The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity
McMahon, Colm P.; Rocchitta, Gaia; Serra, Pier A.; Kirwan, Sarah M.; Lowry, John P.; O'Neill, Robert D.; McMahon Colm P.; UCD School of Chemistry and Chemical Biology, University College Dublin; Rocchitta Gaia; UCD School of Chemistry and Chemical Biology, University College Dublin; UCD School of Biomolecular and Biomedical Sciences, University College Dublin; Serra Pier A.; UCD School of Chemistry and Chemical Biology, University College Dublin; UCD School of Biomolecular and Biomedical Sciences, University College Dublin; Kirwan Sarah M.; UCD School of Chemistry and Chemical Biology, University College Dublin; Lowry John P.; UCD School of Biomolecular and Biomedical Sciences, University College Dublin; O'Neill Robert D.; UCD School of Chemistry and Chemical Biology, University College Dublin
Журнал:
Analyst
Дата:
2006
Аннотация:
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<sup>â 2</sup> µM<sup>â 1</sup> 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.
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