The Effects of Anaesthetics and Cholesterol on Tethered Lipid Bilayers

Cells are enveloped by a thin (4 nm) impermeable membrane which is mainly responsible for insulating the cell interior from the external environment. Due to the complexity of cell membranes, artificial lipid membranes models have emerged in order to study their physical, mechanical and electrical properties. The main challenge in the creation of these model membranes has been the creation of lipid membranes with enhanced stable properties that can withstand the external electric pulses and temperature changes. Tethered lipid membranes (tBLM) have emerged as providing a superior stable artificial lipid membrane that mimics biological membranes. In this study, (tBLM) were constructed on a commercially available chemically modified gold substrate. The Surgical Diagnostics SDx® tethered membrane chip was used to explore the effects of a local anaesthetic, benzyl alcohol (BZA), a general anaesthetic, xenon and cholesterol on the electrical properties of lipid membranes. Very high resolution electrical impedance spectroscopy (EIS) was used to determine the dielectric structure of the lipid bilayers. Voltage–current (V-I) measurements of the tBLM were also measured using triangular voltage ramps of 0–500 mV. In this thesis, the results of measurements of the temperature dependence of the conductance of tBLM with BZA, xenon and cholesterol, incorporated in their structures are presented. An evaluation of their activation energies allowed conclusions to be drawn. The results showed that BZA caused a significant increase in the capacitance (corresponding to a decrease in the bilayer thickness) of the hydrophobic region and an increase in the membrane’s electrical conductance. The general anaesthetic xenon was found to decrease membrane’s capacitance and electrical conductivity. The results also showed that cholesterol inhibited pore formation when present in low concentrations in the tBLM