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   from the issue of April 13, 2006

One-step process creates synthetic bone


Scientists for years have tried to create a composite that can replace bone.

BONE REPLACEMENT - UNL chemist Jody Redepenning hopes to develop a biocomposite material that can reinforce or replace bones like the...
 BONE REPLACEMENT - UNL chemist Jody Redepenning hopes to develop a biocomposite material that can reinforce or replace bones like the one in his hand. Photo by Kelly Bartling/University Communications.

A chemistry professor at UNL has done just that: By discovering a simple process that no one else knew would work, chemist Jody Redepenning has discovered a monomer that, when heated, becomes as hard as bone. That finding can lead to a biocomposite that can be used as a bone replacement, a screw, or other orthopedic appliances or hard-tissue replacements.

What's more, the body will absorb the material and it effectively becomes part of the bone surrounding it.

"What we do is we simply take pure hydroxyapatite, the inorganic part of bone, and we take the pure monomer, we dump them together and we heat them up, and in one step it goes to this composite of hydroxyapatite/polylactide," Redepenning said. "There's no solvent or catalyst or purification step. In one step it gels and solidifies and becomes this hard object."

The hydroxyapatite used for these composites can be synthesized in powdered form or can be derived from bone. The bone is heated in air at 1,500 degrees Fahrenheit to removed the organic components, leaving a porous hydroxyapatite lattice. When the monomer is exposed at appropriate temperature to the hydroxyapatite lattice, it fills the pores and polymerizes there to give a composite withi a physical appearance and mechanical properties similar to the original bone.

The monomer, L-lactide, is made in Nebraska from the ethanol refining process - from corn. It is not a new discovery, but the fact that it becomes a polymer when heated with hydroxyapatite, is.

"It's cheap and easy and completely unsophisticated," Redepenning said. "The technique involves cooking or heating it up; no solvent or purification is needed."

Many biomaterials have been created with mixtures of other polymers, but the hydroxyapatite discovery is unique.

The biocomposite material is easily molded into appliances or pieces useful in bone or hard tissue repair, such as screws.

"Ultimately the repair process would involve reabsorbing the screws and redepositing the material that was in the screws as living bone... over the course of several years, they're completely reabsorbed," Redepenning said.

Reddepenning is "tweaking" the process to find the best reaction conditions and applications.

"There are other composites that might work well with this biomaterial. Eventually we could come up with something that's actually stronger than bone," Redepenning said.

The process has a patent pending. It was one of several technologies featured this week at an international BIO biotechnology conference in Chicago.

Research Focus

"Research Focus" is a Scarlet feature highlighting research projects at UNL. For more information, call 472-8515 or send e-mail to



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