The researchers used an alkali and heat to create titanium oxide-based
ceramic nanowires that coat the surface of a titanium medical device.
"We can control the length, the height, the pore openings and the pore
volumes within the nanowire scaffolds" by varying the time,
temperature and alkali concentration in the reaction, said Z. Ryan
Tian, assistant professor of chemistry and biochemistry in the J.
William Fulbright College of Arts and Sciences. "This process is also
extremely sustainable," requiring only that the device be rinsed in
reusable water after the heating process.
Reconstructive bone surgeries, such as hip replacements, use titanium
implants. However, muscle tissue may not adhere well to titanium's
smooth surface, causing the implant to fail after a decade or so and
requiring the patient to undergo a second surgery.
Tian and his colleagues created a nanowire-coated joint and placed it
in mice. After four weeks, the researchers found that tissue had
adhered to the joint.
"We saw beautiful tissue growth - lots of muscle fibers," Tian said. "We've
added one more function to the currently-in-use titanium implant."
Because the researchers can control the size and shape of the pores in
the nanowire scaffold, the material also could be coated onto stents
used in patients with coronary artery disease and in potential stroke
victims. Conventional stents sometimes become reclogged with fat after
implantation. The most recent stent used to address this problem,
called the drug-eluting stent, consists of a polymer coating mixed
with the drugs, but the coating may be vulnerable to biodegradation,
and may not function for long. The nanowire coating without the
degradation problem could be used to carry drugs that would help keep
the arteries clear over a long period of time.
"This drug release could be applied to the angioplasty catheter's
surface," Tian said.
In addition to these biomedical applications, the nanofiber scaffold
has a property that may make it useful in both hospitals and food
processing plants: The material, when rinsed in water and exposed to
ultraviolet light, kills more than 99 percent of bacteria on its
surface. This effect occurs because photons from the light cause a
charge separation on the material, splitting water molecules into free
radicals that destroy the bacteria. Alternatively, immersion in 70
percent ethanol completely sterilizes the material, allowing growth of
cells/tissues in the laboratory prior to implantation.
This property could prove extremely useful in bacteria-prone
environments, performing such functions as sterilizing on-site surgery
hospitals used during military actions or cleaning surfaces in
meat-processing plants.
"You could just use water to rinse and UV light to sterilize surfaces,"
Tian said.
The researchers have applied for a provisional patent for the
multifunctional nanowire bioscaffolds on titanium or
titanium-containing alloys such as Nitinol.
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