Originally Published MDDI October 2005
Single-walled carbon nanotubes may be able to strengthen bone tissue, producing tougher and more flexible artificial bone implants.
Researchers at the University of California's Riverside campus saw carbon nanotubes as a replacement for natural collagen in bones because it is one of the strongest known materials on Earth.
Above, hydroxyapatite crystal is grown on a coated nanotube surface. The larger photo shows the hydroxyapatite's well-organized structure, which is preferred for natural bone growth. Photos supplied by the University of California at Riverside.
“Collagen is based on carbon materials, so it's not a big stretch,” says Robert Haddon, professor of chemistry and chemical engineering at UC Riverside. Collagen fibers and nanotubes are also about the same size—a nanometer.
Bone tissue is composed of organic and inorganic materials, which form a strong and flexible composite structural material. The inorganic ingredient is a calcium-based mineral called hydroxyapatite. Researchers found that carbon nanotubes can play the organic part, imitating the role of collagen in bones.
The nanotubes were chemically treated to attract calcium ions and produce the growth of hydroxyapatite crystals on their surfaces. This also increased the nanotubes' biocompatibility by making them more water-soluble. The results indicated that carbon nanotubes could act as a scaffold for inducing the growth of hydroxyapatite crystals, just like collagen does.
Researchers need to conduct strength and biocompatibility testing on the material before they can start looking at ways to change the balance between nanotubes and minerals. Other uses for the nanotubes will become clearer once clinical tests are performed.
Complications with current artificial bone scaffolds include low strength and possible rejection by the body. Haddon suggests that the next step may be to find a medium in which one could grow bone, inject the carbon nanotubes into the bone, and then observe their incorporation into the naturally grown bone. Based on the success of further research, the nanotubes could help heal broken bones. However, Haddon stresses that work is still in its early stages.
The team published its findings in the June issue of the American Chemical Society's Chemistry of Materials.
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