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MATERIALS scientists at the University of Washington have developed a three-dimensional stem cell scaffold made from the natural materials chitosan and alginate.

The chitosan and alginate scaffold mimics stem cells’ natural binding sites, and as it is porous, stem cells can attach and develop throughout the structure. It was developed by a team lead by Miqin Zhang, a professor of materials science and engineering. Chitosan, made from the shells of crustaceans such as prawns and crabs, and alginate, derived from algae, are already approved for use by the US Food and Drug Administration for food and biomedical applications.

In initial tests the prototype scaffold was seeded with 500,000 human embryonic stem cells. After just 21 days, the scaffold was found to be saturated with cells. The stem cells can be easily retrieved by dissolving the scaffold, which is biodegradable, in a mild solution. Throughout the 21-day period the cells were assessed in vitro, by looking at growth rates, gene activity and functionality, and in vivo by implantation into mice. Pluripotency (ability to form many types of cell) was verified by further culture of the stem cells for 14 days.

The researchers say that as well as dissolving the scaffold to retrieve the stem cells, it could be implanted directly into the body as it would simply biodegrade. The technique has significant advantages as it avoids the need for animal-derived feeder layers, which were found in 2005 to contaminate stem cells. Changing the processing method for the scaffold could create different-sized pores suitable for growing different cells.

"The major challenge for stem cell therapy today is it's very difficult to make a lot of them with high purity," says Zhang. "So far it seems like this material is very good for stem cell renewal." 

Her team is now working on scaling up the prototype. They will also try to grow other stem cells, such as those from umbilical cord blood and bone marrow in the scaffold, in collaboration with Washington’s Institute for Stem Cells and Regenerative Medicine and the School of Medicine.

The research was published in Biomaterials (doi: 10.1016/j.biomaterials.2009.09.070).