CHAMPAIGN, Ill. -- By manipulating simple and nonspecific interactions, researchers have discovered a way to make chemicals spontaneously self-assemble into ribbon-like tubules that resemble bacterial cell walls. The micrometer-sized tubules have potential applications in drug delivery systems and as templates for the synthesis of inorganic nanostructured materials.
"The 'artificial bacteria' consist of the biopolymer actin attached to charged lipid membranes," said Gerard Wong, a professor of materials science and of physics at the University of Illinois. Wong was the lead author of a paper published in the June 16 issue of the journal Science that described the assembly process. "The resulting actin-membrane capsules are fairly rigid and quite stable," he said.
Actin is a protein that provides the structural framework in eukaryotic cells and forms the molecular basis for biological functions as diverse as hearing, muscle contraction and cell division. When mixed with special liposomes, the researchers found, actin immediately undergoes a hierarchical self-assembly process that results in the formation of nano-scale tubular capsules.
"The composite membrane is organized into three layers," Wong said. "A middle lipid layer, similar to the plasma membrane that surrounds most cells, is sandwiched between two layers of actin filaments. The filaments first arrange themselves into two-dimensional parallel arrays on both sides of the lipid layer, and then they spontaneously wrap into tubules."
The spaces between the layers are filled with water and could be used for a variety of applications, including the packaging of certain drugs that would be slowly released to the body. The nano-capsules also could be used as miniature templates in novel, inorganic nanofabrication techniques.
While the structures have no real analog in nature, this type of spontaneous organization is reminiscent of multi-layered bacterial cell walls, Wong said. The protein-
Contact: James E. Kloeppel, Physical Sciences Editor
University of Illinois at Urbana-Champaign