Formation Of Mimetic Biomembrane Arrays Far Away From The Substrate

Cells are the basic unit of lives. Biomembranes consist of cell membranes andintracellular membranes. Both of them contain phopholipid bilayer as a skeleton ofbiomembranes. Membrane proteins are embedded in lipid bilayers. Membrane proteinsare responsible for the function of membranes. Most of them are involved in theexchange of substance directly. It is estimated that about50%of drugs in the markettarget membrane proteins. Hence, the structural analysis of membrane proteins isbecoming more and more significant. It is a very hot issue currently. Recently, artificiallipid membranes are used to study the structure, property and functions ofbiomembranes, which can be formed by spontaneous fusion of lipid vesicles ontohydrophilic surface such as silica surface. Generally the distance between the substrateand the phospholipid membrane is about1nm, which causes a difficulty to reconstitutetransmembrane proteins. Hence, it is necessary to build lipid bilayers far away from thesubstrate, so that it is suitable for reconstitution of transmembrane proteins. This newtype of model membrane is also more similar to real biomembranes due to the minorinfluence from the substrate.In this paper, we use ITO electrodes as substrates to form the biomimeticmembrane arrays standing far away from substrates. The main content consists of twoparts: first, formation of APTES self-assembled membranes on ITO electrode anddetermination of its surface pKa; second, formation of microwell arrays bylayer-by-layer technology according to the surface pKa. Details are as follows:1. The ITO electrode with APTES self-assemble membranes was fabricated. Theterminal groups of the membranes are amino groups, which can exist in two states in thesolution, i.e. protonated and deprotonated states. Two convenient and cost-effectivemethods, cyclic voltammetry and electrochemical impedance spectroscopy, were usedto determine the pKa of APTES monolayer on ITO electrode, which to be near5.6.2. The biomimetic membrane array was formed on the microwell arrays fabricatedby the alternate deposition of polyelectrolyte PSS and PDDA on the electrode.Polyelectrolyte PSS and PDDA were applied to thicken the thickness of the microwellarrays. Deep ultraviolet irradiation was used to pattern the surface. The electrode withpatterned structure was immersed into the phospholipid vesicles solution for a certainperiod of time. The vesicles will rupture and spread on the microwell arrays to formlipid bilayer arrays far away from the substrate.