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The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity

Lowry, John and Mc Mahon, Colm and Rocchitta, Gaia and Serra, Pier and Kirwan, Sarah and O'Neill, Robert (2006) The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity. Analyst, 131. pp. 68-72.

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Abstract

The apparent Michaelis constant, KM, for glutamate oxidase (GluOx) immobilised on Pt electrodes increased systematically with enzyme loading. The effect was due, at least in part, to electrostatic repulsion between neighbouring oxidase molecules and the anionic substrate, glutamate (Glu). This understanding has allowed us to increase the Glu sensitivity of GluOx-based amperometric biosensors in the linear response region (100 ± 11 nA cm–2µM–1 at pH 7.4; SD, n = 23) by incorporating a polycation (polyethyleneimine, PEI) to counterbalance the polyanionic protein. Differences in the behaviour of glucose biosensors of a similar configuration highlight a limitation of using glucose oxidase as a model enzyme in biosensor design.

Item Type: Article
Keywords: Glutamate oxidase; surface enzyme; electrostatic; polycation; biosensor sensitivity;
Subjects: Science & Engineering > Chemistry
Science & Engineering > Institute of Immunology
Item ID: 928
Depositing User: John Lowry
Date Deposited: 13 Mar 2008
Journal or Publication Title: Analyst
Publisher: Royal Society of Chemistry
Refereed: Yes
URI:

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