Mechanical and electrical properties of biomimetic membranes in the presence of sweeteners

Abstract

Understanding the basic mechanisms driving cell division, neuron growth, endocytosis, or shape changes in organelles such as the endoplasmic reticulum requires a detailed knowledge on the membrane elastic properties. Revealing the governing principles involved in other processes like signaling and nerve pulse propagation necessitates the detailed characterization of the electrical properties of membranes. With their simple reproducibility in laboratory conditions at controlled membrane composition and physicochemical parameters of the surrounding aqueous medium, lipid bilayers represent a basic physical model of biomembranes successfully applied for determination of their physical properties. Giant unilamellar lipid vesicles are widely used in biophysical research as a powerful biomimetic tool for characterization of lipid membranes. We measure the bending rigidity and capacitance of lipid bilayers in aqueous solutions of aspartame and sorbitol, which are non-saccharide sweeteners with wide application in the food industry. Our interest in these compounds is motivated by the existing issues on their influence on the human organism raising questions about the impact of these molecules at membrane level. We employ deformation of lipid vesicles in AC fields to obtain the electrical capacitance of palmitoyl-oleoyl phosphatidylcholine bilayers in sorbitol solutions. Analysis of the thermal shape fluctuation of lipid vesicles is applied to determine the bending elasticity modulus of POPC membranes in the presence of aspartame or sorbitol in the aqueous solution. Their influence on the studied membrane properties is found to be different from the effect of sugars reported earlier.