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    Monomolecular films of cholesterol oxidase and S-Layer proteins

    Year: 2011

    Journal: Applied Surface Science, 2011, 257 (15), 6535-6539, 20131009

    Authors: Helen Conceição Ferraz, Juliana Aguilar Guimarães, Tito Livio Moitinho Alves, Carlos José Leopoldo Constantino

    Organizations: Chemical Engineering Program, Universidade Federal do Rio de Janeiro, Caixa Postal 68502, Rio de Janeiro, RJ 21941-972, Brazil; Department of Physics, Chemistry and Biology, Universidade Estadual Paulista Júlio de Mesquita Filho, Caixa Postal 467, Presidente Prudente, SP 19060-900, Brazil

    Cholesterol oxidase (ChOx) is a flavoenzyme that catalyzes the oxidation of cholesterol to cholest-5-en-3-one and subsequently the isomerization to cholest-4-en-3-one. ChOx has been very commonly studied as the detection element in cholesterol biosensors. In the biosensor development field, a relatively new approach is the use of crystalline bacterial cell surface layers, known as S-Layer proteins. These proteins exhibit the ability of self-assembling at surfaces, opening a vast spectrum of applications, both in basic and applied researches. In our study, monomolecular films of ChOx and mixed films of ChOx/S-Layer proteins and DPPC/S-Layer proteins were produced using the Langmuir technique. Characterization of the films was performed by means of surface pressure–molecular area (π–A) isotherms. Stable monolayers were obtained, which means that they can be transferred to solid substrates by Langmuir–Blodgett technique. Mixed monolayers showed an ideal like behavior.