Lipid Bilayer Membranes: Production and Biophysical Characterization

Bilayer lipid membranes mimic the lipid portion of any cell membrane, therefore they are largely used for studying transmembrane transport, reconstitution of membrane channels and receptors, and binding of molecules and other small ligands. Two important physical features of an artificial lipid membrane must be monitored to assess its integrity and correct biological functionality: unilamellarity, to assure that only a bilayer is formed, and conductance, to assure negligible leakage. This work describes the production and physical characterization of bilayer lipid membranes. To physically describe the membrane, we assumed an equivalent electrical circuit consisting of a parallel plate capacitor and a resistor. After membrane formation, we determined its unilamellarity from its thickness, which was indirectly estimated from capacitance measurements. This was done by measuring the rectangular capacitive current measured in response to a triangle voltage for which dV/dt = ±1. The membrane’s conductance was determined by measuring the ionic currents in response to step voltages. Our investigations indicate production of a bilayer membrane with a negligible leakage. In conclusion, electrical methods are powerful approaches for establishing if artificial membranes replicate the lipid partition of a real cell membrane.