Marchenko S. Development of enzyme biosensor system for simultaneous determination of urea and creatinine

The thesis is dedicated to the development and optimization of two potentiometric enzyme biosensors based on immobilized hydrolases for urea and creatinine determination; these biosensors were finally combined into a biosensor system for simultaneous determination of these substances. The urea biosensor contained recombinant urease for widening linear range of determination. This biosensor was applied for the first time for measurements in real medical samples. As a result of the research the laboratory prototypes of potentiometric monobiosensors and biosensor system have been developed. A composition of the biosensors bioselective membranes has been optimized. Analytical characteristics of the biosensors have been evaluated and optimized. Effects of the parameters of working solution (pH, buffer capacity and ionic strength) and different storage conditions on the functioning of biosensors have been investigated. The concentrations of urea and creatinine in human blood serum and post-dialysate samples (taken from the patients with renal failure) were measured using the biosensors. The results of measurements correlated well with obtained by traditional methods of urea and creatinine determination. The developed laboratory prototype of biosensor system can be a prospective basis for construction and industrial production of commercial measuring devices for medical purposes.