A Conductometric Urea Biosensor by Direct Immobilization of Urease on Pt Electrode

Abstract

<em>Urease was immobilized on platinum electrode both by chemical binding and electropolymerization.The conductometric urea </em><em>biosensor thus prepared showed a detection limit of 4.9×10^-5 M and linear dynamic range from 4.9×10^-5 to 5.8×10^-3M for urea concentration when the enzyme is covalently immobilized on Pt electrodes. Conductometric transducers respond to the changes </em><em>in ionic </em><em>strength thereby leading to </em><em>uncontrolled inaccuracies. </em><em>Such </em><em>interferences </em><em>were </em><em>effectively suppressed by here the use of differential sensor pairs. It was shown that measurements in diluted fluids are possible with the use of a</em><em>reference sensor having no </em><em>immobilized enzyme.</em><em>Specifically, the sensor constructed by covalent binding provided more reproducible responses than that prepared by electropolymerization. Namely the former preserved 80% of its initial activity over a period of 25 </em><em>days. </em><em>In order </em><em>to </em><em>provide </em><em>more reproducibility,</em><em>a method </em><em>was </em><em>developed </em><em>for regeneration of the sensor surface so that, the renewed sensor would responded to urea almost as new.</em>