A layer-by-layer deposition technique was employed for fabricating choline biosensors using chloline oxidase (ChOx) and polycations such as poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA). A platinum electrode was coated with ChOx/PEI or ChOx/PDDA thin film to prepare amperometric choline sensors. The amperometric response of the sensors depended significantly on the type of the polycations. The ChOx/PDDA film suppressed the permeation of choline, resulting in a lower response than that of the ChOx/PEI film-based sensors. The results were rationalized based on the different chemical structures of the polycationic materials.
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