A POLYMERIC BILAYER CONFIGURATION FOR A CHOLESTEROL AMPEROMETRIC BIOSENSOR BASED ON THE COMBINATION OF OVEROXIDIZED POLYPYRROLE AND A POLYNAPHTHALENE DERIVATIVE

ABSTRACT A polymeric hetero-bilayer configuration for a cholesterol amperometric biosensor based on the combination of overoxidized polypyrrole and the electrosynthesized poly(1,5-diamino-polynaphthalene) (P(1,5-DAN)) derivative was developed for the construction of a cholesterol biosensor. The enzyme cholesterol oxidase was entrapped within the inner polypyrrole layer and the P(1,5-DAN) outer layer enhanced the selectivity (by hindering diffusion of electroactive species towards the electrode) and sensitivity (by preventing diffusion of the enzymatically produced hydrogen peroxide towards the bulk solution). The sensitivity and detection limit of the biosensor were 44.99 nA mmol−1 l and 9.7 µmol l−1, respectively. Preliminary tests were carried out to study and compare the electropolymerizing characteristics of three monomers derived from naphthalene, as were 5-amino-1-naphthol (5A1N), 1,8-diaminonaphthalene (1,8-DAN) and 1,5-diaminonaphthalene (1,5-DAN). All the steps involved in the fabrication of the biosensor and the determination of cholesterol were performed in a flow system. The combined permselective properties of the two polymeric layers permitted satisfactory determination of the cholesterol content in reference synthetic serum samples.