Nav: Home

Nanotubes are beacons in cancer-imaging technique

May 20, 2016

Bathing a patient in LED light may someday offer a new way to locate tumors, according to Rice University researchers.

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."
-end-
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.rsc.org/en/content/articlelanding/2016/nr/c6nr01376g#!divAbstract

This news release can be found online at http://news.rice.edu/2016/05/20/nanotubes-are-beacons-in-cancer-imaging-technique/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Bruce Weisman: https://chemistry.rice.edu/FacultyDetail.aspx?RiceID=597

Wiess School of Natural Sciences: http://natsci.rice.edu

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.com/RiceUniversityoverview.

Rice University

Related Nanotubes Articles:

Why modified carbon nanotubes can help the reproducibility problem
Scientists at Tokyo Institute of Technology (Tokyo Tech) conducted an in-depth study on how carbon nanotubes with oxygen-containing groups can be used to greatly enhance the performance of perovskite solar cells.
Watching energy transport through biomimetic nanotubes
Scientists from the University of Groningen (the Netherlands) and the University of Würzburg (Germany) have investigated a simple biomimetic light-harvesting system using advanced spectroscopy combined with a microfluidic platform.
Neural networks will help manufacture carbon nanotubes
A team of scientists from Skoltech's Laboratory of Nanomaterials proposed a neural-network-based method for monitoring the growth of carbon nanotubes, preparing the ground for a new generation of sophisticated electronic devices.
Photovoltaic nanotubes
Physicists discovered a novel kind of nanotube that generates current in the presence of light.
Chemical synthesis of nanotubes
For the first time, researchers used benzene -- a common hydrocarbon -- to create a novel kind of molecular nanotube, which could lead to new nanocarbon-based semiconductor applications.
Nanotubes may give the world better batteries
Rice University scientists use thin films of multiwalled carbon nanotubes to keep lithium metal from sprouting dendrites, tentacle-like growths that can cause batteries to fail.
Deformation of nanotubes to control conductivity
Scientists from the NUST MISIS Laboratory of Inorganic Nanomaterials together with their international colleagues have proved it possible to change the structural and conductive properties of nanotubes by stretching them.
Nanotubes change the shape of water
Nanotubes of the right diameter can prompt water inside to solidify into a square tube, transitioning into a kind of ice.
Touchy nanotubes work better when clean
Heating carbon nanotubes at high temperatures and slowly cooling them eliminates contaminants that make nanotubes difficult to test for conductivity.
Carbon nanotubes devices may have a limit to how 'nano' they can be
Carbon nanotubes bound for electronics not only need to be as clean as possible to maximize their utility in next-generation nanoscale devices, but contact effects may limit how small a nano device can be, according to researchers at the Energy Safety Research Institute (ESRI) at Swansea University in collaboration with researchers at Rice University.
More Nanotubes News and Nanotubes Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.