Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

3-D imaging inside living organism, using quantum dots coursing through mouse’s body, reported by Cornell researchers

30.05.2003


The branched capillary structure, feeding adipose tissue in a living mouse, is revealed with multiphoton fluorescence microscopy as nanocrystal quantum dots circulate through the bloodstream. Credit: Bioimaging Resource/Cornell University

Copyright © Cornell University


Multiphoton fluorescence microscopy with quantum dots illuminates a capillary beneath the skin of a living mouse. In this image, collagen is imaged in blue by second harmonic generation while quantum dots inside the capillary are imaged in yellow by two-photon fluorescence excitation. Because red blood cells exlude the quantum dots, they appear as shadows within the capillaries, which can be monitored over time (yellow trace at bottom of image). Credit: Bioimaging Resource/Cornell University. Copyright © Cornell University


Tiny blood vessels, viewed beneath a mouse’s skin with a newly developed application of multiphoton microscopy, appear so bright and vivid in high-resolution images that researchers can see the vessel walls ripple with each heartbeat -- 640 times a minute.

The capillaries are illuminated in unprecedented detail using fluorescence imaging labels, which are molecule-size nanocrystals called quantum dots circulating through the bloodstream. Quantum dots are microscopic metal or semiconductor boxes (in this case cadmium selenide-zinc sulfide) that hold a certain number of electrons and, thus, have a wide number of potential applications in electronics and photonics.

Writing in the latest issue of the journal Science (May 30, 2003), researchers at Cornell University and a nanocrystal manufacturer, Quantum Dot Corp., report that the nanocrystals are particularly useful for producing high-resolution, three-dimensional images inside living.



"We have demonstrated a new approach to using quantum dots for biological studies of living animals," says Watt W. Webb, Cornell’s S.B. Eckert Professor of Engineering and professor of applied physics, co-inventor of multiphoton microscopy (with Winfried Denk) and leader of the experimental imaging team at Cornell.

"Of course, there are easier ways to take a mouse’s pulse," says Webb’s Cornell collaborator, senior research associate Warren R. Zipfel, "but this kind of resolution and high signal-to-noise illustrates how useful multiphoton microscopy with quantum dots can become, in a biological research context, for tracking cells and visualizing tissue structures deep inside living animals."

Zipfel cited the study of vascular changes in cancer tumors as one possible application, cautioning that the Cornell researchers are not ready to recommend human-medicine clinical applications for quantum dot imaging, in part because some of the best fluorescing nanocrystals have unknown toxicity. However, mice used in the Cornell study are still alive and apparently healthy, months later, and are being monitored for long-term effects of their treatments.The Cornell researchers used quantum dots for fluorescence imaging microscopy because when excited by light, they emit bright fluorescence in different colors, according to their size, reports biophysics graduate student Daniel Larson. The quantum dots were 6 to 10 nanometers in diameter. (A nanometer is one one-billionth of a meter. By comparison, a red blood cell, at 7 millionths of a meter, is a thousand times bigger). "Even with their water-soluble coating, which is something like being encased in a soap bubble, the quantum dots are only about 24 nanometers in diameter," Larson notes.

Webb explains that the laser scanning microscope used in multiphoton microscopy is particularly adept at producing high-resolution, three-dimensional images inside living tissue because it combines the energies of two photons, striking a molecule at the same time, with an additive effect. Under the conditions used, this only occurs at the focus of the laser, so only at that point is the molecule excited to a state that results in fluorescence emission. This excitation is the same as if it arose from the absorption of a single photon of higher energy, but it is three-dimensionally localized since it is only occurring at the beam focus. The scanning microscope moves the laser beam across the area being imaged at a precise depth. When repeated scans at different planes of focus are "stacked," the result is a brightly lit and vividly detailed three-dimensional image -- and video that takes a viewer inside a living organism..

Because of the special properties of the nanoparticles, multiphoton microscopy with quantum-dot imaging can be 1,000 times brighter in tissue than conventional organic fluorophores (the chemical labels that are temporarily added to samples), says Webb. "We looked to quantum dots for even brighter images at better resolution, and that’s what we found."

Results presented in the Science report show highly detailed images of capillaries beneath the skin of a living mouse after quantum dots were injected through a vein in its tail, as well as capillaries through the adipose (fat) layer around the mouse’s ovaries. The researchers were particularly surprised at the saw-toothed ripples in the walls of one capillary image -- until they made a calculation. Noting the time it took to scan that part of the tiny blood vessel and the animal’s heart rate during the experiment, they determined that each ripple represented the undulation of the capillary wall from one heartbeat.

Besides demonstrating the feasibility of microscopic angiography with quantum-dot labeling through skin and adipose tissue -- two of the most challenging tissue types -- the researchers said they had resolved several fundamental questions, including the fact that sometimes as many as half the dots in a preparation are not fluorescent.

Other authors of the Science article are Marcel P. Bruchez, principal scientist at Quantum Dots; Rebecca M. Williams, a research associate with the National Institutes of Health (NIH)-funded Bioimaging Resource at Cornell; Frank Wise, professor of applied and engineering physics; and Stephen W. Clark, a graduate student in Wise’s laboratory. Funding came from NIH, the Defense Advanced Research Projects Agency and the National Science Foundation.

Roger Segelken | Cornell News
Further information:
http://www.news.cornell.edu/releases/May03/quantum_dots.hrs.html

More articles from Interdisciplinary Research:

nachricht A new method for the 3-D printing of living tissues
16.08.2017 | University of Oxford

nachricht Bergamotene - alluring and lethal for Manduca sexta
21.04.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Interdisciplinary Research >>>

The most recent press releases about innovation >>>

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

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Glycosylation: Mapping Uncharted Territory

21.09.2017 | Life Sciences

Highly precise wiring in the Cerebral Cortex

21.09.2017 | Health and Medicine

Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?

21.09.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>