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Science, Medicine, Technology
 
 
  David J. Brenner, a radiation oncology professor, is leading an effort to develop minimally invasive radiation screening techniques.
 
Preparing for the unthinkable

The nightmare is all too plausible: a terrorist detonates a dirty bomb in a city and in the ensuing panic hospitals become overwhelmed, unable to identify quickly those patients who need treatment for radiation exposure.

To ensure that a large population could be tested quickly for exposure, the National Institutes of Health recently awarded a $25 million five-year grant to a nine-institution research consortium led by Columbia University to develop screening tools that are highly automated and minimally invasive.

Current radiation screening technology is not automated and therefore slow and cumbersome, says principal investigator David J. Brenner. If a dirty bomb packed with radioactive material were detonated in a city, he says, it is likely that everybody within at least a few blocks of the explosion would need to be screened, depending on the size of the explosive device and the potency of the radioactive material. Screening would need to take place within days, if not hours.

In addition to identifying people needing treatment, medical professionals would need to be able “to reassure people who are OK by screening them,” says Brenner, a professor of radiation oncology at the College of Physicians and Surgeons and a professor of public health at the Mailman School of Public Health. “Otherwise, every hospital will be overwhelmed.”

The researchers are developing three potential screening methods. The most promising, but most invasive, Brenner says, would entail taking a pinprick of blood from the finger and, with the help of a superfast, high-resolution microscope currently being developed by mechanical engineers at Columbia, analyzing cells for structural damage that indicates radiation exposure. Because the goal is to develop an apparatus that could test as many as 30,000 patients in a day, the entire process must be completely automated, even the pinprick, which could be executed by lasers. Brenner expects that a prototype device will be ready for market within three to four years.

The second method, which is more speculative, involves analyzing blood samples for changes to DNA that indicate radiation exposure. A third method, also speculative, would analyze sweat, saliva, or urine instead of blood, making the process less invasive and easier to administer. However, Brenner says it will take three to four years for scientists to determine if saliva is a viable medium.

An interdisciplinary team of Columbia radiological researchers and mechanical engineers is developing the technologies. Sally A. Amundson, an associate professor of radiation oncology, is the study’s coprincipal investigator. The mechanical engineering team will be led by Lawrence Yao, chair of mechanical engineering, and Nabil Simaan, an assistant professor of mechanical engineering and an expert in medical robotics.

As part of the grant, the New York City Department of Health and Mental Hygiene plans to research the logistics of administering the screening tests in local neighborhoods.

Other members of the consortium include Harvard University’s School of Public Health; Arizona State University’s Biodesign Institute; the National Cancer Institute; University of Pittsburgh Medical Center; Charles University, Prague; Translational Genomics Research Institute; and Sionex Corporation.
 


 
  Prenatal air

Researchers at the Columbia Center for Children’s Environmental Health (CCCEH) have found that when women are exposed to high levels of air pollution while pregnant, their unborn babies are at risk for cognitive problems early in life. Previous research at CCCEH showed that prenatal exposure to the polycyclic aromatic hydrocarbons (PAHs) in automobile exhaust and in most other types of smoke can stunt a fetus’s physical growth. The new study, published online April 24 in Environmental Health Perspectives, is the first to link the common air pollutants to delays in mental development.

Lead author Frederica Perera and her colleagues conducted cognitive tests on 183 3-year-old children of nonsmoking African American and Dominican women in the New York City neighborhoods of Washington Heights, Central Harlem, and the South Bronx. While pregnant the women carried backpack monitors that measured their exposure to PAHs. Children whose mothers were exposed to the highest levels of pollutants were almost three times as likely to show developmental delays than children with less prenatal exposure. The researchers controlled for exposure to tobacco smoke, lead, and other environmental contaminants, as well as for socioeconomic factors.

“These findings are of concern because compromised mental performance in the preschool years is an important precursor to subsequent educational performance deficits,” says Perera, CCCEH’s director and a professor of environmental health sciences at the Mailman School of Public Health.

Perera’s research team has referred the developmentally delayed children to early intervention remedial services; CCCEH also provides educational resources to local women about how to minimize their exposure to air pollutants. Levels of airborne contaminants tend to be disproportionately high in poor areas such as northern Manhattan and the South Bronx due to heavily trafficked roadways and large numbers of bus depots and sewage waste treatment plants. For this reason, CCCEH encourages area residents to join community activist organizations such as West Harlem Environmental Action and the South Bronx Clean Air Coalition, which have been successful in pressing the city to decrease harmful emissions from its diesel bus fleet.

“Fortunately, airborne PAH concentrations can be reduced by currently available pollution controls, greater energy efficiency, and the use of alternative energy sources,” Perera says. CCCEH plans to follow its young research subjects through adolescence to understand the long-term effects of prenatal exposure to air pollution.

To learn more about the center, visit ccceh.org.
 


 
 
  This rendering shows a split carbon nanotube linked by a single molecule.
See you, silicon

Columbia researchers achieved major breakthroughs recently in developing tiny cylindrical pieces of carbon, known as nanotubes, as electronic circuits, which could have applications for building faster and smaller computers and also for creating new environmental sensors. Carbon nanotubes are elongated organic threads much smaller than the silicon transistors in today’s computer chips, and yet they are extremely strong and pliable. Most importantly, some nanotubes are natural semiconductors, so they can be made to act as transistors, that is, tiny switches that turn on and off the flow of electric current.

Back in January, Colin Nuckolls ’98GSAS, an associate professor of organic chemistry, coauthored a paper in Science that demonstrated how carbon nanotubes could link in stable arrangements to single organic molecules. The resulting molecular bridge could operate as an electronic switch when its pH is altered by adding a proton to it. Scientists and engineers working in this area of nanotechnology previously had been unable to achieve stable electronic connections between carbon nanotubes and other molecules. Nuckolls’s research team used a lithographic technique called oxidative cutting to slice open a nanotube, whose ends were the same size as a single organic molecule and proved chemically receptive to it.

And in a forthcoming article in the Proceedings of the National Academy of Sciences, Nuckolls’s research team describes how a similarly constructed transistor can sense and respond to its chemical environment. New types of molecular sensors based on the technology could be used to detect cancer cells in the body, for example, or identify biotoxins in the atmosphere.

“Molecular electronics has real-world relevance,” says Nuckolls. “It opens the door to new types of ultrasmall switches and sensors. We are able to form a bridge, both literally and figuratively, by combining reaction chemistry with ultrafine lithography.”

Nuckolls’s collaborators include Philip Kim, an assistant professor of physics, and Jim Hone, an assistant professor of mechanical engineering.

 

 
 
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