Wood Biomimics Bone For More Functional Prosthetics
Hydroxylapatite is an inorganic mineral that comprises 70 percent of human and animal bone. The mineral, which can be obtained from other sources, is often used as prosthetic implants for amputated or lost bone to act as a filler and to provide a structure to encourage bone to grow into the prosthetic device. For the first time, inspired by a tree's hierarchial structure of growth, Italian scientists have created bone prostheses from wood.
Anna Tampieri and her colleagues at the Institute of Science and Technology for Ceramics in Faenza, Italy, found that the natural scaffolding of wood, with its similarity to real bone, would be a more natural way to encourage the growth of real bone. Such an architecture has not been present in the other materials used to create hydroxylapatite, making those prosthetic devices inable to support the body's full weight and stresses.
Tampieri and her team heated the wood to decompose the organic parts, which left behind the internal architecture of the wood, essentially a template for the prosthesis. The resulting structure was exposed to calcium, oxygen, and then carbon dioxide to form calcium carbonate, after which it was converted to hydroxyapatite using a phosphate donor.
The internal architecture of the wood prosthetic, though not identical to that of bone, is similar enough to allow the cells and blood vessels to grow through the wood, providing better assimilation of the prosthetic and giving it the strength it needs to carry the body weight and stresses it needs to be effective.
Tampieri said the applications for wood hydroxylapatite did not stop at prosthetics for bone. "Materials able to maintain adequate properties at extremely high temperatures and mechanical stress are highly sought after for use in several different applications, such as space vehicles,' she commented. 'An intriguing possibility is that of simultaneously achieving high values of strength and toughness, for which ordinarily there is a trade-off. In addition, new materials with extreme physical properties, such as thermal expansion or piezoelectricity, can be obtained."