At Northwestern University researchers discovered an interesting relationship between two molecules, in which their interaction forms a solid membrane that seems to be quite suited for creation of small sacs to host all kinds of cells in biological solutions, including possibly stem cells. The material might also have wider medical applications:
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.
“We started with two molecules of interest, dissolved in water, and brought the two solutions together,” said Samuel I. Stupp, Board of Trustees Professor of Materials Science and Engineering, Chemistry and Medicine, 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.”
One of the molecules is a peptide amphiphile (PA), small synthetic molecules that Stupp first developed seven years ago, which have been essential in his work on regenerative medicine. The other molecule is the biopolymer hyaluronic acid (HA), which is readily found in the human body, in places like joints and cartilage. Stupp recently had started a new research project on the regenerative medicine of cartilage, which drew him to hyaluronic acid.
“This is a clear example of informed discovery,” said Stupp, director of the Institute for BioNanotechnology in Medicine. “We knew there was something interesting about the interaction between peptide amphiphiles and biopolymers from our previous work on nanostructures that can cause blood vessels to grow. And we were particularly interested in hyaluronic acid because of its role in cartilage, a tissue that adults cannot regenerate and, when damaged in joints, causes grief to humans.”
Using just these two molecules, Stupp and his team can make many different structures, the two most important being sacs, which have a solid membrane on the outside and liquid inside, and flat membranes of any shape. The researchers can make the structures large or small, pick up the material with tweezers, stretch it and even easily repair the sacs through self-assembly should the material tear or have some other defect. The sacs also are robust enough to be sutured by surgeons to biological tissues.
Press release: Self-Assembled Materials Form Mini Stem Cell Lab…
Video: Self-assembling sacs form instantly when two aqueous solutions, one containing small molecules (first drop) and another containing high molecular weight polymers (green drop), are brought together….