Covalent immobilization of urease on polypyrrole microspheres for application as a urea biosensor

Urease has been covalently immobilized on polypyrrole microspheres chemically linked to conducting polypyrrole-polyvinyl sulfonate (PPY-PVS) films. These films were electrochemically prepared during 5 7 min at a constant current of 2 mA using indium tin oxide (ITO) glass plates as the working electrode, and a standard calomel electrode as the reference electrode. Urease covalently linked to polypyrrole microspheres (by reaction of protein amino groups with aldehyde groups on the surface of the microspheres) was entrapped/adsorbed onto electrochemically prepared conducting PPY-PVS films deposited on ITO. Potentiometric measurements undertaken on these conducting polymer electrodes using an ammonium ion analyzer reveal that they can be used for estimating the urea concentration in solutions from 5·10 mol/l to 6·10 mol/l.