Screen-printed electrodes for miniaturization of electrochemiluminescence-based optical biosensors involving oxidases

Screen-printed electrodes are used for miniaturization of an electrochemiluminescent optical choline biosensor used in a batchwise system. Choline oxidase is immobilized on the working electrode surface by ionic interactions with DEAE (diethylaminoethyl)-Sepharose beads before entrapment in a poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) photocrosslinked polymer. A fiber optic faces the sensing layer and is connected to the photomultiplier tube of a luminometer. The influence of buffer pH and composition is studied and shows that these screen-printed electrodes can be used either as disposable devices in 0.2 M carbonate buffer pH 9.5 or as reusable devices (ca. 25 assays) in 30 mM veronal-HCl buffer pH 9.5. Working with veronal buffer containing 50 μM luminol, the linear range for choline extends from 4×10^-8 M to 2×10^-4 M (log-log representation)