Human pluripotent stem cells, which can differentiate into any other kind of body cell, hold great potential to treat a wide range of ailments, including Parkinson’s disease and multiple sclerosis. However, scientists who work with such cells have had trouble growing large enough quantities to perform experiments.

And should a promising treatment be developed, researchers would have concerns about testing it, because most materials now used to support the growth of human stem cells include cells or proteins derived from mouse embryos. These materials would probably cause an immune reaction if injected into a human patient.

To overcome those problems, MIT chemical engineers, materials scientists, and biologists have devised a synthetic surface, free of any animal material, that can be used as a substrate for growing stem cells. It enables them to stay pluripotent for at least three months; cells grown on the materials now used can start to differentiate after a week.

It is also the first synthetic material that allows single stem cells to form colonies of identical stem cells, which makes it much more feasible to identify cells that have successfully become pluripotent. In the future, this should also make it easier to screen for cells that have developed into different cell types, such as heart or lung cells.

Previous studies had suggested that several properties of surfaces–including roughness, stiffness, and affinity for water–might influence how well stem cells grow. The MIT team created about 500 polymers (long chains of repeating molecules) that varied in those traits. Then they grew stem cells on them and analyzed each polymer’s performance. They found an optimal range of surface hydrophobicity (water-repelling behavior), but varying roughness and stiffness did not have much effect on cell growth.

Using their best-performing material, the researchers got stem cells to continue growing and dividing for up to three months. They were also able to generate millions of cells–enough to do the large-scale experiments needed to develop potential therapies. The technique works both with embryonic stem cells and with body cells that have been reprogrammed to mimic an immature state.

The MIT researchers now hope to refine their knowledge to help them build materials suited to other types of cells, such as adult stem cells, says senior author Daniel Anderson, of the MIT Department of Chemical Engineering, the Harvard-MIT Division of Health Sciences and Technology, and the David H. Koch Institute for Integrative Cancer Research. “We want to better understand the interactions between the cell, the surface, and the proteins and define more clearly what it takes to get the cells to grow,” he says.