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

This work reports the comparison of a sol-gel and a screen-printed biosenso r format using new mediators and a sensitive thin-film (ref. 1: P. Kataky a nd D. Parker, Analyst, 1996, 121, 1829) to enhance the sensitivity and stab ility of biosensors. The new mediators were per-alkylated cyclodextrin link ed ferrocenes and a control, ferrocene aminocarboxylic acid. The thin film comprised a cocktail with polyurethane, plasticiser, lipophilic anion and a perethylated beta -CD. The analyte targeted was acetylcholine using the es tablished horseradish peroxidase-choline-oxidase-acetylcholine esterase rel ay. The screen-printed electrode format showed a marked decrease in oxidati on potential, the magnitude of the shift depended on the structure of the m ediator 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 suggest ing a highly efficient electron transfer process.