Simultaneous measurement of surface and bilayer tension in a microfluidic chip

Abstract

Freestanding lipid bilayers are one of the most used model systems to mimic biological cell membranes. To form an unsupported bilayer, we employ two aqueous fingers in a microfluidic chip surrounded by an oily phase that contains lipids. Upon pushing two aqueous fingers forward, their interface becomes decorated with a lipid monolayer and eventually zip to form a bilayer when the monolayers have nanoscopic contact with each other. Using this straightforward approach, the quick and easy bilayer formation is facilitated by oil draining into the microfluidic device material consisting of polydimethylsiloxane. However, the oil drainage limits the lifetime of a bilayer to about 1 h. We demonstrate that this drainage can be managed, resulting in superior bilayer stability and an increased lifetime of several hours when using a pressure-controlled system. Applying different pressures to the aqueous fingers in the microfluidic chip, the formed bilayer can even be bent to a desired curvature. Extracting the contact angle and the resulting curvature of the bilayer region, for a given applied pressure difference, both the bilayer tension and the surface tension of each lipid monolayer can be derived from a single experiment using the Young Laplace pressure equation.

Cholesterol promotes both head group visibility and clustering of PI(4,5)P2driving unconventional secretion of Fibroblast Growth Factor 2

“…To form a freestanding lipid membrane two microfluidic cross channel geometries previously tested as a platform to produce stable bilayers were employed (86)(87)(88). In both geometries, a continuous phase consisting of lipids dissolved in squalene solution (5 mg/mL) separates two fingers of HEPES buffer (25 mM, KCl 150 mM).…”

Transport Properties of Gramicidin A Ion Channel in a Free-Standing Lipid Bilayer Filled With Oil Inclusions

“…Once the two aqueous fingers appear close to the gap of the x-junction, we lower the height of both plastic syringes to slow down their advancement. When both aqueous fingers reached the gap region, they touch each other and shortly after form a lipid bilayer membrane (Figure 1; Vargas et al, 2014;Khangholi et al, 2020). The two monolayers were brought in contact by microfluidic manipulation and touch each other but did not yet form a lipid bilayer.…”

“…Such planar lipid bilayer is consisting of two separated lipid monolayers stabilized by a solvent is referred to as a Black Lipid Membrane (BLM) (Oiki, 2012). Advantages of the BLM methods over lipid vesicles are the possibility of electrophysiological measurements and the exchange of chemical reagents without the need of tedious vesicle handling and manipulation (Montal and Mueller, 1972;Oiki, 2012;Khangholi et al, 2020). One of the recent approaches with this technique, the droplet interface bilayer (DIB), has been specifically developed to produce a solvent-free lipid bilayer having a rich lipid composition (Bayley et al, 2008).…”

“…Thus, many miniaturized apparatuses have been developed, such as microfluidic devices, to overcome the drawbacks of all the previous techniques (Funakoshi et al, 2006). Moreover, the formation of lipid bilayers in microfluidic devices presents the advantage of changing the buffer around the bilayer while enabling good optical and electrophysiological access without using an undesired solvent (typically oil), which is essential for various biotechnological purposes (Heo et al, 2019;Khangholi et al, 2020). However, the properties of these pores in heterogeneous membrane are not known (Cross et al, 1999;Kourie et al, 2002;Acharya et al, 2013).…”

Photoactivation of Cell-Free Expressed Archaerhodopsin-3 in a Model Cell Membrane

“…In this work, we present a new and simple microfluidic approach [ 24 ] to study the conducting properties of ion channels. We incorporated recombinantly produced Arch-3-EGFP into a free-standing lipid bilayer that mimics a biological membrane.…”