Engineers at The Ohio State University, Columbus, discovered that bone cells grow and reproduce faster on a textured surface than on a smooth one—and grow best when they can cling to a microscopic "shag carpet" made of tiny metal oxide wires. The discovery could someday help broken bones and joint replacements heal faster, they say.
In studies, the wires boosted cell growth by nearly 80 percent compared to other surfaces, which suggests that the coating would help healthy bone form a strong bond with an implant faster.
The engineers developed an affordable technique for creating the wires, saying that they can grow them from scratch by tailoring a mix of materials and gases inside a furnace. At around 1,300°F, fine filaments of titanium dioxide rose from a smooth titanium surface. Each was tens of thousands of times smaller than a human hair.
But then, strangely, each wire grew a protective coating of aluminum oxide around itself, like a layer of bark around a tree trunk. The growth of the coating might make sense, if the material in the furnace were a titanium alloy that contained aluminum. But in this case, the researchers were working with pure titanium, so they're not certain how the wires grew an aluminum coating.
In tests, the researchers grew bone cancer cells on three different surfaces: smooth titanium, smooth titanium dioxide, and the nanowire carpet. The biggest difference in cell growth occurred within the first 15 hours of testing, when researchers measured a 20 percent higher concentration of the bone-growth enzyme alkaline phosphatase being produced by the cells growing on the nanowires. By the end of the study, there were around 90,000 cells per square centimeter on the nanowire surface—80 percent more than the 50,000 cells per square centimeter on each of the other two surfaces.
They say that their hope is that this surface treatment will become a simple-to-implement modification to titanium implants to help them form a stronger interface with surrounding bone tissue. They also say that the price is right for commercial development, as about $100 worth of metal foil is enough to make hundreds of samples.
