Researchers at Northwestern University in Chicago have developed a new, superflexible material that can be 3D printed to surgically repair bone breaks. The new “hyperelastic bones” could present a quicker and more affordable option for surgically repairing broken bones. The material can be implanted under the skin, as either a scaffold to facilitate the growth of new bone, or used to replace bone matter itself. So far only tested in animals, researchers have reported “astounding” results.

The material was described in a study, published on September 28th in Science Translational Medicine. It was developed by material science engineer Ramille Shah and his colleagues at Northwestern. It is made from a naturally occurring mineral, called hydroxyapatite, a calcium found in human bones and teeth, mixed with elastic polymer to increase flexibility and durability.

Shah noted “The first time that we actually 3D printed this material, we were very surprised to find that when we squeezed or deformed it, it bounced right back to its original shape,” which means it can be cut, folded, and pressed into areas with missing bone material, without the use of adhesive. Furthermore, the material is porous and absorbent, which allows veins and capillaries to grow into the area. This is essential to prevent the new tissue from dying.

In the study, the researchers inserted human stem cells into 3D printed scaffolds made from the hyperelastic bone material. The cells successfully grew on the scaffolds over a period of weeks, and even produced their own bone minerals.

The researchers also implanted the bone material under the skin of a mouse, and found that the hyperelastic bone integrated quickly with the existing tissue, without any immune system responses or inflammation. The material was also tested in surgical scenarios, including to fuse together the vertebrae of a rat, and to replace unhealthy bone in the skull of a rhesus monkey. In both these situations, the material integrated successfully with existing tissue, and allowed the growth of blood vessels and new bone.

Shah has said he hopes to be able to test the material on humans within five years, after first reproducing these results in larger studies with animals.

The appeal of the hyperelastic bone is not only about its medical properties, but also its relatively cheap and simple production process. Grafts can be tailored to individual patients using 3D printing, and it is easily packaged and shipped, with a shelf life of roughly a year. These properties could make it an ideal solution for developing countries, where it could be shipped ahead of time, and then quickly implemented as needed. The fact that it does not need facilities to keep it frozen or heavily refrigerated is particularly advantageous.

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