Scientists from the Florida campus of The Scripps Research Institute have built a so-called microscopic assembly line designed to create the complex membrane structures of biological cells from simple chemical starting materials. They used the assembly line to create a laboratory version of the phospholipid bilayer surrounding all cells, organelles, and vesicles by mass producing synthetic cell-like compartments.
Details of the study are reported in the paper "Stepwise Synthesis of Giant Unilamellar Vesicles on a Microfluidic Assembly Line" published February 10 in the Journal of the American Chemical Society.
“We are constructing these synthetic systems to understand why compartmentalized chemistry is a hallmark of life and how it might be leveraged in therapeutic delivery,” says Brian Paegel, Scripps Research assistant professor and the study’s lead author.
The computer-controlled system transforms cell membrane synthesis into a controlled process customizable over a range of cell sizes and highly efficient in terms of cargo encapsulation, according to the Scripps team.
A microfluidic circuit generates water droplets in lipid-containing oil. The lipid-coated droplets travel down one branch of a Y-shaped circuit and merge with a second water stream at the Y-junction. The combined flows of droplets in oil and water travel in parallel streams toward a triangular guidepost that diverts the lipid-coated droplets into the parallel water stream. As the droplets cross the oil-water interface, a second layer of lipids deposits on the droplet, forming a bilayer.
The newly created vesicles range from 20 to 70 micrometers in diameter. The entire circuit fits on a glass chip roughly the size of a poker chip.
Researchers also tested the synthetic bilayers for their ability to house a prototypical membrane protein. The proteins correctly inserted into the synthetic membrane, proving that they resemble membranes found in biological cells.
"The lipid membrane assemblies of cells and their organelles pose a daunting challenge to the chemist who wants to synthesize these structures with the same rational approaches used in the preparation of small molecules,” Paegel points out.