Polymerizable surfactant design for transmission electron microscopy |
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| Authors: | Joseph A. N. Zasadzinski Paul C. Vosejpka Wilmer G. Miller |
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| Affiliation: | 1. Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 USA;2. Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 USA;1. Department of Pharmacy and BioTechnologsssy, PharmTech Lab, University of Bologna, Via S. Donato 19/2, 40127, Bologna, Italy;2. Department of Chemical and Pharmaceutical Sciences, University of Trieste, P.le Europa 1, 34127, Trieste, Italy;1. CSIR- Central Electrochemical Research Institute, Karaikudi, Tamil Nadu-630 003, India;2. Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India;1. State Key Laboratory for Advance Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China;2. Department of Mechanical Engineering, McGill University, Montreal, Québec, H2A0C3, Canada;3. Department of Mining and Materials Engineering, McGill University, Montreal, Québec, H3A0C5, Canada;1. Department of Engineering Mechanics, Tsinghua University, Beijing, China;2. Institute of Advanced Structure &Technology, Beijing Institute of Technology, Beijing 100081, China;3. State Key Laboratory for Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China;4. Faculty of Engineering, University of Porto (FEUP), R. Dr. Roberto Frias, 4200-465 Porto, Portugal;1. Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China;2. AMPTL, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;3. Aero-engine Thermal Environment and Structure Key Laboratory of Ministry of Industry and Information Technology, College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;4. Materials & Manufacturing Qualification Group, Corporate Technology, Siemens Ltd., China, Beijing 100102, China;5. State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;6. School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Polymerized liposomes and vesicles are under close scrutiny as long-lived, stable substitutes for their natural and synthetic unpolymerized counterparts. The monomer surfactant, which contains one or more polymerizable groups, is dispersed in water at the proper temperature and concentration to form the lyotropic liquid crystalline phase of interest and polymerized while in the liquid crystalline state. In addition to their applications to slow-release and site-specific drug delivery, membrane-mediated chemistry, artificial photosynthesis, etc., polymerized surfactant liposomes and vesicles hold great promise as model systems for TEM investigations of lamellar liquid crystal structure. One such model polymerizable surfactant is DBPAl, or N,N-dimethyl-N,N-bis(1,3-pentadecadienyl-carbonyloxyethyl) ammonium iodide. Polarized light microscopy and differential scanning calorimetry (DSC) confirm that DBPAI forms lamellar liquid crystalline liposomes in water. The DBPAI liposomes were polymerized while in the liquid crystalline state by ultraviolet (UV) irradiation. The DBPAI liposomes were shown to be identical in structure before and after polymerization by a combination of X-ray diffraction and freeze-fracture TEM. However, turbidity measurements showed that the polymerized DBPAI liposomes were much more stable in acetone and ethanol than the monomer DBPAI liposomes, demonstrating that the chemical nature of the surfactant in the liposome had changed. The combination of structural preservation and enhanced chemical stability makes DBPAI a natural choice for TEM thin-sections. A method of preparing DBPAI liposomes for thin-section TEM is outlined and bilayer resolution images of the DBPAI liposomes are presented. Polymerized bilayers in thin-section TEM promise the enhanced resolution required to answer many important structural questions left unresolved by freeze-fracture TEM. |
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