Cyclodextrin-modified biosensors: comparision of cyclodextrin-linked ferrocenes as mediators in sol–gel and screen-printed formats for sensing acetylcholine

Abstract

This work reports the comparison of a sol–gel and a screen-printed biosensor format using new mediators and a sensitive thin-film (: P. Kataky and D. Parker, Analyst, 1996, 121, 1829) to enhance the sensitivity and stability of biosensors. The new mediators were per-alkylated cyclodextrin linked ferrocenes and a control, ferrocene aminocarboxylic acid. The thin film comprised a cocktail with polyurethane, plasticiser, lipophilic anion and a perethylated β-CD. The analyte targeted was acetylcholine using the established horseradish peroxidase–choline–oxidase–acetylcholine esterase relay. The screen-printed electrode format showed a marked decrease in oxidation potential, the magnitude of the shift depended on the structure of the mediator and the membrane covering. Although lower oxidation-potentials were observed with the sol–gel format sensors, their response was more akin to aqueous solution behaviour. Electrocatalytic currents were observed suggesting a highly efficient electron transfer process.