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Every year, millions of Americans injure a joint or break a bone. Now, as this ScienCentral News video explains, one researcher says that instead of replacing bone, he has found a material that might help bone grow back.
Ann Doherty and her husband Bill have unfortunately found out just how difficult it can be. They have both had knee replacement surgery and although it has helped them tremendously, they sometimes still feel the pain and discomfort of their false knee. The stainless steel knee matches bone's strength and keeps them up and about, but it doesn't have the same flexibility that bone has. "I can't kneel down," says Bill. "If I get down on the floor it's hard for me to get up." Ann, who also has rheumatoid arthritis, says, "It feels like a knee except when you have to kneel. And the skin is a little thin there and it's difficult."
While both, Ann and Bill are not letting this get in the way of living out their retirement years, one researcher is thinking of alternatives to artificial replacements. In fact, materials scientist Robert Haddon of the University of California, Riverside and his team hope to someday grow bone back — using carbon nanotubes. A nanotube is essentially a sheet of carbon atoms linked to each other in a chicken wire structure and rolled into a tiny cylinder, one ten-thousandth the width of a human hair.
"If you're thinking of a material for bone growth," Haddon explains, "what you have to do is come up with some sort of structure that is going to have, at it's core, a very strong fiber." In our body, that fiber is a protein called collagen that supplies structural strength. Because the arrangement of carbon atoms in a nanotube makes it extremely strong, Haddon hypothesized that it could work in place of collagen. Also to its advantage, over metal, nanotubes are very flexible.
But bone is a composite of collagen, which makes up the organic part, and the inorganic part, which is a mineral called hydroxyapatite. Collagen acts as a scaffold, attracting these minerals to grow on its surface to make bones strong. "So if you want to regenerate bone, you have to find a way to grow this hybrid material," explains Haddon.
Therefore, for nanotubes to mimic bone completely they would have to attract calcium ions and initiate the growth of hydroxyapatite. To do this Haddon treated the nanotubes with different chemicals and was able to tailor the nanotube so that it had a number of chemical groups attached to them. This allowed them to attract the necessary minerals as well as made them water-soluble.
While there have been concerns that nanoparticles might pose a health problem, Haddon hopes to work with physicians so that the tailored nanotubes can be tested in people for compatibility and safety. "One of the things, we'd really like to do with this is we'd like to have the ability to work with people in the clinical setting to just evaluate if it really has any potential," says Haddon. While he cautions that the research is at a very early stage, he envisions that if everything works out right, healing a fracture would simply mean you would make a solution of the tailored nanotubes and "you could simply inject this into the region of the fracture," and let the nanotubes help the body's natural healing process along.
He hopes further research will give people like Ann and Bill another solution to their aching joints.