Improved mediated tyrosinase amperometric enzyme electrodes

Tyrosinase amperometric enzyme electrodes in a carbon paste configuration based on the electroreduction of quinoid enzymatic products have been constructed. The electroreduction was mediated by the inclusion in the carbon paste material of an osmium (4,4'-dimethyl 2,2'-bipyridine)(2)(1,10-phenanthroline-5,6-dione) mediator. The mediated electrodes showed a three-fold increase in current density, almost two orders of magnitude decrease in detection limit, and a more than one order of magnitude increase in lifetime of the sensor under FIA conditions compared with the unmediated electrodes. Furthermore, they showed a clear mass transport limited response, changing the response limiting step compared with unmediated electrodes. These findings suggest that the use of suitable mediators and electrode configurations can improve the characteristics of tyrosinase electrodes.