1.0 - Screen Printed Solid State Contact Biosensors for the Determination of Urea in Undiluted Biological Samples

Abstract

This chapter elaborates the screen printed solid-state contact biosensors for the determination of urea in undiluted biological samples. The concentration of urea in serum, or whole blood is an important index of renal function. A solid state urea biosensor, based on an ammonium ion selective electrode with covalently bound urease, has been developed to determine urea concentrations in undiluted serum, plasma, and whole blood. Screen printing technique has been chosen to produce low cost biosensors with high reproducibility. It is observed that to correct interferences caused by pH, sodium, potassium, and ammonium ions, an additional screen printed NH4+-ISE has been used. It is found that with this type of urea biosensor, it is possible to determine more than 800 serum samples with minimal changes in sensor performance. All measurements have been performed at 37°C at a rate of 60 samples/hour. Slope data have been determined with phosphate buffered solutions at pH 7.4 containing 5 mM KCl, and 150 mM NaCl. General sensor performance data including the ability to determine urea concentrations in undiluted whole blood, and diluted urine are also presented.