"Microscopic shag carpet" may help bones bond with implants

One of the titanium dioxide filaments, that make up the shag carpet coating

Like a lot of things, bone cells grow and reproduce quicker on textured surfaces than on smooth ones. With that in mind, a team of scientists from Ohio State University are developing a new coating that could allow implants such as artificial hips to bond with bones faster. That coating is described as “a microscopic shag carpet made of tiny metal oxide wires.”

The team, led by Prof. Sheikh Akbar, starts by heating a sheet of titanium foil at about 1,300ºF (704ºC) in a furnace. This causes tiny filaments of titanium dioxide to rise from the foil’s surface, each one tens of thousands of times thinner than a human hair. Each filament also grows an outside covering of aluminum oxide, although it’s still not clear why this happens.

In order to test the resulting “nanowire carpet,” the researchers grew bone cancer cells on it, on smooth titanium, and on smooth titanium oxide – bone cancer cells were used because they’re hardy, and reproduce in the same manner as regular bone cells.

Within the first 15 hours, the cells growing on the carpet showed a 20 percent higher concentration of the bone-growth enzyme alkaline phosphatase. Ultimately, 80 percent more cells per square centimeter grew on the carpet, than on either of the other two surfaces.

The process for making the coating is reportedly quite simple and inexpensive, with a US$100 sheet of foil being enough to produce hundreds of pieces. Placed at the interface between bones and implants, it is hoped that the nanowire carpet could be used to quickly create strong bonds between the two. It might also find use in speeding the healing of broken bones.

Scientists at other institutions are also working on bone-to-implant growth coatings that incorporate a bone component known as hydroxyapatite, and “flower bouquet” clusters of an engineered protein.

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