Electrochemical sensor for measurement of urea and creatinine in serum based on ac impedance measurement of enzyme-catalyzed polymer transformation

Enzyme-catalyzed polymer transformation with electrochemical ac impedance d etection has been employed for the measurement of urea and creatinine in se rum samples. A polymer, based on poly(methylvinyl ether)/maleic anhydride m odified by esterification with n-octanol, which is stable at pH 7.4 and whi ch is transformed rapidly in response to alkaline pH changes, was linked to enzymatic reactions between urease and urea or creatinine deiminase and cr eatinine to produce a disposable sensor system. The polymer was screen-prin ted onto interdigitated screen-printed carbon electrodes and the electrodes overlaid with absorbent pads containing the relevant enzyme. Application o f serum samples, "spiked" with either urea or creatinine, resulted in rapid polymer transformation, and resultant changes in the capacitance of the po lymer-coated electrodes were analyte-concentration dependent. Additional in formation on the mechanisms of polymer transformation was obtained from dyn amic quartz crystal microbalance measurements.