Estudo de monocamadas fosfolipidicas nanoestruturadas obtidas por LB para aplicações em biossensores

Abstract

There has been long-standing interest in the physical chemical properties of defined mixtures of cholesterol and phospholipids in monolayer and bilayer membranes. They also provide insight into certain properties of the membranes of animal cells. Even if phospholipids and sphingolipids build up the matrix of cellular membranes, sterols areessential components of these membranes. In contrast to the amazing diversity of phospholipid species, mammalian cells contain one major sterol, cholesterol, which is absolutely required for viability and cell proliferation. The studies of phospholipid monolayers containing cholesterol have the potential to uncover interactions important forunderstanding bilayer membranes. The aim of the present work was to investigate hybrid phospholipids monolayers mixed with cholesterol and bovine serum albumin deposited through Langmuir-Blodgett (LB) films. Phosphatidylcholines with different chain size, DMPC, DPPC and DAPC, monolayers and their hybrids with cholesterol (DPPC/CHOL and DAPC/CHOL), phosphatidylethanolamine (DMPE, DPPE), DPPC/BSA andDPPC/CHOL/BSA monolayers were obtained at water/air interface. Mixtures of cholesterol with DPPC, DAPC in molar fraction of 10% and 20% the solutions of pure phospholipids as well as mixtures DPPC/BSA and DPPC/CHOL/BSA were spread at the air/water interface of a Teflon-made LB. Homogeneous molecular monolayers of DMPC,DPPC, DAPC, DMPE and DPPE phospholipids and DPPC/CHOL, DAPC/CHOL hybrid nanoscale were successfully produced and characterized surface pressure isotherms (area). The isotherms have indicated also the presence of the transitions of phases G, LE, LE/LC and LC. Modeling surface pressure (-A) isotherms for mixed monolayers with cholesterol were calculated using the additive rule. The interaction between the components in a mixed monolayer and the thermodynamic stability of a mixed monolayer compared with pure components were investigated from the evaluation of excess free energy of mixing. The surface adsorption of BSA in monolayers of DPPC and DPPC/CHOL wasevaluated by isotherms -A.