Characterization of immobilized urease membrane on silicon nitride layer

Abstract

Quantitative characterization of an organic thin membrane containing immobilized urease was obtained by using a piezoelectric quartz crystal with a silicon nitride (Si 3N 4) layer, and the surface state of the organic thin membrane investigated by FTIR (Fourier Transform Infrared Spectroscopy). A silicon nitride layer was sputtered onto the surface of a silver electrode plated on a piezoelectric quartz crystal. The relationship between frequency change and surface mass change on the piezoelectric quartz crystal with the silicon nitride layer was investigated by using urease as a standard additive. A linear relationship between frequency change and surface mass change was obtained over the range 50 – 200μg. The sensitivity to surface mass change was approximately -43 KHz mg −1 urease. As a result of these experiments, it is seen that a piezoelectric quartz crystal with a silicon nitride layer can be used as a microbalance. The mass of an organic thin membrane consisting of γ-aminopropyltriethoxysilane and glutaraldehyde plus immobilized urease on a silicon nitride layer was investigated using a piezoelectric quartz crystal with a silicon nitride layer. These values were 12.1 and 1.2μg cm −2 respectively. The thickness of this organic thin membrane is 11 –13 nm. By FTIR Spectroscopy, the absorption band of the amino, methylene and aldehyde groups in organic thin membranes was observed. Immobilized urease activity in this organic thin membrane formed on the piezoelectric quartz crystal coated with a silicon nitride layer was 38 ng urea min −1 cm −2.