Formation and Characterization of Planar Phospholipid Bilayers Supported on TiO2 and SrTiO3 Single Crystals

Supported phospholipid bilayers have been prepared on rutile TiO 2 and SrTiO 3 single-crystal substrates. Fluidlike bilayers were successfully deposited onto each surface by Langmuir−Blodgett and Langmuir−Schaeffer methods and the vesicle adsorption and fusion method. The characteristics of membranes supported on TiO 2 and SrTiO 3 single crystals were evaluated using fluorescence pattern photobleaching recovery, fluorescence imaging, and differential interference contrast imaging, and the results were compared to similar preparations on fused silica. Diffusion coefficients of a fluorescent lipid in membranes supported on all substrates were on the order of 10 - 8 cm 2 /s, and fractional mobilities were 74−99%. Measured diffusion coefficients were faster for fluorescent lipids in bilayers on TiO 2 and SrTiO 3 than in bilayers on fused silica, and some sample types exhibited two diffusing species rather than a single diffusing species. Both the intensities and bleachabilities of the fluorescent lipids were significantly reduced for bilayers on TiO 2 and SrTiO 3 as compared to fused silica. A new theoretical model for interpreting fluorescence pattern photobleaching recovery data for fluorescent lipid diffusion in planar membranes is described. The ability to form planar phospholipid bilayers on TiO 2 and SrTiO 3 is expected to facilitate new developments in total internal reflection fluorescence microscopy, surface-based assays of importance in biotechnology, and biosensors.