New Process to Create Artificial Cell Membranes Developed

Understanding the myriad biochemical roles of membranes surrounding cells and inside them requires the ability to prepare realistic synthetic versions of these complex multilayered structures, a long-standing challenge. In a study published in the journal Nature Chemistry, online September 29, 2013, scientists at The Scripps Research Institute (TSRI; Jupiter, FL, USA) describe an innovative method they have developed for studying cell-like membrane-enclosed vesicles—layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity.

Starting with a technique commonly used to deposit molecules on a solid surface, Langmuir-Blodgett deposition, the scientists repurposed the approach to work on liquid objects. They engineered a microfluidic device containing an immobilized array of microscopic cups, each trapping a single droplet of water bathed in oil and lipids. The arrayed trapped droplets are then ready to serve as a foundation for building up a series of lipid layers like coats of paint. “Layer-by-layer membrane assembly allows us to create synthetic cells with membranes of arbitrary complexity at the molecular and supramolecular scale,” said TSRI Assistant Professor Brian Paegel, who authored the study with Research Associate Sandro Matosevic; “We can now control the molecular composition of the inner and outer layers of a bilayer membrane, and even assemble multilayered membranes that resemble the envelope of the cell nucleus.”

The lipid-coated water droplets are first bathed in water. As the water/oil interface encounters the trapped droplets, a second lipid layer coats the droplets and transforms them into unilamellar vesicles. Bathing the vesicles in oil/lipid deposits a third lipid layer, which is followed by deposition of a final layer of lipids. The final product after these three phase exchanges is an immobilized array of double-bilayer vesicles.

“The computer-controlled microfluidic circuits we have constructed will allow us to assemble synthetic cells not only from biologically derived lipids, but from any amphiphile and to measure important chemical and physical parameters, such as permeability and stability,” said Prof. Paegel.

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