Robust hybrid thin films that incorporate lamellar phospholipid bilayer assemblies and transmembrane proteins

This study describes facile methods based on sol-gel processing for the formation of robust thin films that incorporate phospholipid bilayer membranes and transmembrane proteins as multilamellar assemblies in cross-linked silica matrices. Transmission electron microscopy and x-ray diffraction were used to examine the lamellar structure of the hybrid thin films containing 1, 2-dioleyl-sn-glycero-3-phospoethanolamine (DOPE), an unsaturated lipid, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), a saturated lipid. While the d spacing measured for DOPE containing films varied (from 35 to 48 Å) depending on the amount of DOPE added to the coating solution (10-1 wt %), similar changes were not observed for the films containing saturated lipid, DMPC (d spacing ∼43 Å). Addition of purple membrane containing bacteriorhodopsin to the DOPE/silica coating solution led to the formation of multilamellar vesicle-like structures within the thin films. Mild sonication of these solutions containing the purple membrane prior to coating led to the formation thin films with planar multilamellar structures that exhibit uniform d spacing. The study further investigates the effects of incorporation of gramicidin and sonication on the structure of hybrid films and speculates on the eventual application of thin films prepared in this manner.