Originally Published MDDI December 2002
R&D DIGEST
Self-Generating Nanotubes Provide "Dial-Up" Properties
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| By manipulating the chirality of the material, researchers can control the direction in which the spiral-shaped nanotubes twist. (click to enlarge) |
Nanotubes have clearly come to be viewed as one of the more promising enabling technologies for advancing medical capabilities over the long term. Potential applications range from new methods of disease treatment to innovative plastics manufacturing techniques.
A Purdue University (West Lafeyette, IN) research team led by Hicham Fenniri, PhD, assistant professor of supramolecular chemistry, announced that it has identified a method for creating multiple "species" of nanotubes that possess unprecedented physical and chemical properties. They add that each species could lead to a different application.
The group also says they have developed a method for exerting control over the nanotubes' formation. This capability enables the team to virtually "dial up" the properties they wish their nanotubes to possess. The findings could expand the range of materials available for use on the nanoscale, according to the researchers.
Says Fenniri, "Instead of being limited to building blocks of one size, shape, and color, it's as though we now have a brickyard with many different varieties. This research could give a nanotechnologist a lot more materials for construction."
Part of the innovative approach taken by the Fenniri team has been to form the nanotubes from synthetic organic molecules. "By using synthetic chemistry, we have gained complete control over the formation of our nanotubes," Fenniri explains. "More control in the lab should give more options to industry."
One way the new nanotubes can be customized is by using them as scaffolding for other materials. The Purdue team's nanotubes look like spiral-shaped stacks of rings; each ring is made of six molecules shaped roughly like pie wedges. On the outside of the spiral, the team attaches other molecules, which hang off the tubes like charms on a charm bracelet. The attached molecules then lend their properties to the outside of the nanotube.
The group has also determined how to manipulate the chirality of the material. This allows the direction in which the spiral-shaped tubes twist to be controlled. The group explains that nature only twists molecules in one direction. The new technique, however, allows tubes to be made that twist in either direction. The result is that "left-handed" nanotubes can be created that have abilities not exhibited by the right-handed versions.
The team also identified some unexpected behaviors displayed by the custom nanotubes—such as self-generation. Says Fenniri, "We have found that the nanotubes promote their own formation. Such behavior is very reminiscent of living systems, in that they replicate and adapt to their environment."
They also found that by placing the raw materials from which nanotubes form into a test tube and adjusting such conditions as temperature and pressure, the nanotubes could organize themselves into one of many different configurations. Some of the formations that occurred had not been seen previously.
The relative ease of manipulating the properties of nanotubes makes Fenniri optimistic that many new applications will be possible. One possibility is to use the nanotubes in disease treatment. "Many drugs destroy infectious bacteria by poking holes in their cellular membranes and allowing their nutrients to leak out, just like pricking a hole in a balloon," he says. "Our nanotubes could also act in this manner, but in addition, they have the ability to lure the bacteria with a bait that guides them to the cell membrane where they can start destroying the cell."
Further research on the tubes' dial-up properties could lead to development of biosensors and drug-delivery systems. Says Fenniri, "Nanotechnology relies on our ability to control the behavior of matter at the molecular scale." He adds, "The versatility and robustness of our system is already pointing the way towards numerous applications in a fairly broad range of disciplines. It should help nanotubes on their way to becoming the nanoworld's jack-of-all-trades."
Copyright ©2002 Medical Device & Diagnostic Industry
