Body handles nanofiber better

By Kimberly Patch and Eric Smalley, Technology Research News

Living tissue often reacts to foreign objects by encapsulating them in scar tissue. This is a problem with orthopedic implants like artificial hips and neural implants like electrical probes.

Researchers from Purdue University have made a discovery that may help: carbon nanofibers are surprisingly compatible with human tissue.

Their experiments showed that increasing the amount of carbon nanofibers in a polycarbonate urethane composite implant increased the functions of nerve and bone-forming cells and decreased the function of scar-tissue formation. "My lab has shown increased in vitro tissue regeneration for a number of tissues including bone, cartilage, vascular and bladder," said Thomas J. Webster, an assistant professor of biomedical engineering at Purdue University.

The material could eventually be used to create better bone and neural implants, said Webster.

Carbon nanofibers are woven from carbon nanotubes, which are rolled-up sheets of carbon atoms that are a natural ingredient of soot. Nanotubes have useful electrical properties, are very strong, and are very small. They can be narrower than one nanometer, which is the width of ten hydrogen atoms.

The results imply that compatibility has to do with the size of the fibers that make up the materials. "We believe nano phase materials hold much promise in tissue regeneration since tissues in our bodies are nanostructured" themselves, said Webster. "Cells in our bodies are accustomed to interacting with surfaces with many nano features," he said. "Nano materials can duplicate such architectures."

The researchers have also shown that other materials that contain surfaces with nano-size features are also more compatible with the human body. "A wide range of materials that contain nano features, including metals, ceramics, polymers and composites," has shown increased in vitro tissue regeneration, according to Webster. "We believe this opens a wide new door for all nano materials in tissue engineering applications," he said.

Potential practical applications include coatings for orthopedic implants like hip and ankle replacements. "Materials are badly needed which can obtain a firm attachment with bone tissue," said Webster. "The current average lifetime of... orthopedic implants is only 15 years," he said. "Carbon nanofibers/nanotubes may be one of those materials."

Carbon nanofibers are especially appropriate as a material to make up electrodes that could monitor or repair electrical activity in the brain. Currently silicon electrodes are used for this purpose, but they tend to induce scar tissue, which keeps the electrodes from making contact with neurons. "This study suggests that such scar tissue can be decreased by using small nano-dimension carbon nanofibers," said Webster.

Carbon nanotubes also have strong electrical properties. "These carbon nanofibers also interact with neurons, which means if used as electrodes they can establish electrical connection with the brain," Webster said.

Carbon nanofiber materials could be used in orthopedics in five to ten years, but it will be one to two decades before neural applications are practical, said Webster.

The next step in exploring the use of the material for establishing electrical connection with neural tissue is animal studies, said Webster. "A lot needs to be done to achieve these final results," said Webster. "The in vitro environment is quite different from the in vivo environment," he added.

Webster's research colleagues were Michael C. Waid, Janice L. McKenzie, Rachel L. Price and Jeremiah U. Ejiofor. The work appeared in the January, 2004 issue of Nanotechnology. The research was funded by the National Science Foundation (NSF) and the Purdue Research Foundation.

Timeline:   5-10 years, 10-20 years
Funding:   Government; University
TRN Categories:   Nanotechnology; Biotechnology; Materials Science and Engineering
Story Type:   News
Related Elements:  Technical paper, "Nano-Biotechnology: Carbon Nano Fibers As Improved Neural and Orthopedic Implants" Nanotechnology, January, 2004


December 17/24, 2003

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