Supported phospholipid membranes as biometric labs-on-a-chip: analytical devices that mimic cell membrane architectures and provide insight into the mechanism of biopreservation

摘要

This dissertation focuses on the applications of solid supported phospholipidmembranes as mimics of the cellular membrane using lab-on-a-chip devices in order tostudy biochemical events such as ligand-receptor binding and the chemical mechanismfor the preservation of the biomembrane. Supported lipid bilayers (SLBs) mimic thenative membrane by presenting the important property of two-dimensional lateralfluidity of the individual lipid molecules within the membrane. This is the sameproperty that allows for the reorganization of native membrane components andfacilitates multivalent ligand-receptor interactions akin to immune response, cellsignaling, pathogen attack and other biochemical processes.The study is divided into two main facets. The first deals with developing anovel lipopolymer supported membrane biochip consisting of Poly(ethylene glycol)(PEG)-lipopolymer incorporated membranes. The formation and characterization of thelipopolymer membranes was investigated in terms of the polymer size, concentrationand molecular conformation. The lateral diffusion of the PEG-bilayers was similar tothe control bilayers. The air-stability conferred to SLBs was determined to be more effective when the PEG polymer was at, or above, the onset of the mushroom-to-brushtransition. The system is able to function even after dehydration for 24 hours. Ligandreceptorbinding was analyzed as a function of PEG density. The PEG-lipopolymer actsas a size exclusion barrier for protein analytes in which the binding of streptavidin wasunaffected whereas the binding of the much larger IgG and IgM were either partially orcompletely inhibited in the presence of PEG.The second area of this study presents a molecular mechanism for in vivobiopreservation by employing solid supported membranes as a model system. Themolecular mechanism of how a variety of organisms are preserved during stresses suchas anhydrobiosis or cryogenic conditions was investigated. We investigated theinteraction of two disaccharides, trehalose and maltose with the SLBs. Trehalose wasfound to be the most effective in preserving the membrane, whereas maltose exhibitedlimited protection. Trehalose lowers the lipid phase transition temperature andspectroscopic evidence shows the intercalation of trehalose within the membraneprovides the chemical and morphological stability under a stress environment.