Microfluidic Fabrication of Suspended Bilayers: Vertical and Horizontal
Experimental setups to produce and to monitor model membranes have been successfully used for decades and have brought invaluable insights into many areas of biology. However, they all have limitations that prevent the full-scale in vitro mimicking and monitoring of most biological processes. We developed two techniques that enable the production of a suspended physiological bilayer in a microfluidic chip: one that produces a vertical bilayer and a second that produces a horizontal bilayer. This bilayer-chip can be simultaneously integrated into a confocal microscope and a path-clamp amplifier. It is composed of poly(dimethylsiloxane) and consists of a 100 µm hole, where the horizontal (or vertical) planar bilayer is formed, connecting two open crossed-channels, which allows for altering of each lipid monolayer separately. The bilayer, formed by the zipping of two lipid leaflets, is free-standing, horizontal, stable, fluid, solvent-free, and flat with the 14 types of physiologically relevant lipids, and the bilayer formation process is highly reproducible. This bilayer is the central model system that we use to explore a wide range of biophysical phenomena (see publications).
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Depending on the project goal, the used device has to be adjusted and changed drastically.
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Vertical Bilayer Formation:
​Simultaneous measurement of surface and bilayer tension in a microfluidic chip Biomicrofluidics DOI: 10.1063/1.5137810
Horizontal Bilayer Formation:
Highly Reproducible Physiological Asymmetric Membrane with Freely-Diffusing Embedded Proteins in a 3D-Printed Microfluidic Setup Small DOI: 10.1002/smll.201900725
Microfluidic Fabrication of a Suspended Monolayer (as synthetic Lipid Droplet)
Lipid droplets (LD) are suborganelles localized in the membrane of the endoplasmic reticulum (ER) that play an important role in metabolic functions. They consist of a core of neutral lipids surrounded by a monolayer of phospholipids and proteins resembling an oil-in-water emulsion droplet. Many studies have been focused on the biophysical properties of these LDs. However, despite numerous efforts, we are lacking information on the mobility of phospholipids on the surface of LDs, although they may play a key role in protein distribution. In this article, we developed a microfluidic setup that allows the formation of a triolein-buffer interface decorated with a phospholipid monolayer. Using this setup, we measured the motility of phospholipid molecules by performing Fluorescent Recovery After Photobleaching (FRAP) experiments for different lipidic compositions. The results of the FRAP measurements reveal that the motility of phospholipids is controlled by the monolayer packing decorating the interface.
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Phospholipids Diffusion on the Surface of Model Lipid Droplets BBA - Biomembranes DOI: 10.1016/j.bbamem.2022.184074
