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Biomimetic Membrane Properties and the Morphology of Giant Hybrid Vesicles with Phospholipid/block Copolymer Coexistence

Jin Nam1, Paul A. Beales1, and T. Kyle Vanderlick2. (1) Department of Chemical Engineering, Princeton University, Engineering Quadrangle, Princeton, NJ 08544, (2) Department of Chemical Engineering, Yale University, 10 Hillhouse Ave, Dunham Laboratory 236, New Haven, CT 08544

A number of elaborate liposome systems and theories based on fluid phospholipid membranes have been investigated and their synthetic analogue, amphiphilic diblock copolymers have provided an alternative to phospholipids as mimics of the cell membrane with the unique morphology and a variety of tunable properties. Though phospholipids can afford lots biological functionalities in the flexible membrane the application is limited due to the low stability in circulation. The biomimetic membrane system made of diblock copolymer can impart structural stability into lipid based vesicles bilayer architectures. Therefore, with each of the advantages of lipid membrane biofunctionalities and amphiphilic copolymers structural stability we create self-assembled giant hybrid lipid/diblock copolymer vesicles and study changes in the morphology and membrane mechanical properties of the hybrid vesicle membrane. The effect of lipid to copolymer ratios on the vesicle membrane is studied with a micropipette aspiration technique and the morphology is characterized by confocal microscope. Phospholipids formed micron sized multi-spot domains within a diblock copolymer matrix and the number of domains increased at higher lipid concentrations. We also study the possibility of pore formations from the spot domains generated by lipid extraction with surfactant seeking formation of multi-functional constructs whose bilayers are perforated or decorated with biofunctional molecules such as functional liposome carriers with biological windows. The unique vesicular morphology having pores is highly beneficial in biological applications not only in such fields as delivery-release but also micro-machinery vehicles with incorporation of biological materials.