Choline-sensing electrode based on polyethylene glycol-modified enzyme and mediator

Polyethylene glycol-modified choline oxidase (PEG—ChOD) has been prepared in order to construct choline-sensing carbon-paste electrodes: the PEG—ChOD and mediator, 1,1-dimethylferrocene, are incorporated into a carbon-paste matrix. The PEG—ChOD-based electrode exhibits higher enzyme activity than an electrode using native ChOD, since the PEG is effective in protecting ChOD from oil in the paste. The current response of the PEG—ChOD-based electrode is larger than that of the native ChOD-basedone for choline concentrations higher than 5 mM. The PEG—ChOD-based electrode is more stable than the native ChOD-based one. Coating the surface of the PEG—ChOD-based electrode with a cation polymer is effective in enhancing the current response to choline: the current response of the PEG—ChOD-based electrode coated with a layer of AQ-29D (Kodak) is about four times larger than that of the AQ-29D-free electrode.