Aug. 10, 2009 -- A new procedure to turn blocks of wood into artificial bones has been developed by Italian scientists, who plan to implant them into large animals, and eventually humans.
Wood-derived bone substitute should allow live bones to heal faster and more securely after a break than currently available metal and ceramic implants.
The researchers chose wood because it closely resemble the physical structure of natural bone, "which is impossible to reproduce with conventional processing technology."
"Our purpose is to convert native wood structures into bioactive, inorganic compounds destined to substitute portions of bone," said Anna Tampieri, a scientist at the Instituto Di Scienza E Techologia Dei Materiali Ceramici in Italy.
To create the bone substitute, the scientists start with a block of wood -- red oak, rattan and sipo work best -- and heat it until all that remains is pure carbon, which is basically charcoal.
The scientists then spray calcium over the carbon, creating calcium carbide. Additional chemical and physical steps convert the calcium carbide into carbonated hydroxyapatite, which can then be implanted and serves as the artificial bone.
The entire process takes about one week and costs about $850 for a single block. One block translates to about one bone implant.
The researchers also note that they can create virtually any size or shape.
Wood-based implants would have several advantages over traditional titanium or ceramic implants, says Tampieri. Since their physical structure is more spongy than solid, like many metal or ceramic implants, live bone should grow into wood-derived bone substitute quicker and more securely.
"One disadvantage (of titanium) is that its not bioactive," said Frank Muller, a researcher at the Institute of Materials Science and Technology in Germany. This means that titanium is unable to interact with living tissue, unlike the wood-derived substitute.
"When implanted into the body, it is encapsulated by fibrous tissue. But if you introduce pores into the titanium. the mechanical properties can be compromised." If the titanium is weakened, it may break, leading to further damage to the bone.
Paradoxically, metal or ceramic implants meant to prevent bone breaks can sometimes cause them. Current implants are significantly harder than the bone that surrounds them. Natural bone can flex slightly. In fact, stress helps build stronger bones. However, the harder implants can apply so much stress to a particular area that the bone snaps. Softer wooden implants might cause fewer bone breaks.
However, wood-derived bone substitute are still not cleared for use in humans. The scientists are currently limited to sheep. Application in humans is likely years away, says Tampieri.
For now, however, wood-derived materials may be put to other use.
"Materials able to maintain adequate properties at extremely high temperatures and mechanical stress are highly sought after for use in several different applications, " said Tampieri. "Including, for example, catalytic silencers, space vehicles, turbine equipment for power generation plants and aircraft engines, like turbine blades, vanes, shrouds, and combustor components, and metal forming and glass blowing equipment."
Muller agrees that, until wood-derived bone subtitutes are available to humans, there are many other potential applications for these materials.
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