Linda Powers: Detecting and capturing microbes

Devices that spin off from the research of a University of Arizona (UA) bioengineer may one day protect airports and border checkpoints, enhance the work of pharmaceutical companies and speed the tests of water quality around the world.

On a battlefield, her instant blood test for HIV and hepatitis could hasten a direct transfusion and save a soldier's life. Her device to test for signs of life in extreme environments like outer space could help NASA search for extraterrestrial life.

Linda Powers, a UA bioengineer and BIO5 member, has done such projects and many more in the field of medical diagnostics. Her tools may help the world cope with SARS, bird flu and anthrax, threats that will need super-fast field tests for hazardous microbes, or pathogens.

Powers, who is the Thomas R. Brown Chair in Bioengineering and has an appointment in the Electrical and Computer Engineering Department, organizes branches of her research at three major labs scattered around the campus including BIO5's Thomas W. Keating Bioresearch Building.

'The UA,' she says, 'is perfect for interdisciplinary work. There are no 'glass' walls like you might find at so many places.'

Her work is unfolding on the frontiers where biology, medicine and engineering converge. Her techniques involve intricate ways to capture molecules, those belonging to pathogens or other biochemicals, and then use them in a broad range of nanoscience devices to instantly rule in or out the presence of similar molecules.

The military applications are clearly the most compelling.

'Imagine a soldier is dying, and a buddy says, 'Take my blood and save my buddy,' ' Powers said. 'Now you can make that decision within minutes. That's just one example of why we are so interested in using this technology.'

In the case of blood testing, results with the old methods can take 24 to 48 hours or longer, especially if separate tests are done for the 15 or 20 common blood-borne threats like HIV or hepatitis B.

'There are some microbes that are not pathogenic, some that are. Checking on all the possibilities can require a battery of different tests,' Powers said. 'It would be cumbersome outside a lab, a huge screening process.'

Powers, who has a Harvard doctorate in biophysics, has helped scientists start small businesses like her own venture, MicroBioSystems, a company that is now based in Utah, but which will soon be making Tucson its home.
Her company's mission reflects some parallels with the spirit of Thomas R. Brown, the entrepreneur whose family endowed her UA chair in bioengineering. The company tailors technology for specific uses and acts as a go-between for academics and the business world.

To survive in our bodies, pathogens must be smart. They need minerals and can't just go shopping for atoms of iron. So they find them in the pantry of their host, namely you. Our bodies have iron, but it is carefully hidden, because free iron is toxic. The wily pathogen knows exactly where to look: inside the body's iron-packaging device, a molecule called a heme. The hungry microbe will grab the whole heme and use the iron atom as food.

Knowing that behaviour, Powers' team sets a trap. It captures a pathogen, in the blood, urine, spit, in any context, with a clever kind of sensor. The heme becomes the trap, dangled on the end of a nanotether where a passing microbe in a drop of blood would bump into it and bond with it. Wash off the blood and you have captured a pathogenic microbe.

When all of that happens, you have a positive result. The principle applies not just to blood tests but to testing a sample of soil, rock or ice in a Mars-like extreme environment resembling outer space. Working with the NASA Spaceward Bound program, her tests have already demonstrated important information and may someday be adopted for a future Mars mission.

Powers has performed her surrogate space tests with portable field units in the Mohave Desert and in Chile's Atacama Desert, the driest place on earth. She says her team took instruments, filled with engineering marvels like optics, algorithms and control systems, to sample rocks and soil to determine if there is 'something living' there. And if the sampling points to something live, then, she says, other scientists would jump in and ask, 'Gee, I wonder what it is.'

The first test just involves shining light on the surface and analysing the light that comes back, a test that can distinguish live cells, dead cells and spores, a dormant form of microbes. If that test is positive, then a second test involves wiping a surface across the top of a rock, then shining a certain light on it to indicate whether it has captured microbes that suggest life. The Atacama Desert supports very little life as we know it, she says, but the Mohave Desert has significant levels.

Those are only some of the problems her lab is already tackling.

Over the horizon, she declares, are more dreams. 'I would like to develop, test, and deploy a cheap diagnostic for HIV, TB, and malaria, for field use in Third World countries,' she said, 'and just for pennies.' And while she's at it, she'd like to achieve one more landmark: 'Finding clear evidence that extraterrestrial life exists, or has existed, using our technology.'

Accomplishments

Linda S. Powers has a broad scope of expertise from biochemistry to electrical engineering, and has considerable experience in hemeprotein catalysis, structural biology and the design and construction of optical and X-ray instrumentation for biomedical applications.

Powers was a pioneer in the use of synchrotron radiation and X-ray absorption spectroscopy for the investigation of biological problems. Her current research areas include the development of microbe detection and capture technology.

She is Thomas R. Brown Professor of BioEngineering, professor of electrical and computer engineering, Biomedical Engineering Interdisciplinary Program faculty, and BIO5 faculty.

Before joining the UA in 2007, she was professor of electrical and computer engineering and professor of biological and irrigation engineering at Utah State University.

Dr. Powers was a member of the technical staff of AT&T Bell Laboratories from 1976 to 1988. She is a fellow of the American Physical Society and the American Institute of Chemists and her honors include the U.S. Bioenergetics Award of the Biophysical Society and the State of Utah Governor's Medal for Science and Technology.