Development of integrated model biological membranes on solid substrates

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Micropatterned phospholipid bilayers on solid substrates offer an attractive platform for various applications, such as high throughput drug screening. We are currently developing a method for generating micropatterned bilayers composed of polymerized and fluid lipid bilayers. Lithographic photopolymerization of a diacetylene-containing phospholipid (DiynePC) allowed facile fabrication of compartmentalized arrays of fluid lipid membranes. In the present project, we could find a key experimental parameter, that significantly influenced the homogeneity and quality of the fabricated polymeric bilayers, namely the temperature at which monolayers of monomeric DiynePC were formed on the water surface and transferred onto solid substrates by the Langmuir-Blodgett/Langmuir-Schaefer (LB/LS) technique. Using the fluorescence microscopy and atomic force microscopy, it was found that polymerized bilayers were homogeneous, if bilayers of DiynePC were prepared below the triple point temperature (ca. 20℃) of the monolayer, where a direct transition from the gaseous state to the liquid condensed state occurred. The differences were attributed to the domain structures in the monolayer that was transferred from the water surface to the substrate. Another important result from the project is the development of a method to incorporate lipid membranes with membrane proteins. We used mixtures of short and long chain phospholipid, 1, 2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). We demonstrated that formation of planar bilayers was significantly accelerated in the presence of DHPC. Furthermore, membranes containing calcium channels(SR membranes from rabbit muscle) could be incorporated in the model membrane. These results suggest that the use of the mixtures of short and long chain phospholipids could be a convenient means for preparing integrated model membranes.