title: Cholesterol biosensors prepared by layer-by-layer technique.
abstract: The analysis of formation, deposition and characterization of cholesterol oxidase (COX) layer-by-layer films were performed. Initially, a layer of polyanion, poly(styrene sulfonate) (PSS) was adsorbed followed by a layer of polycation, poly(ethylene imine) (PEI) on each solid substrate from aqueous solutions. The alternating layers were formed by consecutive adsorption of polycations (PEI) and negatively charged proteins (COX) and cholesterol esterase (CE). A strong interaction between protein and polyelectrolyte improves the stability of the alternating multilayer; however, it can change a native protein conformation and impair the protein activity. The PSS/PEI/COX, PSS/PEI/COX/PEI/CE, PSS/PEI/COX-CE/PEI etc. layered structures were prepared on the surface of a platinum electrode, ITO coated glass plate, quartz crystal microbalance, quartz plates, mica and silicon substrates. Optical and gravimetric measurements based on an ultraviolet-visible absorption spectroscopy and a quartz crystal microbalance revealed that the enzyme multilayers thus prepared consist of molecular layered of the proteins. The surface morphology of such bilayer films was investigated by using atomic force microscopy. The electrochemical redox processes of the enzyme-layered films deposited either on platinum or ITO coated glass plate were investigated. The response current of cholesterol oxidase electrode with concentration of cholesterol was investigated at length.
authors.affiliation: Polo Nazionale Bioelettronica, Corso Europa 30, 16132 Genoa, Italy.
authors.forename: M K
authors.initials: MK
authors.lastname: Ram
authors.forename: P
authors.initials: P
authors.lastname: Bertoncello
authors.forename: H
authors.initials: H
authors.lastname: Ding
authors.forename: S
authors.initials: S
authors.lastname: Paddeu
authors.forename: C
authors.initials: C
authors.lastname: Nicolini
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002784:Cholesterol / Q000032:analysis*; D002789:Cholesterol Oxidase; D004563:Electrochemistry; D004800:Enzymes, Immobilized; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D011094:Polyethyleneimine; D011137:Polystyrenes; D011791:Quartz; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D002787:Sterol Esterase
chemical_list: D004800:Enzymes, Immobilized; D011137:Polystyrenes; D011791:Quartz; C003321:polystyrene sulfonic acid; D011094:Polyethyleneimine; D002784:Cholesterol; D002789:Cholesterol Oxidase; D002787:Sterol Esterase