Effect of surface treatment on diffusion and domain formation in supported lipid bilayers

Abstract

Supported lipid bilayers are widely used as model systems due to their robustness. Due to the solid support, the properties of supported lipid bilayers are different from those of freestanding bilayers. In this article, we examine whether different surface treatments affect the properties of supported lipid bilayers. It will be shown that depending on the treatment method, the diffusion of the lipids can be adjusted approximately threefold without altering the composition. Additionally, as the bilayer-support interaction decreases, it becomes easier to form coexisting liquid-ordered and liquid-disordered domains. The physical/chemical alterations that result from the different treatment methods will be discussed.

FIGURE 1

Typical FRAP recovery data for a DOPC supported lipid bilayer containing 0.5 mol % NBD-PC with a least-squares fit to Eq. 1. Residuals for the fit to Eq. 1 are at the top of the graph.

FIGURE 2

Diffusion coefficients of DOPC supported lipid bilayers, containing 0.5 mol % NBD-PC on solid glass supports, plotted as a function of piranha-etched surface treatment time (open squares). Plotted at t = 0 are the diffusion coefficients of supported lipid bilayers on baked slides (open triangle) and on detergent-only slides (open circle).

FIGURE 3

Epifluorescence image of a supported lipid bilayer containing 2:1 DOPC/DPPC with 15 mol % cholesterol and 0.1 mol % TR-DHPE on a piranha-etched glass slide, after heating at 60°C for 1 h. The image is 35 μm × 35 μm and was acquired at room temperature.

FIGURE 4

X-ray photoelectron spectra of the Si(2p) region. Three treatment methods were examined: baked, 5-min etched, and 20-min etched.

FIGURE 5

AFM line scans and corresponding images of a baked slide and slides etched for 5, 20, 40, and 60 min. Note: the height scale has been emphasized to help visualize the small change in surface undulations.