Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/150077

Title

Thin films of polyelectrolyte-encapsulated catalase microcrystals for biosensing

Author(s)

Yu, Aimin;  Caruso, Frank

Abstract

Polyelectrolyte (PE)-encapsulated catalase microcrystals were assembled onto gold electrodes by their sequential deposition with oppositely charged PEs, utilizing electrostatic interactions to form enzyme thin films for biosensing. The PE coating around the microcrystals provided a regular surface charge, thus facilitating the stepwise film growth, and it effectively prevented catalase leakage from the assembled films. The encapsulated catalase was shown to retain both its biological and its electrochemical activity. Direct electron transfer between catalase molecules and the gold electrode was achieved without the aid of any electron mediator. In pH 5.0 phosphate buffer solution, the apparent formal potential (E-o') of catalase was -0.131 V (vs Ag/AgCl). As a H2O2 biosensor, films consisting of one layer of the encapsulated catalase displayed considerably higher (similar to5-fold) and more stable electrocatalytic responses to the reduction of H2O2 than did corresponding films made of one layer of nonencapsulated catalase or solubilized catalase. An increase in either the number of "precursor" PE layers between the gold electrodes and the catalase microcrystal layers in the film or the number of PE layers encapsulating the catalase microcrystals was found to decrease the electrocatalytic activity of the electrode. At low precursor PE layer numbers (similar to2) and PE encapsulating layers (similar to4), the current response was proportional to the H2O2 concentration in the range 3.0 x 10(-6) to 1.0 X 10(-2) M. The overall electroactivity of the multilayer film increased for the first two layers of encapsulated catalase, after which a plateau was observed. This was attributed to the increasing difficulty of electron transfer and substrate diffusion limitations. The current approach of using immobilized PE-encapsulated enzyme microcrystals for biosensing provides a versatile method to prepare high enzyme content films with high and tailored enzyme activities.

Publication type

Journal article

Source

Analytical Chemistry, Vol. 75, no. 13 (Jul 2003), pp. 3031-3037

Publication year

2003

FOR Code(s)

0301 Analytical Chemistry;  0904 Chemical Engineering

Keyword(s)

By-layer adsorption;  Crystal microbalance electrodes;  Cytochrome-C;  Direct electrochemistry;  Enzyme multilayers;  Lipid films;  Methylene-blue;  Particles;  Protein multilayer films;  Voltammetry

Publisher

American Chemical Society

ISSN

0003-2700

Publisher URL

http://dx.doi.org/10.1021/ac0340049

Copyright

Copyright © 2003 American Chemical Society. The American Chemical Society does not allow Swinburne researchers to archive either the accepted manuscript or the published version of the article.

Peer reviewed