Design of a Multilayer Cholesterol Amperometric Biosensorfor Preparation and Use in Flow Systems (original) (raw)

A cholesterol amperometric biosensor based on a multilayer con®guration with an initial platinized layer electrodeposited on the electrode surface and two sequentially electrosynthesized polymer layers was developed. The polymer bilayer was formed by an inner polypyrrole layer, in which cholesterol oxidase was entrapped, and an outer layer of poly(o-phenylenediamine). All biosensor preparation steps and the determination of the substrate were carried out in a¯ow system, which permitted acceptable reproducibility of the fabrication process of each biosensor. The resulting biosensor, with a detection process based on the electrochemical oxidation at +0.5 V(vs. AgaAgCl) of the enzymatically produced hydrogen peroxide, displayed high ef®cacy in the signal generation process (above 97 %) and had a stable response period of approximately one month. The presence of the two polymer layers had no incidence on the response time (t 95 8 s) and sensitivity and the detection limit are 62 nA mM À1 and 12 mM, respectively. The characteristics of the biosensor were compared to those of other biosensors with a more simple con®guration, which con®rmed the considerable advantages of the biosensor developed. The combined permselective properties of the two polymer layers permitted satisfactory determination of the cholesterol content in reference synthetic serum samples.