This drop looks very similar
to the sac formed
by the self-assembly
of small and large molecules
Imagine having one polymer and one small molecule that instantly assemble into a flexible but strong sac in which you can grow human stem cells, creating a sort of miniature laboratory.
And that sac, if used for cell therapy, could cloak the stem cells from the human body’s immune system and biodegrade upon arriving at its destination, releasing the stem cells to do their work.
Researchers created these sacs. They report that the sacs can survive for weeks in culture and that their membranes are permeable to proteins. Proteins, even large ones, can travel freely across the membrane.
This new and unexpected mode of self-assembly also can produce thin films whose size and shape can be tailored. The method holds promise for use in cell therapy and other biological applications as well as in the design of electronic devices by self-assembly, such as solar cells, and the design of new materials.
“We started with two molecules of interest, dissolved in water, and brought the two solutions together,” said Samuel I. Stupp who led the research.
“We expected them to mix, but, much to our surprise, they formed a solid membrane instantly on contact. This was an exciting discovery, and we then proceeded to investigate why it happened. Understanding the surprising molecular mechanism was even more exciting.”
Having formed the sacs, Stupp and his team next studied human stem cells engulfed by the self-assembly process inside sacs that they placed in culture. The researchers found that the cells remained viable for up to four weeks, that a large protein could cross the membrane, and that the stem cells were able to differentiate.
“The membrane is a fascinating and unusual structure with a high degree of hierarchical order,” said Stupp. “The membrane grows through a dynamic self-assembly process which generates hybrid nanofibers made up of both molecules and oriented perpendicular to the plane of the membrane. This architecture is very difficult to get spontaneously in materials. Using the right chemistry, the thick membrane structure could be designed to get conduits of charge in solar cells or nanoscale columns of catalytic nanostructures that would extend over arbitrary macroscopic dimensions.”
While the underlying, highly ordered structure of the sacs and membranes has dimensions on the nanoscale, the sacs and membranes themselves can be of any dimension and are visible to the naked eye.
COMPAMED.de; Source: Northwestern University