Rice University researchers use spectral triangulation to pinpoint location of tumors
Bathing a patient in LED light may someday offer a new way to locate tumors, according to Rice University researchers.
A new Rice University method for medical imaging uses strong light from an LED array and an avalanche photodiode detector to pinpoint the location of tumors that have been tagged by antibody-targeted carbon nanotubes. The method can detect fluorescence from single-walled carbon nanotubes (SWCNTs) through up to 20 millimeters of tissue.
Credit: Weisman Lab/Rice University
The spectral triangulation system developed by Rice chemist Bruce Weisman and his colleagues is intended to pinpoint targeted cancer tumors tagged with antibody-linked carbon nanotubes. It is described in a paper in the Royal Society of Chemistry journal Nanoscale.
Because the absorption of short-wave infrared light in tissues varies with its wavelength, spectral analysis of light coming through the skin can reveal the depth of tissue through which that light has passed. This allows the three-dimensional coordinates of the nanotube beacon to be deduced from a small set of noninvasive optical measurements.
The Rice technique relies on the fact that single-walled carbon nanotubes naturally fluoresce at short-wave infrared wavelengths when excited by visible light. A highly sensitive detector called an InGaAs (indium gallium arsenide) avalanche photodiode made it possible to read faint signals from nanotubes up to 20 millimeters deep in the simulated tissue used for lab tests.
"We're using an unusually sensitive detector that hasn't been applied to this sort of work before," said Weisman, a recognized pioneer for his discovery and interpretation of near-infrared fluorescence from single-walled nanotubes.
"This avalanche photodiode can count photons in the short-wave infrared, which is a challenging spectral range for light sensors. The main goal is to see how well we can detect and localize emission from very small concentrations of nanotubes inside biological tissues. This has potential applications in medical diagnosis."
Using light-emitting diodes to excite the nanotubes is effective -- and inexpensive, Weisman said. "It's relatively unconventional to use LEDs," he said. "Instead, lasers are commonly used for excitation, but laser beams can't be focused inside tissues because of scattering. We bathe the surface of the specimen in unfocused LED light, which diffuses through the tissues and excites nanotubes inside."
A small optical probe mounted on the frame of a 3-D printer follows a computer-programmed pattern as the probe gently touches the skin to make readings at grid points spaced a few millimeters apart.
Before reaching the detector, light from the nanotubes is partly absorbed by water as it travels through tissues. Weisman and his team use that to their advantage. "A two-dimensional search tells us the emitter's X and Y coordinates but not Z -- the depth," he said. "That's a very difficult thing to deduce from a surface scan."
Spectral triangulation overcomes the limitation. "We make use of the fact that different wavelengths of nanotube emission are absorbed differently going through tissue," Weisman said. "Water (in the surrounding tissue) absorbs the longer wavelengths coming from nanotubes much more strongly than it does the shorter wavelengths.
"If we're detecting nanotubes close to the surface, the long and the short wavelength emissions are relatively similar in intensity. We say the spectrum is unperturbed.
"But if the emission source is deeper, water in that tissue absorbs the longer wavelengths preferentially to the shorter wavelengths," he said. "So the balance between the intensities of the short and long wavelengths is a yardstick to measure how deep the source is. That's how we get the Z coordinate."
The detector is now being tested in the lab of Dr. Robert Bast, an expert in ovarian cancer and vice president for translational research at the University of Texas MD Anderson Cancer Center.
"It gives us a fighting chance to see nanotubes deeper inside tissues because so little of the light that nanotubes emit finds its way to the surface," Weisman said. "We've been able to detect deeper into the tissues than I think anyone else has reported."
Rice graduate student Ching-Wei Lin is lead author of the paper. Rice research scientist Sergei Bachilo, postdoctoral fellow Michael Vu and Kathleen Beckingham, a professor of biochemistry and cell biology, are co-authors.
The National Science Foundation, the Welch Foundation, the National Institutes of Health and the John S. Dunn Foundation Collaborative Research Award Program supported the research.
Read the abstract at http://pubs.
This news release can be found online at http://news.
Follow Rice News and Media Relations via Twitter @RiceUNews
Bruce Weisman: https:/
Wiess School of Natural Sciences: http://natsci.
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.
David Ruth | EurekAlert!
TSRI researchers develop new method to 'fingerprint' HIV
29.03.2017 | Scripps Research Institute
Periodic ventilation keeps more pollen out than tilted-open windows
29.03.2017 | Technische Universität München
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences