“Since bone itself possesses numerous nanometre bumps, it seemed reasonable that cells are accustomed to such surface roughness and would have better responses on such materials,” Tom Webster told nanotechweb.org. “We decided to pursue metal nanobumps since metals are the primary materials used for orthopaedic implants. The orthopaedic materials currently used fail on average after 15 years.”

Webster and colleague Jeremiah Ejiofor tested both nanophase and conventional samples of titanium, titanium-aluminium-vanadium alloy and cobalt-chromium-molybdenum alloy. The scientists made up the test samples by powder metallurgy from different-sized particles of the materials. The team used compression but no heat to compact the samples - this avoided changes in surface chemistry so that the only difference between the conventional and nanophase samples was the surface roughness.

For all three materials, osteoblasts adhered better to the rougher surface of the nanophase version than the conventional sample. For example, about 2300 out of 2500 bone cells in suspension adhered to the nanophase titanium alloy after three hours, compared with about 1300 cells adhering to the conventional alloy.

“The most significant application is the use of these materials as coatings for traditional orthopaedic implant materials,” said Webster. “These nanophase coatings would be bioactive and would result in increased bone tissue formation to bond to existing bone for firm fixation, so that the patient can return to a normal active lifestyle. In addition, the new bonding would hopefully be firm enough so that the patient would never need a revision surgery.”

The researchers reported their work at the Nanoparticles 2003 conference in Boston, US.