Design of an Interference-Free Cholesterol Amperometric Biosensor Based on the Electrosynthesis of Polymeric Films of Diaminonaphthalene Isomers

Different cholesterol amperometric biosensors were developed based on entrapment of cholesterol esterase and/or cholesterol oxidase in polymer films of diaminonaphthalene isomers, electrochemically synthesised from aqueous solutions of the monomers and enzymes in phosphate buffer at neutral pH. These conditions permit the growth of films with extraordinary selective properties which allow the preparation of interference-free biosensors for application in biological media without the response being affected by the presence of either endogenous species (ascorbic and uric acid) or exogenous species like 4-acetamidophenol. These selective properties were evaluated for the different monolayer and bilayer configurations proposed in function of the film permeation factor. All the steps involved in the preparation of the biosensors; and determination of free or total cholesterol were carried out in a flow system. A comparative study was made of the analytical properties of each of the configurations developed and their application to the flow-injection determination of cholesterol in a synthetic serum