The study led by Associate Professor Thomas Webster shows that for orthopaedic implants to be successful, bone must meld to the metal that artificial hips, knees and shoulders are made of. He says that the new material may help increase this success rate.
During the study, titanium, the most popular implant material, was chemically treated and exposed to electrical currenta process called anodization that created a pitted coating in the surface of the metal.
The researchers packed the pits with a cobalt catalyst, and heated them to a scorching 700° Celsius with the help of chemicals. The process caused carbon nanotubes to sprout from each pit.
Bone-forming cells, known as osteoblasts, were then placed on the nanotube-covered samples and on samples of plain and anodized titanium. Thereafter, the samples were placed in an incubator.
Three weeks later, the researchers found that the bone cells grew twice as fast on the titanium covered in nanotubes. Cells interacting with the nanotubes also made significantly more calcium, which is an essential ingredient for healthy bones.
"What we found is possibly a terrific new material for joint replacement and other implants," said Webster, associate professor of engineering at Brown.
"Right now, bone doesn't always properly meld to implants. Osteoblasts don't grow or grow fast enough. Adding carbon nanotubes to anodized titanium appears to encourage that cell growth and function," he said.
Webster hopes that the new material can lead to a new class of implants, which can sense bone growth and send information about the same to an external device. Such a technology may enable doctors to monitor the output, and to determine whether to inject growth hormones or otherwise intervene to avoid additional surgery, he says.
He feels that such "biosensing" implants may even be designed to detect infection, or may be specially coated to release antibiotics or other drugs into the body.
According to Webster, the biosensing concept may work because an electrical current is created when cells make calcium, and that current can be conducted through carbon nanotubes and transmitted via radio frequency to a handheld device outside the body. The process will be similar to one that is employed by state-of-the-art cardiac pacemakers, he says.
"This technology would be incredibly exciting. It could significantly improve patient health - and cut down on expensive diagnostic tests and surgery. We still have a long way to go to make an intelligent implant a reality, but our new results are a strong first step," Webster said.
The study has been published in the journal Nanotechnology.