Screen-printed electrodes as disposable or reusable optical devices for luminol electrochemiluminescence

Screen-printed electrodes are used to trigger luminol electrochemiluminescence at 450 mV versus printed Ag/AgCl. Choline oxidase (ChOD) is immobilized on the working electrode surface by ionic interactions with a diethylaminoethyl (DEAE) modified polymer (Sepharose or dextran) before entrapment in a poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) photocrosslinked matrix. A fiber optic faces the electrode and is connected to the photomultiplier tube of a luminometer. The effect of the working conditions is studied, in terms of buffer nature and pH. DEAE-Sepharose-based 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. The use of DEAE-dextran instead of DEAE-Sepharose allows to easily control the amount of deposited ionic polymer, but the operational stability of the sensors is decreased (ca. seven assays).