Engineering Biological Functions in Synthetic Systems

Lipid bilayers supported on porous or solid silica present a useful construct for the study of synthetic membrane systems as well as a potential platform for harnessing membrane bound proteins for diagnostic and bio-sensing purposes. In many cases, such as large-scale parallel studies, lateral organization of supported lipid bilayer components is desirable. Here, I present two unique cases of induced lateral lipid heterogeneity. The conditions for fusion and exchange of bilayer components between two independent supported bilayers are explored. A simple modulation of ionic strength is shown to control this transfer of lipids between a colloidal supported bilayer and a planar supported bilayer. This technique is then shown to be a viable method for making controlled modifications to the composition of individual elements in a supported bilayer array. Patterned deposition of mesoporous silica on non-porous glass results in a surface with alternating regions of raised, porous glass, and flat, non-porous glass. Lipid bilayers supported on such surfaces show small but meaningful differences in phase transition temperature in each region. These small differences are magnified greatly in phase separating mixtures and significant lateral segregation of components may be observed. This platform provides a means for measuring the effect of specific silica surface preparations on supported bilayer phase behavior. This is of vital importance in the design of membrane coated silica nano-particles for drug-delivery.;vii Chemically functionalized porous supports allow for optical reporting of trans-membrane proton transport. Specifically, a pH sensitive fluorescent dye embedded in the porous substrate reports on the concentration of protons underneath the lipid bilayer. This construct relies on side by side transporter regions composed of porous silica and reporter regions composed of FITC doped surfactant-templated meso-structured silica.