Sep 7, 2007
Medical implants benefit from nanowire coating
A simple and inexpensive way to create a nanowire coating on the surface of biocompatible titanium has been developed by researchers at the University of Arkansas in the US. The technique could be used to create more effective surfaces for prosthetics, such as hip replacements, as well as in dental reconstruction and vascular stents. The material can also be easily sterilised using ultraviolet light and water or ethanol, which means it could safely be used in hospitals.
Titanium implants are widely used in reconstructive bone surgery, such as hip replacements. The trouble is that muscle tissue may not adhere very well to titanium's smooth surface. This causes the implant to fail after just a decade or so and means that the patient must undergo surgery again.
Now, Wenjun Dong and colleagues have found that coating the implant with titanium oxide nanowires beforehand could help overcome this problem. Indeed, the researchers have found that tissue adheres to a joint containing the nanowire coating after just four week in experiments on mice (figure 1).
Dong and colleagues began by heating together a clean titanium substrate with sodium hydroxide solution at 160 to 250 °C for 2 to 10 h. This lead to the production of macroporous titanium oxide nanowire scaffolds that completely covered the substrate.
The researchers say that they can control the length, height and pore openings and volumes within the nanowire scaffolds by varying the temperature and the concentration of alkali in the reaction (figure 2). This means that the material could also be coated onto stents in patients with coronary artery disease. Conventional stents can sometimes become reclogged with fat after they are implanted but the nanowire coating could be exploited to carry drugs that would help keep arteries clog-free for long periods.
And that's not all: the nanofibre scaffold can be sterilised by simply rinsing it in water and exposing it to UV light, which kills more than 99% of bacteria on its surface. An alternative methods is to soak the material in 70 % ethanol, which completely sterilises the material. Both techniques mean that the nanowire coating could safely be employed in hospitals in the future, say the scientists.
The team has applied for a provisional patent for the multifunctional nanowire scaffolds on titanium or titanium-containing alloys.
The work was published in Chemistry of Materials.