Harder, Better, Faster, Stronger (Bones)

Carbon nanotubes, the jack-of-all-trades of the nano world, have made another successful foray into the biomedical realm. In the art of substituting damaged hips and knees with metal hinges, success depends on an implantâ''s ability to coax bone to grow onto it. Now, a group of biomedical engineers at Brown University have found that the titanium implants bond more successfully when there are carbon nanotubes thrown in the mix.

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[image credit Sirinrath Sirivisoot/Brown University]

These engineers, led by Thomas Webster, treated the metal to create a porous coating on the titaniumâ''s surface. They then deposited a catalyst inside the pits, heated the material and waited as carbon nanotubes began to sprout. (Carbon nanotubes can vary in size, but for a sense of scale, some are being grown at 1/10,000th the diameter of a human hair.)

They then placed bone-forming cells, called osteoblasts, onto the treated titanium. Three weeks later, the Brown team found that the bone cells grew twice as fast on the nanotube-covered titanium and also made more calcium than on the ordinary titanium. Calcium, as we all know, is an important component of healthy bones.

Since their discovery, carbon nanotubes have held great promise for biomedical applications. They exhibit a number of unique properties, including a very ordered structure with high surface area, mechanical strength, electrical conductivity and thermal conductivity. Within medicine, theyâ''re also being explored as a substrate for growing cells for tissue regeneration, as transport systems for drugs in the pharmaceutical industry and as a vector for introducing foreign material into cells.

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