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This issue...

  Brieflies

  View from the Inside

   Humble Weed Becomes Genome Model

   Microscopic Shock Waves

  Working Science

  People

  Site Seeing

  E-mail Reminder

Microscopic Shock Waves:

Part of New Technique for Rapid Chemical Analysis of Single Cell Contents

By Jo Lynn Draper

Scientists at the Beckman Laser Institute at the University of California, Irvine, have developed a breakthrough technique to analyze the contents of single living cells with subsecond time resolution. The technique uses a highly focused nanosecond laser microbeam pulse to generate a microscopic shock wave that disrupts the surface of the cell. The contents of the cell are immediately drawn into an electrophoresis capillary for analysis. (graphic 35kb)

This new technique will enable accurate measurement of cellular processes, such as functioning of enzymes in their native environment, by permitting precisely timed "snapshots" of intracellular composition.

Previous methods used to analyze single cells required mechanical or electrical manipulations that often resulted in artifacts leading to inaccuracies in the measurements. The techniques were also too slow, requiring times of the order of seconds to remove the cell contents for analysis, during which concentrations of metabolites of interest could undergo order-of-magnitude changes.

The new capillary electrophoresis (CE) method enables scientists to quantitate reactions that occur in subsecond times without altering or destroying the chemical makeup of the cell. The process begins with a cell cultured on a glass coverslip to allow viewing of the cell on an inverted microscope. A pulsed YAG laser beam is focused at the interface of the coverslip with a buffer surrounding the cell. The beam is placed near, but not coincident with the cell. A plasma is formed from the pulse, which in turn produces a cavitation bubble. The expansion and collapse of this bubble causes a shock wave that travels outward and interacts with the cell, disrupting cellular membranes. The cell contents are then loaded into an electrophoresis capillary; the analytes present in the cell are then separated within the capillary by the CE process.

The collaborating researchers, Nancy Allbritton, Christopher Sims, and Gavin Meredith from the Department of Physiology and Biophysics, and Tatiana Krasieva, Michael Berns, and Bruce Tromberg from the Beckman Laser Institute, are already taking the next steps--beginning studies of enzyme reactions that are central to cellular growth and development.

"This work will be applied to the mechanisms of how and why cancer cells grow and spread in an uncontrolled manner, and what might be done to control this unrestrained growth," Sims said.

This research was supported by DOE's Office of Biological and Environmental Research and the National Institutes of Health. The research is described in an article in the October 2, 1998, issue of Analytical Chemistry. Contact: Christopher Sims, University of California, Irvine, cesims@orion.oac.uci.edv.

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