A microfluidic technique has been used to create a source of unilamellar, uniformly sized vesicles
Vesicles — amphiphilic-membrane-bound 'bubbles' of liquid — can be used as drug-delivery vehicles and as bioreactors. Now Shoji Takeuchi and co-workers at the University of Tokyo have developed1 a high-throughput microfluidic technique that produces hundreds of unilamellar vesicles per minute, of uniform size and with high encapsulation efficiency.
The technique uses a lithographically created poly(dimethylsiloxane) device in which a series of small chambers are built into the walls of a larger channel. The main channel is first filled with an aqueous solution, which then fills the smaller chambers, and later comprises the contents of the vesicles. An oil containing phospholipids then flushes the aqueous solution out of the main channel, and is followed by another aqueous solution. This results in a phospholipid bilayer plugging the small chambers and separating the two aqueous phases.
The aqueous fluid in the small chambers is then gently forced out towards the main channel. At the same time another fluid is flowed perpendicularly through the main channel, deforming the bilayer until part of it finally breaks away from the membrane to form a vesicle, in a technique similar to blowing bubbles. The unilamellar vesicles are approximately the size of a cell, have a narrow size distribution and were shown to function as bioreactors.
Ota, S., Yoshizawa, S. & Takeuchi, S. Microfluidic formation of monodisperse, cell-sized, and unilamellar vesicles. Angew. Chem. Int. Ed. 10.1002/anie.200902182 (2009).