring urea that is simple, robust, and inexpensive. The method involves the enzymatic hydrolysis of urea and the subsequent measurement of CO2 partial pressure.
The UC biosensor has a linear sensitivity to urea and has been demonstrated to measure urea nitrogen accurately to within 0.5 mg/dl (0.15 mM) in the physiological range up to 30 mg/dl (10.5 mM). It is projected that the sensor can measure urea accurately to beyond 1 M. The instrumentation on a manually operated version of the sensor costs less than $50, with a reagent cost of less than $0.05 per assay. The process can be automated to perform a measurement of urea in less than 5 min.
Because the sensor measures change in pressure, the method may be modified to measure any analyte which can be converted to a dissolved gas. These include uric acid, which is a significant source of nitrogen runoff from poultry operations, or any of various carbohydrates which can be metabolized to CO2. The method may also be adapted to measure any enzyme generating a dissolved gas. Urease, which hydrolyzes urea, is produced prodigiously by the ulcer causing bacterium Helicobacter pylori and may be used to diagnose an infection by that organism. Identification of ureases in soils is important because they cause rapid volatilization of urea applied to fields. Many enzymes in the citric acid cycle and other metabolic pathways are important clinically for diagnosing different nutritional disorders.
While the new method currently operates as a batch process, a modification may be made whereby it may be operated on a continuous solution stream. In any case it can be automated to run on-line, in the milking parlor for example, to eliminate problems and costs associated with manual sampling and transport to a laboratory for analysis. Because the method involves no toxic chemicals, there is no significant danger of using it for farm, food, or pharmaceutical applications.
The new system promises to be a practical method to measure urea and other important biochemicals in a wide variety of media, including raw milk, whole blood, and industrial slurries.
One distinct advantage of the new method is that the sensing element does not come into direct contact with the solution under test, and therefore it is not susceptible to physical fouling or non-specific interferences from complex media such as raw milk or whole blood. In contrast, most existing technologies require pretreatment schemes such as dialysis which can be complicated, slow, and expensive.
|United States Of America||Issued Patent||6,287,851||09/11/2001||1999-004|
- BonDurant, Robert H.
- Delwiche, Michael J.
- DePeters, Edward J.
- Jenkins, Daniel M.
biosensor, urea biosensor, milk urea