Italian scientists have turned wood into bone mimics that could be used to repair damaged limbs.

Turning wood into bone: a new meaning to tree surgery?

Anna Tampieri, at the Institute of Science and Technology for Ceramics, Faenza, and colleagues were inspired by nature's highly organised hierarchial structures to make porous hydroxyapatite scaffolds with structures similar to that of real bone. The scaffolds 'pave the way for realising prosthetic devices which could get closer to the extraordinary performance of human tissues', they claim.

The team heated the wood to decompose the organic parts that make up most of its weight, leaving behind the carbon template. They reacted the template first with calcium, then oxygen and then carbon dioxide to form calcium carbonate. Finally, they converted it to hydroxyapatite using a phosphate donor.

The material keeps its original microstructure, exploiting the unique architectural properties of the wood's cellular make-up, explains Tampieri. This means cells and blood vessels can grow through the structure and incorporate it into the original bone.

'Current [hydroxyapatite] production processes do not generate an organised hierarchical structure,' says Tampieri, adding that this often makes the hydroxyapatite inadequate for bearing the body's weight and managing in vivo stresses.

'This is an interesting study,' says Iain Gibson, an expert in biomedical materials at the University of Aberdeen, UK. 'Although the resulting pore structures obtained do not match those of cancellous (spongy) bone, they provide an interesting first step in proving the concept of using a natural template to produce porous hydroxyapatite scaffolds, and as a potential route to produce biomaterial scaffolds for tissue repair and drug delivery.'

Tampieri says the method could find use beyond tissue engineering. '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 comments. '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.'

Leanne Marle

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