Metal Oxide Coating Boosts Bone Healing

A new study suggests that a textured titanium dioxide (TiO2) coating for medical implants could help broken bones and joint replacements heal faster.

Researchers at Ohio State University (OSU; Columbus, USA) developed a simple thermal oxidation process for growing TiO2 nanowires (NWs), each tens of thousands of times thinner than a human hair. The NW growth was modulated by tailoring the mix of materials and gases inside a furnace; at 700 °C, fine filaments of TiO2 rose from the smooth titanium surface. As the NW rose, each one began to wrap a protective coating of aluminum oxide around itself. The researchers stressed that since they were working with pure titanium, it is not clear how the aluminum coating formed.


The researchers then observed in vitro cell adhesion and proliferation of human osteosarcoma (HOS) cells on bare Ti64 and on both nanostructured and non-nanostructured TiO2 surfaces, using fluorescence microscopy and laser scanning cytometry. The alkaline phosphatase (ALP) activity of the HOS cells was also monitored at regular intervals. The researchers found that the NW coated samples showed increased cell adhesion and proliferation, compared to the non-nanostructured TiO2 and Ti64 samples.

The major difference in cell growth occurred within the first 15 hours of testing, when the researchers measured a 20% higher concentration of ALP in the cells growing on the nanowires. By the end of the study, there were around 90,000 cells per cm² on the nanowire surface, an 80% higher density than on the other two surfaces. The study was published in the July 2013 issue of Ceramics International.

“What's really exciting about this technique is that we don't have to carve the nanowires from a solid piece of metal or alloy,” said lead author Professor Sheikh Akbar, PhD, of the department of materials science and engineering. “We can grow them from scratch, by exploiting the physics and chemistry of the materials.”

“Our 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,” added study coauthor Derek Hansford, PhD, an associate professor of biomedical engineering and materials science and engineering. “The coating could aid people who have hip and knee replacements, dental implants, or broken bones that require screws and plates for repair. “A stronger interface means that implants and bones will be better able to share mechanical loads, and we can better preserve healthy bone and soft tissue around the implant site.”

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