Muscovite (Mica) Allows the Characterisation of Supported Bilayers by Ellipsometry and Confocal Fluorescence Correlation Spectroscopy

Abstract

We demonstrate for the first time that ellipsometry and confocal fluorescence correlation spectroscopy (FCS) are complementary methods for the characterisation of supported planar phospholipid bilayers (SPBs) formed on mica, a mineral used in atomic force microscopy investigations of SPBs. Addition of small unilamellar vesicles containing 20% dioleoyl-phosphatidylserine (DOPS) and 80% dioleoyl-phosphatidylcholine (DOPC) to an oxidised borosilicate surface, on the other hand, results in a planar lipid system characterised by lateral diffusion coefficients which are three time smaller than those obtained for SPBs. Moreover, seven labelled phospholipids were tested for their suitability in the FCS characterisation of vesicles as well as of SPBs.

Recent Developments in Fluorescence Correlation Spectroscopy for Diffusion Measurements in Planar Lipid Membranes

“…SLBs are, on the other hand, a considerably less realistic model system, but very easy to prepare and stable and, thanks to their very well-defined geometry, accessible to characterisation by a wide range of experimental techniques [58,174–176]. They are formed on hydrophilic surfaces such as mica, glass, fused silica [51,175] or self-assembled alkanethiol monolayers [177,178] via adsorption and fusion of lipid vesicles [175,179,180] or via Langmuir–Blodgett and Langmuir–Schaefer techniques [59,181,182]. Although the lipid bilayer is separated from the solid surface by a thin aqueous layer (in the order of nm), thanks to which the bilayer retains its fluidity [183–185], the proximity of the support has a significant influence on the properties of the lipid membrane.…”

“…Simplified artificial models of biological membranes are, therefore, widely used in order to establish a deeper understanding of the influence which membrane composition and structure have on the lateral mobility of its constituents. Among such model systems, planar lipid membranes are widely used, because they can be characterized by a wide range of experimental techniques and are very convenient for lateral diffusion investigations [51–53]. Planar lipid membranes may be divided into two main groups: free standing membranes, such as giant unilamellar vesicles (GUVs) [54–56], and membranes on solid supports, such as supported lipid bilayers (SLBs) [57–59].…”

Insights into the pathophysiology of the antiphospholipid syndrome provided by atomic force microscopy

“…Benes and colleagues (2002; 2004) validated the use of muscovite mica with miniscule surface roughness as a base platform that would provide reproducible planar flatness for nanoscale AFM imaging.…”

Development of Biomimetic Surfaces by Vesicle Fusion

“…Important theoretical (Lipowsky, R. and Seifert, U., 1991;Seifert, U., 1997) and experimental (Benes, M., Billy, D., Hermens, W. T., and Hof, M., 2002;Csucs, G. and Ramsden, J. J., 1998;Egawa, H. and Furusawa, K., 1999;Hubbard, J. B., Silin, V., and Plant, A. L., 1998;Johnson, J. M., Ha, T., Chu, S., and Boxer, S. G., 2002;Keller, C. A. and Kasemo, B., 1998; A., Glasmastar, K., Zhdanov, V. P., and Kasemo, B., 2000; Koenig, B. W., Gawrisch, K., Krueger, S., Orts, W., Majkrzak, C. F., Berk, N., and Silverton, J. V., 1996; Lingler, S., Rubinstein, I., Knoll, W., and Offenhausser, A., 1997; Reimhult, E., Hook, F., and Kasemo, B., 2003;Reviakine, I. and Brisson, A., 2000; Williams, L. M., Evans, S. D., Flynn, T. M., Marsh, A., Knowles, P. F., Bushby, R. J., and Boden, N., 1997) work has been conducted in an effort to understand this useful process.…”

“…Other techniques that have been used to detect the formation of SPBs by this process are neutron reflectivity (Koenig, B. W., Gawrisch, K., Krueger, S., Orts, W., Majkrzak, C. F., Berk, N., and Silverton, J. V., 1996), atomic force microscopy (Egawa, H. and Furusawa, K., 1999;Reviakine, I. and Brisson, A., 2000), confocal fluorescence correlation spectroscopy and nulling ellipsometry (Benes, M., Billy, D., Hermens, W. T., and Hof, M., 2002). In these studies, rarely have there been any attempts to look at the kinetics of the process while making an effort to interpret the results in terms of mass transport models (Csucs, G. and Ramsden, J. J., 1998;Hubbard, J.…”