title: Phospholipid-sepiolite biomimetic interfaces for the immobilization of enzymes.
abstract: Biomimetic interfaces based on phosphatidylcholine (PC) assembled to the natural silicate sepiolite were prepared for the stable immobilization of the urease and cholesterol oxidase enzymes. This is an important issue in practical advanced applications such as biocatalysis or biosensing. The supported lipid bilayer (BL-PC), prepared from PC adsorption, was used for immobilization of enzymes and the resulting biomimetic systems were compared to several other supported layers including a lipid monolayer (ML-PC), a mixed phosphatidylcholine/octyl-galactoside layer (PC-OGal), a cetyltrimethylammonium monolayer (CTA), and also to the bare sepiolite surface. Interfacial characteristics of these layers were investigated with a focus on layer packing density, hydrophilicity/hydrophobicity, and surface charge, which are being considered as key points for enzyme immobilization and stabilization of their biological activity. Cytoplasmic urease and membrane-bound cholesterol oxidase, which served as model enzymes, were immobilized on the different PC-based hybrid materials to probe their biomimetic character. Enzymatic activity was assessed by cyclic voltammetry and UV-vis spectrophotometry. The resulting enzyme/bio-organoclay hybrids were applied as active phase of a voltammetric urea biosensor and cholesterol bioreactor, respectively. Urease supported on sepiolite/BL-PC proved to maintain its enzymatic activity over several months while immobilized cholesterol oxidase demonstrated high reusability as biocatalyst. The results emphasize the good preservation of bioactivity due to the accommodation of the enzymatic system within the biomimetic lipid interface on sepiolite.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Bernd
authors.initials: B
authors.lastname: Wicklein
authors.forename: Margarita
authors.initials: M
authors.lastname: Darder
authors.forename: Pilar
authors.initials: P
authors.lastname: Aranda
authors.forename: Eduardo
authors.initials: E
authors.lastname: Ruiz-Hitzky
mesh_terms: D000327:Adsorption; D001426:Bacterial Proteins / Q000737:chemistry*; D032701:Biomimetics / Q000295:instrumentation*; D001951:Brevibacterium / Q000201:enzymology*; D032449:Canavalia / Q000201:enzymology; D002789:Cholesterol Oxidase / Q000737:chemistry*; D004800:Enzymes, Immobilized / Q000737:chemistry*; D017633:Magnesium Silicates / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D013499:Surface Properties; D014510:Urease / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D004800:Enzymes, Immobilized; D017633:Magnesium Silicates; D010743:Phospholipids; D010940:Plant Proteins; C001671:magnesium trisilicate; D002789:Cholesterol Oxidase; D014510:Urease