Nano-scissors lasers shows precise surgical capability

Dr. Adela Ben-Yakar, an assistant professor of mechanicalengineering at The University of Texas at Austin,led the development of the technique. It acts like a pair of tiny “nano-scissors,”able to cut, for example, nano-sized units like nerve axons, the parts of nervecells that carry nerve impulses away from the cells to muscles or to othercells.

“This tool opens up a new frontier for biologists studyingnerve regeneration,” says Ben-Yakar. “We can also apply it to many otherstudies that require nanosurgery, so it’s a very versatile tool.”

The beauty of this laser, she says, is its ability to cutorganelles (parts of cells—they are what organs are to organisms) precisely,without damaging surrounding tissue. Usually, conventional lasers used insurgery heat the area to be cut, then cut it, but this heightens the risk fortissue damage.

Ben-Yakar’s nanosurgery technique used a series oflow-energy “femtosecond” laser pulses to partially sever the axons of severalanesthetized C. elegans, a widely studied type of roundworm about onemillimeter long. A femtosecond is one millionth of a billionth of a second.

“The time is very important here,” she says. “Because ithappens so fast, there isn’t enough time for heat to diffuse out, so we don’tdamage anything. The pulse’s very short length makes the photons in the laserconcentrate in one area, delivering a lot of power to a tiny, specific volumewithout damaging surrounding tissue.”

Once cut, the axons vaporized, and no other tissue washarmed.

To assure the axons were actually cut, and theirdisappearance wasn’t caused by discoloration by the laser, the researchers cutaxons they knew would impair the worms’ backward motion. The worms couldn’tmove backwards after surgery. But within 24 hours, most of the severed axonsregrew and the worms recovered backward movement—confirming that the precisionof the laser’s cut didn’t damage surrounding tissue and allowed the neurons togrow a new axon to reach the muscle.

Until now, researchers have only been able to investigatenerve regeneration in mice and zebrafish, which have complex nervous systems.This laser allows researchers to study nerve cells at their most basicevolutionary form, opening the door to other experiments on genetic andmolecular factors that determine whether damaged nerve cells regrow.

Ben-Yakar developed the femtosecond laser surgery techniqueusing the laboratories and equipment of Dr. Robert Byer, a Stanford Universityprofessor, while doing post-doctoral work. The paper’s other co-authors areMehmet Fatih Yanik at Stanford, Hulusi Cinar, Hediye Nese Cinar and Andrew D.Chisholm at the University of California at Santa Cruz and Yishi Jin of UCSanta Cruz and the Howard Hughes Medical Institute.