Pop a bubble while washing the dishes and you're likely to release a few drops of water trapped when the soapy sphere formed. A few years ago, researchers at the National Institute of Standards and Technology (NIST) pioneered a method* using a microscopic fluidic (microfluidic) device that exploits the same principle to create liquid-filled vesicles called liposomes from phospholipids, the fat complexes that are the building blocks for animal cell membranes. These structures are valued for their potential use as agents to deliver drugs directly to cancers and other disease cells within the body.
Widespread application of liposomes as artificial drug carriers has been hindered by a number of limiting factors such as inconsistency in size, structural instability and high production costs. In a new study,** the NIST and University of Maryland (UM) researchers have detailed the operation of their liposome manufacturing techniqueknown as COMMAND for COntrolled Microfluidic Mixing And Nanoparticle Determinationin order to maximize its effectiveness. Their goal was to better understand how COMMAND works as it produces liposomes with diameters controlled from about 50 to 150 nanometers (billionths of a meter) that are consistently uniform in size and inexpensively produced in what might be called an "assembly-line-on-a-microchip."
The researchers fabricate the COMMAND microfluidic devices by etching tiny channels into a silicon wafer with the same techniques used for making integrated circuits. In COMMAND, phospholipid molecules dissolved in isopropyl alcohol are fed via a central inlet channel into a "mixer" channel and "focused" into a fluid jet by a water-based solution (that in production would carry a drug or other cargo for the vesicles) added through two side channels. The components blend together as they mix by diffusion across the interfaces of the flowing fluid streams, directing the phospholipid molecules to self-assemble into nanoscale
|Contact: Michael E. Newman|
National Institute of Standards and Technology (NIST)