The two-layer, fully biocompatible structure made from protein strands of elastin is able to contract by expending chemical energy and then reassuming its original shape.
Scientists at the University of Freiburg in Germany have created an artificial muscle made of elastin, a common animal protein. It is able to contract under the influence of temperature and acidity and is fully biocompatible. Theoretically, such muscles could find future applications in regenerative medicine, restoring fragments of irreversibly lost tissue. Stefan Schiller and his colleagues write about it in an article published in the journal Advanced Intelligent Systems.
Elastin is a fibrillar protein that resembles long threads and is part of connective tissue. It forms an intercellular skeleton that supports cell structures, guides cell growth and migration of individual cells. It is elastin that gives elasticity to the skin, vascular walls, bladder and other tissues. Scientists in Freiburg slightly altered the amino acid sequence of elastin to yield two similar molecules, one responsive to the acidity (pH) of the medium and the other to temperature; using photochemical reactions, the two chains are fused into a two-layer structure.
In the presence of a chemical energy source (in this case, sodium sulphite), such proteins are able to reversibly change their structure. Following fluctuations in pH, one of them contracts and stretches again, forcing the whole such muscle to bend now and then take its original shape, converting chemical energy into mechanical motion. An additional temperature effect can turn these fluctuations "on" and "off", giving the artificial muscle a "memory effect".
According to scientists, in future it will be possible to create analogues of this system, capable of reacting also to other environmental stimuli, and also using other chemical compounds as energy sources. Programmable muscles may find application not only in medicine, but also in robotics. In the meantime, machine designers are experimenting with living muscle cells to drive their own devices.
