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Ultra-fast shocks scramble cells
Powerful electrical pulses might zap tumours.
16 March 2004 HELEN PEARSON

Nanopulses can make cells commit suicide. SPL

Using very short, very powerful electric shocks, researchers are developing a way to jolt cancer cells into committing suicide, or healthy cells into healing wounds.

The technique involves blasting cells with nanopulses. These are high-power electrical bolts that last a few billionths of a second. They deliver millions of volts - enough to light up a city, but each burst lasts much less than the blink of an eye.

Longer shocks blow a cell apart, but researchers have found that the fleeting nanopulses leave the cell membrane unaffected while mixing up its insides. Now they are working out how to vary the timing and intensity of the shocks to make cells behave in specific ways.

In some of the latest work, Karl Schoenbach and Stephen Beebe of the Center for Bioelectrics in Norfolk, Virginia, have shown that the pulses can make blood platelets clump together in the first stages of clotting. This is something that might ultimately accelerate wound repair.

But there is plenty to be worked out before the human body is zapped with nanopulses. James Weaver, who studies electrical effects in cells at the Massachusetts Institute of Technology, Boston, says they are at an early stage: "There are maybe ten papers published showing that something dramatic is happening."

Cell shock

Biologists already treat cells with mild electric shocks in the laboratory, a technique called electroporation. These shocks make temporary punctures in cell membranes so that cells can be pumped full of experimental genes or proteins.

Schoenbach and his colleagues were the first to recognise that you could use high-power, brief shocks to manipulate cells in other ways. Working with electrical engineers in the late 1990s, they discovered that such pulses fry bacteria and sterilize contaminated water.

One of the most significant discoveries was that nanopulses make mammalian cells commit suicide, rather than blowing them up. This is a relatively gentle way of killing, because scavenger cells come and swallow the debris. By contrast, long electric shocks explode cells and liberate toxic molecules that cause inflammation and pain.

For this reason, researchers hope to use nanopulses to kill cancer cells while leaving healthy tissue intact. Schoenbach's team has already shown that the pulses can shrink mouse tumours by over 50%, and is working on catheters or non-invasive ways to deliver the shocks to the body.

Quite how nanopulses trigger cell suicide still leaves scientists scratching their heads. One idea is that the shock flips molecules in the cell membrane from the inside to the outside, which tells surrounding cells of their imminent death. "It says 'get rid of me,'" says Thomas Vernier, who is studying the technique at the University of Southern California, Los Angeles.

However they work, the nanopulses are prompting a flurry of ideas for their use. They might replace liposuction as a way to demolish unwanted flab, or blast away the fatty plaques that cause heart disease. "It is like asking what to do with a newborn baby," says Weaver. "Our speculations probably will not pick up the most important things."

Nature News Service / Macmillan Magazines Ltd 2004