Enzyme Activity Preservation for Galactose Oxidase Immobilized in Stearic Acid Langmuir-Blodgett Films

Abstract The adsorption of the enzyme galactose oxidase onto stearic acid Langmuir monolayers was investigated with surface pressure-area isotherms, Brewster Angle Microscopy and polarization-modulated infrared reflection-absorption spectroscopy. The enzyme was incorporated in the monolayer at low surface pressures, expanding the lipid films, and further monolayer compression expelled it from the contact with the air phase and repositioned the enzyme below the lipid polar heads. The enzyme-lipid system was then stabilized by electrostatic interactions, leading the monolayer to condense at higher surface pressures, reducing the number of interfacial aggregates. The lipid-enzyme interactions at the interface made the monolayer less viscoelastic and more disordered as pointed by the reduced compressional modulus and decreased trans/gauche ratio for the lipid acyl chains. Also, the secondary structures of the adsorbed enzyme were kept as demonstrated with infrared spectroscopy. The condensed enzyme-lipid monolayer was transferred to solid supports as Langmuir-Blodgett films and the enzyme activity was detected, being preserved for one month. These results show how the molecular organization provided by the ultrathin films can help maintain the catalytic activity for immobilized enzymes, which is important, general speaking, for nanotechnology and biosensing manufacturing.