Urea biosensor based on PANi(urease)-Nation®/Au composite electrode

The polyaniline (PANi)-Nafion(R) composite film was prepared onto the ceramic plate by the cyclic voltammetry (CV) method with the various cycle numbers. When the PANi-Nafion(R)/Au/ceramic plate with the preparing cycle number of 5 was as working electrode, the cathodic peak current was achieved as 84.0 muA in 60 mg dl(-1) NH4Cl buffer solution. On the other hand, the small cathodic peak currents for buffer solution in the presence of 60 mg dl(-1) LiOH, NaCl and KCl, respectively, were found with the same composite electrode as working electrode. The cathodic peak current decreased from 84.0 to 16.3 muA in the 60 mg dl(-1) NH4Cl buffer solution when the cycle number for preparing PANi-Nafion(R)/Au/ceramic plate composite electrode with the CV method increased from 5 to 15. The enzyme of urease was immobilized onto the PANi-Nafion(R)/Au/ceramic plate composite film by the electrochemical immobilization and the casting methods and used as sensing electrode to detect the concentration of urea in the buffer solution. The sensitivity of composite electrode immobilized with the casting method was greater than that of electrochemical immobilization method. The sensitivity and the detecting limit of the urea sensor were found to be 0.7 and 5.27 muA (mg dl(-1))(-1) cm(-2), as well as 6 and 0.3 mg dl(-1), respectively, when urease was immobilized by glutaraldehyde (GA) cross-linker and Nafion(R) network, respectively. (C) 2004 Elsevier B.V. All rights reserved.