EVANSTON, Ill. --- 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.

Futuristic? Only in part. A research team headed by Samuel I. Stupp, Board of Trustees Professor of Materials Science and Engineering, Chemistry and Medicine, who led the research from Northwestern University’s Institute for BioNanotechnology in Medicine has created such sacs and demonstrated that human stem cells will grow in them. The researchers also 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, to be published March 28 in the journal Science, 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.