Formation and characterization of planar phospholipid bilayers supported on TiO2 and SrTiO3 single crystals

Supported phospholipid bilayers have been prepared on rutile TiO2 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 TiO2 and SrTiO3 single crystals were evaluated using fluoresce nce pattern photobleaching recovery, fluorescence imaging, and differential interference contrast imaging, and the results were compared to similar pr eparations on fused silica. Diffusion coefficients of a fluorescent lipid i n membranes supported on all substrates;were on the order of 10(-8) cm(2)/s , and fractional mobilities were 74-99%: Measured diffusion coefficients we re faster for fluorescent lipids in bilayers on TiO2 and SrTiO3 than in bil ayers on fused silica, and some sample types exhibited two diffusing specie s rather than a single diffusing species. Both the intensities and bleachab ilities of the fluorescent lipids were significantly reduced for bilayers o n TiO2 and SrTiO3 as compared to fused silica. A new theoretical model for interpreting fluorescence pattern photobleaching recovery data for fluoresc ent lipid diffusion in planar membranes is described. The ability to form p lanar phospholipid bilayers on TiO2 and SrTiO3 is expected to facilitate ne w developments in total internal reflection fluorescence microscopy, surfac e-based assays of importance in biotechnology, and biosensors.