Immobilization of artificial lipid membranes on one dimensional nanostructures and the detection of protein-mediated transport

This project attempts develop a protocol to synthesize negatively charged giant liposome for the purpose of immobilization onto nanostructures, such as Silicon Nanowires (SiNW) and Carbon Nanotubes (CNT). It is shown that, 2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC), Phosphatidylserine (PS) and cholesterol (9:1:3) can be used to form giant unilamellar vesicles (GUVs) that can successfully fuse to form a continuous and fluid lipid bilayer. An internal medium of 0.1M glucose and 10mM KCl was found to allow the swelling of the liposomes. Several modifications on the surfaces of these nano-devices are carried out to enhance the adsorption of the liposomes onto their surfaces in an attempt to create a model membrane. Florescence imaging, and quantitative electrical measurements such a front-gate or impedance measurements showed that modification of the SiNW with aminopropyltriethoxysilane (APTES) and modification of CNTs with Polylysine (PLL) enhanced the formation of the lipid bilayer onto their surfaces. These nanostructures were used as Field Electric Transistor (FET)-based sensors to detect the ability of an ionophore, Calcimycin to specifically transported calcium ions (Ca2+) across the membrane. It is shown that the ionophore is able to incorporate itself into the membrane and transport Ca2+ across the membrane, producing a significant change in the electrical signal. The ionophore was also sensitive to different concentration of Ca2+. Control experiments concluded that Calcimycin was not sensitive to other monovalent ions such as potassium (K+) or sodium (Na+). There was no effect on the model membrane upon the addition of other proteins such as Bovine Serum Albumin (BSA) and Adenosine Triphosphate (ATP). iii The advantage of this model is that it is able to detect the incorporation of the ionophore as well as the ions and thus serves as a good model for investigations of membrane associated proteins. It can even block interferences, such as other non-specific ions. This FET-based sensors can be used to enhance our understand other components of the biological membranes as well as other toxins using model membranes such as the one created in this project. The ability of this membrane model to electrically detect calcium ions using Calcimycin can be further developed into a calcium-based sensor. Further studies investigating the thermodynamics and kinetics of the incorporation of the ionophores such as Calcimycin can be carried out.Bachelor of Engineering (Chemical and Biomolecular Engineering