Biomembrane Fabrication by the Solvent-assisted Lipid Bilayer (SALB) Method

Abstract

In order to mimic cell membranes, the supported lipid bilayer (SLB) is an attractive platform which enables in vitro investigation of membranerelated processes while conferring biocompatibility and biofunctionality to solid substrates. The spontaneous adsorption and rupture of phospholipid vesicles is the most commonly used method to form SLBs. However, under physiological conditions, vesicle fusion (VF) is limited to only a subset of lipid compositions and solid supports. Here, we describe a one-step general procedure called the solvent-assisted lipid bilayer (SALB) formation method in order to form SLBs which does not require vesicles. The SALB method involves the deposition of lipid molecules onto a solid surface in the presence of water-miscible organic solvents (e.g., isopropanol) and subsequent solvent-exchange with aqueous buffer solution in order to trigger SLB formation. The continuous solvent exchange step enables application of the method in a flow-through configuration suitable for monitoring bilayer formation and subsequent alterations using a wide range of surface-sensitive biosensors. The SALB method can be used to fabricate SLBs on a wide range of hydrophilic solid surfaces, including those which are intractable to vesicle fusion. In addition, it enables fabrication of SLBs composed of lipid compositions which cannot be prepared using the vesicle fusion method. Herein, we compare results obtained with the SALB and conventional vesicle fusion methods on two illustrative hydrophilic surfaces, silicon dioxide and gold. To optimize the experimental conditions for preparation of high quality bilayers prepared via the SALB method, the effect of various parameters, including the type of organic solvent in the deposition step, the rate of solvent exchange, and the lipid concentration is discussed along with troubleshooting tips. Formation of supported membranes containing high fractions of cholesterol is also demonstrated with the SALB method, highlighting the technical capabilities of the SALB technique for a wide range of membrane configurations.

Thermodynamic Modeling of Solvent-Assisted Lipid Bilayer Formation Process

“…Micromachines 2022, 13, 134 2 of 9 A recently developed strategy, termed the solvent-assisted lipid bilayer (SALB) formation [24][25][26][27], offers a simple, robust, and highly efficient protocol to fabricate SLBs. The substrate that needs to be coated is placed in a microfluidic chamber that contains phospholipids in a water-miscible organic solvent.…”

“…The design of the flow channel and the setup of the microfluidic system have been introduced in our previous publication [24]. This one-step SLB fabrication route [26] represents a more simplified workflow than existing methods, and works for a wider range of phospholipids and sterol compositions [28,29]. Since it does not depend on the quality of lipid bilayers at the water-air interface, or on the controlled rupture of lipid vesicles, this method effectively overcomes the technical difficulties of existing methods.…”

Water Structure in the Submembrane Region of a Floating Lipid Bilayer: The Effect of an Ion Channel Formation and the Channel Blocker

“…Such behavior is characteristic of a response reported for SUVs spreading and formation of the planar bilayer. 37,38,39 Upon reaching critical concentration, the vesicles rupture and release water contained in their interiors. This process causes a decrease in the mass deposited on the gold surface and an increase in the rigidity of the adsorbed layer.…”

Tailoring a Solvent-Assisted Method for Solid-Supported Hybrid Lipid–Polymer Membranes

“… 38 − 40 Of particular interest is the SA method as it is straightforward and requires no special equipment or complex and time-consuming sample preparation conditions. 38 , 40 Briefly, the amphiphilic molecules are dissolved in an organic solvent, which is then continuously replaced by an aqueous phase, which triggers the self-assembly process and induces the membrane formation. While the SA method has been previously used to generate lipid membranes 39 , 41 and very recently polymer membranes, 42 its potential to develop hybrid membranes has not yet been explored.…”