Nanomechanical Characterization of Phospholipid Bilayer Islands on Flat and Porous Substrates: A Force Spectroscopy Study

Abstract

In this study, we compare for the first time the nanomechanical properties of lipid bilayer islands on flat and porous surfaces. 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) bilayers were deposited on flat (silicon and mica) and porous silicon (pSi) substrate surfaces and examined using atomic force spectroscopy and force volume imaging. Force spectroscopy measurements revealed the effects of the underlying substrate and of the lipid phase on the nanomechanical properties of bilayers islands. For mica and silicon, significant differences in breakthrough force between the center and the edges of bilayer islands were observed for both phospolipids. These differences were more pronounced for DMPC than for DPPC, presumably due to melting effects at the edges of DMPC bilayers. In contrast, bilayer islands deposited on pSi yielded similar breakthrough forces in the central region and along the perimeter of the islands, and those values in turn were similar to those measured along the perimeter of bilayer islands deposited on the flat substrates. The study also demonstrates that pSi is suitable solid support for the formation of pore-spanning phospholipid bilayers with potential applications in transmembrane protein studies, drug delivery, and biosensing.

Polydopamine-Supported Lipid Bilayers

“…We also measured bilayer thicknesses of 3.5 ± 1.5 nm for DMPC and 4.0 ± 1.5 nm for DOPC. These values are comparable to other reported data for DMPC [35,36] and DOPC [37] bilayers formed on mica. In addition, RMS roughness values of ~1.3 nm for DMPC and ~1.7 nm for DOPC (area of 5 µm × 5 µm) were determined for the bilayers.…”

Nanoscale Measurement of the Dielectric Constant of Supported Lipid Bilayers in Aqueous Solutions with Electrostatic Force Microscopy

“…The images show that the DPPC lipid bilayer partially covers the Si þþ substrate and the SiO 2 stripes, with a total surface coverage of~20%. The measured lipid bilayer thickness was~5 nm, in good agreement with values reported in the literature for DPPC (27,28). We note the occasional presence of double bilayers and of small isolated bilayer patches with dimensions in the micrometer-to-hundred-nanometers range, more clearly observed in the phase image as small spots (Fig.…”

Aqueous-filled polymer microcavity arrays: versatile & stable lipid bilayer platforms offering high lateral mobility to incorporated membrane proteins

“…However, most such techniques function in restricted conditions such as the limited (nano-dimensioned) size of the pores and the vesicles 16,17 , application of sheer flow and pH 18 , the use of Giant Unilamellar Vesicles (GUVs) 14, or spanning over dry substrates, where stability is a significant issue. [20][21][22][23] While each of these methods have shed light on the mechanisms of a variety of pore-spanning lipid membranes, the incorporation and manipulation of membrane proteins within artificial systems remains a challenge. Herein, we describe a robust new supported lipid membrane model in which both lipid bilayer and reconstituted membrane proteins are highly mobile and evidently decoupled from the underlying substrate.…”