Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Research brightens prospects for using nature’s smallest candles in medical applications

08.06.2007
In a way, nanotubes are nature’s smallest candles.

These tiny tubes are constructed from carbon atoms and they are so small that it takes about 100,000 laid side-by-side to span the width of a single human hair. In the last five years, scientists have discovered that some individual nanotubes are fluorescent. That is, they glow when they are bathed in light. Some glow brightly. Others glow dimly. Some glow in spots. Others glow all over.

Until now, this property has been largely academic. But researchers from the Vanderbilt Institute of Nanoscale Science and Engineering (VINSE) have removed an obstacle that has restricted fluorescent nanotubes from a variety of medical applications, including anti-cancer treatments. In a paper published online in the Journal of the American Chemical Society on June 7, they describe a method that can successfully produce large batches of highly fluorescent nanotubes.

“Nanotubes have a number of characteristics that make them particularly suitable for use as contrast agents in cells and tissues,” says Tobias Hertel, the associate professor of physics who headed the research. “Now that we know how to separate out the brightest ones, I hope that researchers will begin considering ways to use them in clinical applications.”

The figure of merit for fluorescence is quantum efficiency: the ratio of the number of photons of light that a device emits to the number of photons it absorbs in the process. The VINSE team reports that they can produce populations containing trillions of nanotubes with a quantum efficiency of 1 percent, a factor of 100 better than previous ensemble measurements and close to the best quantum efficiencies reported for individual nanotubes.

The methods researchers use to produce nanotubes creates soot that contains a number of different types of nanotubes: metallic, semiconducting, double-walled, single-walled, etc. Of these, only the single-walled semiconducting nanotubes, or SWNTs, are capable of producing light. Metallic nanotubes actually inhibit the brightness of their fluorescent neighbors. But it has been very difficult to separate the strongly fluorescent SWNTs from all the rest in large quantities.

Nanotube soot is insoluble in water. So researchers routinely mix it with special soap and give it a dose of ultrasound to break apart clumps of nanotubes and force them to dissolve. The result is a dark liquid that is routinely put into an ultracentrifuge that subjects them to forces a few thousand times that of gravity. Centrifuging separates out a number of gross impurities.

Hertel’s team discovered that if they remove the most buoyant layer from the centrifuge, let it set for a while and then put it back in the ultracentrifuge for another 12 hours, the liquid separates into a number of distinct layers. The topmost layer has a purple color and, when analyzed, proves to contain a surprisingly uniform population of the brightest nanotubes.

The researchers had expected this approach to boost the quantum efficiency by five to ten times. The fact that the improvement was considerably larger – 20 to 100 times – came as a pleasant surprise.

“Quantum efficiency is critical, but there are several other factors that make nanotubes particularly well suited for use in living systems,” says Hertel. These factors include:

· Nanotubes emit light in a very narrow range of wavelengths, or colors. This makes it easier to pick out their signal against background noise. Furthermore, they produce light in a part of the spectrum – the near infrared where skin and other tissue is transparent – that allows the nanotube light to stand out.

· Nanotubes are made entirely from graphitic carbon, which is non-toxic and, at least so far, experiments that have been done indicate that they do not damage living cells. By comparison, quantum dots, which are a popular alternative fluorescent tagging technology, contain cadmium, which is highly toxic, and so may not be appropriate for “in vivo” applications.

· Nanotube fluorescence is extremely stable and can last for months. Fluorescent proteins – widely used for imaging living systems – begin fading within a few hours. Quantum dots last several days before degrading.

Hertel’s team is currently working on the next step necessary for many biomedical uses: finding a way to attach molecules to the surface of the nanotubes that will allow them to bind to specific biological targets. The trick is to do so without dimming or extinguishing the nanotubes’ delicate fluorescence.

An example of the possible medical applications of nanotube fluorescence is a collaboration that Hertel and Associate Professor of Biomedical Research Duco Jansen are planning. Jansen has been pursuing research that uses gold nanoclusters to burn away cancer cells. He has developed a selective method for attaching the gold clusters to the surface of tumors and then exposing them to wavelengths of light that cause them to grow hot enough to destroy nearby cells. The approach has one drawback: He doesn’t have an easy way to identify the locations where the clusters attach. Nanotubes should work as well as gold clusters as microscopic blow torches while their fluorescence should make them easy to locate. At least that is the hypothesis the researchers hope to test.

Hertel’s co-authors on the paper are Vanderbilt graduate student Jared Crochet and Michael Clemens, a graduate student from Brigham Young University. The research was funded by grants from the American Chemical Society and the National Science Foundation.

David F. Salisbury | Vanderbilt University
Further information:
http://www.vanderbilt.edu

Further reports about: Efficiency Medical Nanotube Quantum fluorescence fluorescent

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>