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7 September 2007
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.
Fig 1
Fig 2
The work was
published in Chemistry of Materials.
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