Technique could offer solutions for current limitations of static substrates used in bioengineering.

Scientists report that they used shape memory polymers (SMPs) to study how cells sense and respond to their physical environment. They were able to show that cells remained viable when substrate topography was changed and that the cells responded to the change.

Most cell biomechanics research has used unchanging, flat surfaces. “Living cells are remarkably complex, dynamic, and versatile systems, but the material substrates currently used to culture them are not,” says James Henderson, Ph.D., assistant professor of biomedical and chemical engineering in Syracuse University’s L.C. Smith College of Engineering and Computer Science and researcher in the Syracuse Biomaterials Institute. “What motivated our work was the need for cell culture technologies that would allow dynamic control of cell-material interactions.”

The goal of Dr. Henderson’s research was to develop a temperature-sensitive SMP substrate that could be programmed to change shape under cell-compatible conditions. SMPs are a class of materials that can switch between two shapes on command, from a fixed (temporary) shape to a predetermined permanent shape, via a trigger such as a temperature change.

The breakthrough needed to achieve this aim was made by Kevin Davis, a third-year Ph.D. student in the Henderson lab. Davis developed an SMP with a transition temperature that worked within the limited range required for cells to live. He observed greater than 95% cell viability before and after topography and temperature change.

After confirming that cells remained viable on the substrate, Davis then investigated the changes in cell alignment on the surface that results from topography change. He programmed an SMP substrate that transitioned from a micron-scale grooved surface to a smooth surface.

When the cells were seeded on the grooved sample at 30ºC, they lined up along the grooves of the surface. The substrates were then placed in a 37ºC incubator, which was the transition temperature for the substrate to recover to a smooth surface. Following shape memory recovery, the cells were observed to be randomly oriented on the substrate.

The next phase of this research is to move from a 2-D substrate to a 3-D substrate and examine cell viability. Additionally, Dr. Henderson’s team will be looking at what is going on inside the cells as a result of topography changes.

“For the first time we’ve shown that this general concept can be used successfully with cells, which suggests that it can be extended to a number of biomaterials that could be used for scaffolds and many other applications,” says Davis. Since most scaffolding is made out of polymers, Dr. Henderson envisions one day using SMPs to create scaffolds that can expand inside the body, allowing for less invasive surgical procedures.

Dr. Henderson’s team collaborated with Kelly Burke, Ph.D., of Case Western Reserve University and Patrick T. Mather, Milton and Ann Stevenson professor of biomedical and chemical engineering at Syracuse University. Their results were highlighted in the January issue of Biomaterials. The paper is titled “Dynamic cell behavior on shape memory polymer substrates.”

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