Fabrication and Electrochemical Characterization of Nanoporous Silicon Electrode for Amperometric Urea Biosensor

Abstract

We describe a new type of biosensor that employs a modified gold electrode based on nanoporous silicon (NPSi) for the electrochemical detection of urea. Urease (Urs) was covalently immobilized onto an Au/NPSi electrode functionalized with 3-mercaptopropionic acid (3-MPA). Amperometric calibration curves for both NPSi and planar silicon (PLSi)-based urea sensitive electrodes were compared in the range of 0.3 to 4.5 mM urea concentrations. The Michaelis–Menten constant ( K m ) was determined using the amperometric method. The electrochemical active area ( A ea ) of the 3-MPA/Au/NPSi electrode was evaluated using cyclic voltammetry (CV) and the result was compared with the 3-MPA/Au/PLSi electrode. Measured sensitivity of the Urs/SAMs/Au/NPSi electrode is ca. 2.05 µA mM -1 cm -2 and that of the Urs/SAMs/Au/PLSi electrode is ca. 1.10 µA mM -1 cm -2 . About 1.8 times of sensitivity increase is obtained in the Au/NPSi electrode.