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Preparation And Characterization Of Solid-Supported Biomimetic Membranes

Posted on:2011-05-17Degree:MasterType:Thesis
Country:ChinaCandidate:M WuFull Text:PDF
GTID:2210330338973416Subject:Biochemical Engineering
Abstract/Summary:PDF Full Text Request
Solid-supported membrane is one of the artificial membrane model systems.The presence of supporting medium makes the membranes more stable, which could sustain for days, and makes it possible to prepare cm2-scale membrane. It enhances the membranes'mechanical strength while keeping the fluidity of the membrane. Solid-supported membrane can be applied in many fields, especially biological, and medical technologies, such as the mobility of lipid molecular, structure of membrane, integration of proteins in lipid membrane, biosensors, new drug screening, etc.Amphiphilic block copolymer can self-assemble into ordered nanometric membrane in selective solvent. With regard to lipid molecular, this copolymer is more stable in chemical and mechanical properties, moreover, the composition, length and structure of the block could be regulated and desined precisely, so that this copolymer will have a good diversity. Furthermore the solid supported polymer-based will spread the research scope of biological membrane. It is known that porous silicon displays Fabry-Perot interference fringes when it is illuminated with white light, whose peak is correspond to the thickness and the refractive index of the porous layer. Thus the membrane supported on porous silicon could be expected to be a new kind of biosensor with the aide of its special optical reflectivity spectrum.The aim of this thesis is to prepare several kinds of solid-supported membranes using different support media and membrane materials, and further application on the research on membrane and membrane proteins can be expected with this technology.The cationic ring-open polymerization of 2-methyloxazoline initiated by PDMS thiosulfonate was carried out. And ABA amphiphilic block copolymer of PMOXA24-PDMS74-PMOXA24 with a molecular weight of 9680g/mol was synthesized. Its polydispersity was 1.6 with the determination by GPC. The synthesis of this copolymer was testifed by 1H-NMR and FTIR.The DOPC liposomes with a mean diameter of 154.1 nm and a polydispersity of 0.13 were prepared by extrusion, and the supported bilayers lipid membranes were formed on highly hydrophilic silicon and mica surfances with the liposome solution by fusion method. The formation of the membrane was confirmed by AFM and its thickness was about 3.74 nm measured by ecllipsometry. Likewise, copolymer vesicles with a mean diameter of 46.7 nm measured by number and a polydispersity of 0.23 was prepared. Copolymer membranes supported on mica and silion were prepared by deposition of vesicles. The contact angle of each increased to 40.9°and 45.2°from 3.0°and 37.1°respectively, and the thickness of the membrane was about 6.64 nm measured by ecllipsometry, which confirmed the formoation of membranes. Furthermore, a copolymer membrane with a thickness of 3.57 nm was prepared by LB method.The porous silicon with typical pore size of 35-50 nm in diameter and 15 u m in depth was prepared by electrochemical etching. Its surface's contact angle was 15.9°after oxidation under air at 450℃for 2h. Atomic force microscopy (AFM) measurements were carried out to observer the morphology of the sample surface and the results showed that the Root Mean Squared Roughness(RMS) was only 0.643nm. The bilayers lipid membrane supported on porous silicon was formed by deposition of the liposome solution. The AFM measurements showed that the lipid bilayer membrane formed on the porous silicon's surface and the thickness of the membrane was about 3.87 nm. Furthermore, the formation of the membrane was confirmed by testing the ability of the porous silicon supported membrane to exclude the ions based on the reflective interference of porous silicon.
Keywords/Search Tags:Solid-supported membrane, liposome, amphiphilic three block copolymer, porous silicon, reflective interference, ellipsometry, AFM
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