Researchers are aware that cells on flat surfaces have skewed metabolisms, gene expression and growing patterns. But the only choices have been glass labware and a product called Matrigel, a gelatinous protein mixture secreted by mouse tumor cells. While Matrigel does resemble a complex extracellular environment, it also contains growth factors and unknown proteins that limit its desirability for experiments requiring precise conditions.
"Synthetic biopolymer microfiber scaffolds have been studied for more than 30 years to mimic a living 3D microenvironment, but concerns exist about their degradation products and chemicals," the authors wrote in the paper.
Other synthetic polymer biomaterials are simply too big. Getting cells to grow on them is like forcing spiders to build webs on skyscraper girders. Zhang's nanofiber scaffold, around 1,000 times smaller than the existing systems, is much closer in size to the extracellular matrices that living cells manufacture themselves.
With the addition of defined amino acid fragments called active motifs, the scaffold can be fashioned to coax stem cells to behave in certain desirable ways-such as differentiating into needed body tissues or migrating toward bone marrow and other natural destinations.
"What makes these designer scaffolds particularly interesting is that cells survive longer and differentiate better without additional soluble growth factors," Zhang said. "This suggests that extracellular microenvironments may play a more important role for cell survival and for carrying out cell functions than previously thought."