Interdisciplinary Team Traps Cells for Studies with "Optical Tweezers"

Interdisciplinary Team Traps Cells for Studies with "Optical Tweezers"

Davidson's Optical Tweezer team at the work bench -- (l-r) Karen Bernd, Rachel McCord '04, and John Yukich.

by Jeremy Hunt

Despite the name, “optical tweezers,” you can’t use this tool for plucking your eyebrows. As a matter of fact, you definitely don’t want it anywhere near your eyes! This new high-tech tool in Davidson’s Baker Watt Science Complex features an infrared laser beam that would blind anyone who looked into it. But when tightly focused into a microscope by a series of lenses, the beam can trap cells or even molecules to assist scientists in their studies of physics and cellular biology.

Davidson’s optical tweezers, a three-foot square metal peg board bristling with scientific attachments, was constructed by Rachel Patton McCord ’04 in association with John Yukich, assistant professor of physics, and Karen Bernd, assistant professor of biology. The device focuses the laser light on an individual cell on a microscope slide, holding it in place with energy and enabling researchers to manipulate it independently from surrounding material.

The custom-built device is one of very few on undergraduate campuses, and was made possible only through McCord’s interest and dedication, the cooperation of her professors, and funding from the Duke Endowment. A poster that McCord presented recently at a regional meeting of the American Physical Society about her optical tweezers won second place among twenty undergraduate posters. She will present another poster about the project next February at a national meeting of the American Biophysical Society.

McCord has been using the device to study the swimming force generated by flagellated algae that are the subject of research in Bernd’s laboratory. McCord explained that the study involves trapping individual algae cells in the laser trap. The cell tries to swim freely, but is unable to overcome the power of the laser. McCord then reduces the power of the laser gradually until the cell is able to escape. By determining the power of the laser beam at that moment of escape, McCord also knows the force that the flagella generate.

Bernd said that this basic research on algae flagella may yield information helpful to the study of cilia in human lungs and noses, which are similar. She also explained that this sort of research is key for potential developments in nano-technology, a field that endeavors to take machinery to microscopic proportions. She said, “In order to monitor the effectiveness of motors built at the ultra-micro scale, you need to be able to predict how much force you can expect. This is complicated by the fact that the motor’s small size magnifies the effect its environment has on its actions, even if that environment is ‘pure’ water. Think of the additional complications of a motor expected to work in the much more cluttered environment of an oil spill or a living organism. Since our best efforts in nanotechnology will only approximate nature, studying natural cellular machinery of a similar size will allow us to better estimate what the best man-made motors can achieve.”

The optical tweezer project has helped McCord bridge her academic interests in science and math. She started looking into graduate programs in biophysics, and then decided to construct her own major in that field through Davidson’s Center for Interdisciplinary Studies. The optical tweezers project is her senior thesis and the culmination of that major. After completing her thesis project and graduating, McCord plans to continue her study of biophysics toward a career in either academics or research.

It was also a dream-come-true for Yukich, who has a long-standing interest in cellular biology to accompany his expertise in laser physics. He helped McCord obtain an internship at the National Institutes of Standards and Technology in Washington, D.C., last summer, where one of her projects involved rebuilding an optical tweezer device. She recalled, “It was a trial by fire, but I gained valuable experience with the alignment of the beams and operating the tweezers.”

McCord’s interest, and the Duke Endowment funding, allowed Yukich to push ahead with construction of the device in the early part of this school year. The tweezers will remain at Davidson after McCord’s graduation to serve future Davidson students and researchers. Bernd plans to explain the application to students in her introductory biology classes, and believes other uses will be developed in areas like genomics and genetics.

Davidson is a highly selective independent liberal arts college for 1,600 students. Since its establishment in 1837, the college has graduated 23 Rhodes Scholars and is consistently ranked in the top ten liberal arts colleges in the country by U.S. News and World Report magazine. Davidson is engaged in “Let Learning Be Cherished,” a $250 million campaign in support of student financial assistance, academic resources, and community life.

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