Covalent Immobilization of Urease on Poly(Pyrrole-3-carboxylic Acid): Electrochemical Impedance and Mott Schottky Study

Abstract

Pyrrole-3-carboxylic acid was electropolymerized on a glassy carbon electrode in 0.1 M NaClO4/ACN, Et4NBF4/ACN using cyclic voltammetry. Urease (Urs) was immobilized onto PPCA modified GCE via covalent binding, exploiting EDC/NHS chemistry. Electrochemical impedance spectroscopy was used to investigate the interfacial behavior of Urs immobilized PPCA surfaces at open circuit potential. The impedance spectra were fitted before and after immobilization of Urs using equivalent circuits of R(C(R(Q(RW)))). After immobilization of Urs onto the PPCA matrix, the charge transfer resistance (R-CT) increased for electrodes, which R-CT of urease immobilized PPCA-NaClO4 matrixes were lower than that of the Urs immobilized PPCA-Et4NBF4 matrixes indicating higher charge transfer ability. A decrease in double layer capacitance (C-dl) values when Urs was immobilized at the PPCA-NaClO4 electrode surface was observed, whereas an increase at the PPCA-Et4NBF4 electrode surface was observed. Urs immobilized electrodes resulted in a n-type semiconducting behavior revealing a positive slope. An increase in acceptor concentration of the electrodes, and a shift of the E-FB to more positive values with increasing amount of urease was observed. The Urs based electrode (PPCA-NaClO4-Urs) was used for detection of urea, which was detected in range of 0.9 to 14 mM with a detection limit (LOD) of 8.28 mu M. (C) 2016 The Electrochemical Society. All rights reserved.