Engineering membranes from cellular parts.

Chemists have for the first time spun fibrous networks out of the molecules that make up cellular membranes. The engineered membranes may eventually be used as biocompatible drug-delivery devices or antimicrobial coatings for fabrics or other surfaces.

Phospholipids are molecules that contain a water-attracting chemical group attached to a water-repelling chemical tail. In a cellular membrane, the water-attracting groups, which are exposed to the aqueous cellular environment, sandwich an inner core of water-repelling tails.

Timothy E. Long of Virginia Polytechnic Institute and State University in Blacksburg and his colleagues investigated whether they could manipulate phospholipids with a laboratory technique called electro-spinning, which is typically used to process polymer solutions into nanoscale-diameter fibers. In this technique, says Long, researchers apply a voltage to a polymer-filled syringe and spray the cotton candy-like fibers onto a surface.

The group added lecithin, a natural mixture of phospholipids, to an oily solvent. In such a solution, the phospholipids organize into spheres with their water-repelling tails on the outside and their water-attracting groups at the core. With increasing concentrations of lecithin, the spheres coalesced to form tubular structures.

Using a 45 percent lecithin solution, the team spun the phospholipids into fibers and deposited them onto a metal surface, creating a 7-by-15-centimeter membrane. Under a microscope, the membrane revealed a porous network of fibers that had an average diameter of 3 micrometers. The researchers report their work in the Jan. 20 Science.--A.C.