Biomimetic Membrane Approach

Abstract

Biomimetic membrane approach is based on artificial membranes which imitate fundamental properties and functions of biological mem-branes. Biomimetics develops simple and effi-cient synthetic systems that mimic the formation, structure, or function of biological materials, leading to new, more efficient, and cheap applications. Major potential applications of biomimetic membranes are drug delivery, high-throughput screening, sensors, and separa-tion and purification, possibly coupled with chemical synthesis (Hélix-Nielsen 2012). The same membrane can serve an opposite purpose and be used as an experimental model of biomembranes. The term biofunctional mem-brane is more appropriate for the membranes, which include biological components, such as specific enzymes, aquaporin, antigens, etc. Biological membranes have a lot of different specific functions but all of them separate either two aqueous phases or an external gaseous and internal aqueous phase. Three major chemical components of biological membrane are proteins, lipids, and polysaccharides, and selective perme-ability is based on direct diffusion, facilitated transport with carriers, and penetration through the channels. Coupling with various energy sources, including light, adenosine triphosphate, and different ion concentrations separated by the membrane aqueous solutions, leads to the trans-membrane active transport. Membrane processes can be controlled by temperature, transmembrane voltage, biochemical mediators, and drugs. Amphiphilic molecules are usually able to spontaneously form liquid crystal structures. These self-assembled structures, especially lipid monolayers, multilamellar vesicles, unilamellar liposomes, and bilayer lipid membranes can be used as models of biomembranes. To improve their stability, which is important for practical applications, lipid membranes are often immobilized on a solid support, which may be metal, glass, semiconductors, and polymers. The well-known example is Langmuir-Blodgett films. Lipids or their analogs may have an additional anchor group for tethering to a support. Sulfhy-dryl or disulfide groups are often used for tether-ing to the metals such as gold or silver, while methyl-and methoxy-substituted silane groups – for tethering to glass, quartz, silica, and mica. Micro-and nano-porous solid supports, including hydrophobic membrane filters, are also used to stabilize thin and nonstable bilayer lipid membranes. Though the thickness of lipid membranes (~50 Å) and some other structural properties are similar to the characteristics of biological mem-branes, electrical conductivity and permeability for inorganic ions are often four orders of # Springer-Verlag Berlin Heidelberg 2014