Potentiometric urea biosensor based on urease immobilized by an electrosynthesized poly(o-phenylenediamine) film with buffering capability

A simple and novel potentiometric biosensor for urea detection was prepared by employing an electrosynthesized polymer with buffering capability. It was obtained by deposition of a weighed amount of urease (Ur) at a glassy carbon (GC) electrode followed by immobilization by an electrosynthesized poly-o-phenylenediamine (PPD) film. An unconventional “upside-down” (UD) geometry was employed for the electrochemical cell. The response of GC/Ur/PPD sensor is linear with urea concentration in the range 10 μM to 1 mM (15 mV/mM, R2 = 0.9999) due to buffering capability of PPD film, which represents a novel role of electrosynthesized polymers in their application to biosensors. At higher concentrations, the more common Nernstian response (28 mV/decade, R2 = 0.9987) is observed. The sensor exhibits a sufficient sensitivity for practical determinations, rapid response and long term stability.