Researchers are scrambling to develop new materials for the orthopedic device industry. For implants to be successful, bone must meld to the metal that artificial hips, knees and shoulders are made of. A team of engineers at Brown University (Providence, RI) have discovered that bone cells are more apt to adhere to a rough carbon nanotube surface than other surfaces.

By using carbon nanotubes and anodized titanium, the engineers recently developed a new material that could significantly increase implant success rates. They took a piece of titanium, chemically treated it and applied an electrical current to it. This process, called anodization, creates a pitted coating in the surface of the titanium.

The engineers packed those pits with a cobalt catalyst and then ran the samples through a chemical process that involved heating them to 700 C. That caused carbon nanotubes to sprout from each pit.

The researchers then placed human osteoblasts, or bone-forming cells, onto the nanotube-covered samples, as well as onto samples of plain and anodized titanium. The samples were placed in an incubator. After three weeks, the team 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 the essential ingredient of healthy bones.

“Bone doesn’t always correctly meld to implants,” says Thomas Webster, an associate professor in the division of engineering and the department of orthopedics. “Osteoblasts don’t grow or grow fast enough. Adding carbon nanotubes to anodized titanium appears to encourage that cell growth and function.”

Webster hopes to create a new class of implants that can sense bone growth, then send that information to an external device. Doctors could monitor the output and determine whether to inject growth hormones or intervene to avoid additional surgery. Right now, implant patients must get an X-ray or undergo a bone scan to monitor bone growth.

Webster claims the biosensing implant concept will work because when cells make calcium, an electrical current is created. That current can be conducted through carbon nanotubes and transmitted via radio frequency to a handheld device outside the body—a similar process to the one employed by state-of-the-art cardiac pacemakers.

“This technology would be incredibly exciting,” explains Webster. “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 [initial] results are a strong first step.”