Electroformation of Giant Phospholipid Vesicles on a Silicon Substrate:  Advantages of Controllable Surface Properties

Abstract

We introduce the use of silicon (Si) as a substrate for the electroformation of giant phospholipid vesicles. By taking advantage of the tunability of silicon surface properties, we varied the organization of the phospholipid film on the electrode and studied the consequences on vesicle formation. In particular, we investigated the effects of Si surface chemistry and microtopology on the organization of the phospholipid film and the properties of the final vesicles. We established correlations between chemical homogeneity, film defects, and resulting vesicle size distribution. By considering phospholipid films that are artificially fragmented by electrode microstructures, we showed that the characteristic size of vesicles decreases with a decrease in microstructure dimensions. We finally proposed a way to control the vesicle size distribution by using a micropatterned silicon dioxide layer on a Si substrate.

Comparison of Actin- and Glass-Supported Phospholipid Bilayer Diffusion Coefficients

“…It is noted that the change of the diffusion mode occurred at approximately the main-phase transition temperature determined from the diffusion coefficients measured via z-scan FCS. Examination of the data for the glass-supported bilayers suggests similar results, with the change in the diffusion mode potentially occurring near the measured main-phase transition temperature of 24.3 C. However, the uncertainty of the data in the temperature range of [20][21][22][23][24] C prohibits any absolute statements about the diffusion behavior. Regardless, it is clear that there is a substrate-dependent difference in behavior in the [20][21][22][23][24] C temperature range when comparing the actin-supported and glass-supported bilayers.…”

“…The diffusion coefficients for the glass-supported membranes (Fig. 3, triangles) also increased with temperature, but over a more narrow range (22)(23)(24)(25)(26)(27)(28)(29)(30) C). The main-phase transition temperature for each model membrane was determined via …”

“…Clearly, to optimize the biological relevance of supported planar membrane systems, the choice of the supporting surface and the sample environment are critical. Further, detailed knowledge of substrate effects on lipid bilayer dynamics is essential for interpretation of lipid membrane behavior (2,22,23). As noted by Seeger et al (24), the inner leaflet of the membrane comes into direct contact with the supporting substrate, therefore the perturbation of the planar membrane system by the supporting substrate must be fully characterized.…”

Long-wave dynamics of an inextensible planar membrane in an electric field

“…In electroformation where an AC field is used (Angelava & Dimitrov 1987;Constantin et al 2005;Lecuyer et al 2006;Le Berre et al 2008), the AC field frequency is several Hz, the AC strength E 0 is often a few kilovolts per metre, σ 1 ∼ 10 −4 S m −1 , the channel height is in the range 100 µm h 0 1 mm and the channel aspect ratio usually satisfies 0.3 for a vesicle filling the channel ( = 2r 0 /2πr 0 = 1/π ∼ 0.3). In our non-dimensionalization, this gives a time scale h 0 C m /σ 1 ∼ 10 −1 s. Thus the maximum growth rate from figure 3(b,c) (for a tensionless planar membrane in an AC field) gives an estimate of several seconds for significant membrane deformation due to linear instability, consistent with results in Seiwert & Vlahovska (2013).…”

Novel Method for Synthesizing Monodisperse Dispersion of Nanometer Liposomes

“…Confinement inside small channels in an environment that provides controlled mixing enables synthesis of liposomes in the submicron range. Thus, adapting the conventional macroscale processes such as electroformation [15], hydration [16], extrusion [5], and double emulsion technique [26] to microfluidic devices prevents the loss of reagents while achieving a tight control on the liposome size. Recent microfluidic approaches by Jahn et al [12] and modification of the same using membranes by Akamatsu et al [1] have enabled the synthesis of monodisperse liposomes in the submicron range.…”