Navigation Links
Better viewing through fluorescent nanotubes when peering into innards of a mouse
Date:5/27/2011

Developing drugs to combat or cure human disease often involves a phase of testing with mice, so being able to peer clearly into a living mouse's innards has real value.

But with the fluorescent dyes currently used to image the interior of laboratory mice, the view becomes so murky several millimeters under the skin that researchers might have more success divining the future from the rodent's entrails than they do extracting usable data.

Now Stanford researchers have developed an improved imaging method using fluorescent carbon nanotubes that allows them to see centimeters deep into a mouse with far more clarity than conventional dyes provide. For a creature the size of a mouse, a few centimeters makes a great difference.

"We have already used similar carbon nanotubes to deliver drugs to treat cancer in laboratory testing in mice, but you would like to know where your delivery went, right?" said Hongjie Dai, a professor of chemistry. "With the fluorescent nanotubes, we can do drug delivery and imaging simultaneously in real time to evaluate the accuracy of a drug in hitting its target."

Researchers inject the single-walled carbon nanotubes into a mouse and can watch as the tubes are delivered to internal organs by the bloodstream.

The nanotubes fluoresce brightly in response to the light of a laser directed at the mouse, while a camera attuned to the nanotubes' near infrared wavelengths records the images.

By attaching the nanotubes to a medication, researchers can see how the drug is progressing through the mouse's body.

Dai is the one of the authors of a paper describing the research published online this month in Proceedings of the National Academy of Sciences.

The key to the nanotubes' usefulness is that they shine in a different portion of the near infrared spectrum than most dyes.

Biological tissues whether mouse or human naturally fluoresce at wavelengths below 900 nanometers, which is in the same range as the available biocompatible organic fluorescent dyes. That results in undesirable background fluorescence, which muddles the images when dyes are used. But the nanotubes used by Dai's group fluoresce at wavelengths between 1,000 and 1,400 nanometers. At those wavelengths there is barely any natural tissue fluorescence, so background "noise" is minimal.

The nanotubes usefulness is further boosted because tissue scatters less light in the longer wavelength region of the near-infrared, reducing image smearing as light moves or travels through the body, another advantage over fluorophores emitting below 900nm.

"The nanotubes fluoresce naturally, but they emit in a very oddball region," Dai said. "There are not many things living or inert that emit in this region, which is why it has not been explored very much for biological imaging."

By selecting single-walled carbon nanotubes (SWNTS) with different chiralities diameters and other properties, Dai and his team can fine-tune the wavelength at which the nanotubes fluoresce.

The nanotubes are imaged immediately upon injection into the bloodstream of mice.

Dai and graduate students Sarah Sherlock and Kevin Welsher, who are also coauthors of the PNAS paper, observed the fluorescent nanotubes passing through the lungs and kidneys within seconds after injection. The spleen and liver lit up a few seconds later.

The group also did some "post-production" work on digital video footage of the circulating nanotubes to further enhance the image quality using a process called "principal component analysis."

"In the raw imaging, the spleen, pancreas and kidney might appear as one generalized signal," Sherlock said. "But this process picks up the subtleties in signal variation and resolves what at first appears to be one signal into the distinct organs."

"You can really see things that are deep inside or blocked by other organs such as the pancreas," Dai said.

There are some other imaging methods that can produce deep tissue images, such as magnetic resonance imaging (MRI) and computer tomography (CT) scans. But fluorescence imaging is widely used in research and requires simpler machinery.

Dai said that the fluorescent nanotubes are not capable of reaching the depth of CT or MRI scans, but nanotubes are a step forward in broadening the potential uses of fluorescence as an imaging system beyond the surface and near-surface applications it has been restricted to up until now.

Since nanotube fluorescence was discovered about ten years ago, researchers have been trying to make the fluorescence brighter, Dai said. Still, he has been a little surprised at just how well they now work in animals.

"I did not imagine they could really be used in animals to get deep images like these," he said. "When you look at images like this, you get a sense that the body almost has some transparency to it."


'/>"/>

Contact: Louis Bergeron
louisb3@stanford.edu
650-725-1944
Stanford University
Source:Eurekalert  

Related biology news :

1. Better buildings for extreme climates will be focus of researchers talk
2. Reforestation research in Latin America helps build better forests
3. Californias draft Bay Delta conservation plan incomplete; needs better integration to be more scientifically credible
4. Damaged hearts pump better when fueled with fats
5. Physical and emotional health of older couples linked for better or worse, study finds
6. Food safety in Canada is lax and needs better oversight, says CMAJ
7. People control thoughts better when they see their brain activity: UBC study
8. Science 101: Different teaching fosters better comprehension
9. A better understanding of the aging immune system
10. Getting closer to a better biocontrol for garden pests
11. In the race of life, better an adaptable tortoise than a fit hare
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Better viewing through fluorescent nanotubes when peering into innards of a mouse 
(Date:11/17/2016)... , Nov. 17, 2016  AIC announces that it has just released a new ... that require high-performance scale-out plus high speed data transfer storage solutions. Photo ... ... ... Setting up a high performance computing ...
(Date:11/15/2016)... Nov 15, 2016 Research and Markets has ... to 2021" report to their offering. ... ... Billion by 2021 from USD 6.21 Billion in 2016, growing at ... Growth of the bioinformatics market is driven by the growing demand ...
(Date:6/27/2016)... 27, 2016 Research and Markets has announced ... report to their offering. ... to grow at a CAGR of 12.28% during the ... on an in-depth market analysis with inputs from industry experts. The ... coming years. The report also includes a discussion of the key ...
Breaking Biology News(10 mins):
(Date:12/5/2016)... ... December 05, 2016 , ... In anticipation of ... lumbar disc production, company President, Jake Lubinski will be traveling to Germany on ... disc in Cologne and Karlsruhe to discuss the benefits of a viscoelastic total ...
(Date:12/5/2016)... WOODCLIFF LAKE, N.J. , Dec. 5, 2016 ... its Phase 3 open-label two-year study of rufinamide, ... of the American Epilepsy Society (AES) held from ... . Analysis of final two-year safety, tolerability and ... therapy with rufinamide experienced similar safety and tolerability ...
(Date:12/4/2016)... DIEGO , Dec. 3, 2016  In five ... of Hematology (ASH) Annual Meeting and Exposition in ... biomedical engineering methods to improve the delivery of life-saving ... These new methods are designed to carry therapies directly ... needed most, which could provide a substantial advantage over ...
(Date:12/2/2016)... Amgen (NASDAQ: AMGN ) and Allergan ... of a Marketing Authorization Application (MAA) to the European Medicines ... ® (bevacizumab). The companies believe this submission is the ... "The submission of ABP 215 to the EMA is ... portfolio," said Sean E. Harper , M.D., executive vice ...
Breaking Biology Technology: