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Shape-Sifting: NIST Categorizes Bio Scaffolds by Characteristic Cell Shapes

From NIST Tech Beat: February 7, 2014

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Contact: Michael Baum


cell scaffolding graph composite
(Top) The same basic cell type grown on two different bio scaffolds (collagen gel and a grid-like scaffold made of a biocompatible polymer) adopts significantly different shapes. The superimposed ellipsoids are calculated from the dimensions of each cell. (Bottom) Plotting the characteristic ellipsoids for each cell by how round they are in the two major cross sections reveals that cells tend to different shapes on different scaffolds--spheres at one extreme, long narrow rods at another.
Credit: Farooque, Camp, Simon/NIST
high resolution image

With the notable exception of Flat Stanley, we all live, and are shaped by, a 3-dimensional world. Biologists have accepted that this dimensional outlook is just as important to growing cells. A key challenge in tissue engineering—the engineering of living cells to grow into replacement or repair tissues such as bone, heart muscle, blood vessels or cartilage—is creating 3-D scaffolds to support the cells as they grow and provide an appropriate environment so that they develop into viable tissue.**



The NIST team made painstaking measurements of individual cells in a variety of typical scaffolds using a confocal microscope, an instrument that can make highly detailed, 3-dimensional images of a target, albeit with very lengthy exposure times. They then used a mathematical technique—"gyration tensors"—to reduce each cell's shape to a characteristic ellipsoid. Ellipsoids can range in shape from points or spheres to flat ellipses or elongated sticks to something like an American football.



**See, for example, the NIST news stories "Scaffold Gradients: Finding the Right Environment for Developing Cells" (May 2010) at and "NIST Announces New Scaffold Reference Material for Tissue Engineering Research" (June 2013) at NIST work on 3D Tissue Scaffolds is described at
***Poly(ethylene glycol) tetramethacrylate.