We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.
Bibliographical noteFunding Information:
This work was supported in part by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2011-0028422). This work was also supported in part by grants from the Minnesota Partnership for Biotechnology and Medical Genomics (Y.S.R., N.J.W., S.H.O.) National Science Foundation (CAREER Award; Y.S.R., S.H.O.), MnDrive Research Initiative (N.J.W. and S.H.O.), Department of Energy (BES #DEFG02-04ER46173; A.N.P.). We acknowledge that molecular models used in Figure S4 (Supporting Information) were reproduced from the Avanti website (http://avantilipids.com).