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10 Jun 2005
Using femtosecond pulses to sever nerve connections in nemotodes could aid rapid screening of drugs.
Researchers in the US are using femtosecond laser pulses to sever nerve connections inside the tiny nematode worm C. elegans. According to the team, the beauty of this sub-micron scale surgery is that the nerves can grow back thanks to minimal damage caused by the femtosecond pulses.
"By cutting a few nano-scale nerve connections inside the nematode, we stopped the whole worm moving backwards," explained Adela Ben-Yakar from the University of Texas. "This delicate procedure keeps the surroundings of the severed nerves undamaged so that the nerves can grow back and the worms can move backwards again. This is the first time nerve regeneration has been seen in such a tiny organism."
In the past, ultraviolet nanosecond pulses have been used to study cells but this has some distinct problems. Ultraviolet wavelengths are strongly absorbed by cells leading to low-penetration depths and out-of-focus absorption. Nanosecond pulses with energies of several micro joules also cause photo-damage.
These problems can be overcome by using near-infrared femtosecond pulses which are focused to a small spot using a high numerical aperture objective lens.
Yakar and colleagues use a regenerative amplifier seeded by a Ti:Sapphire which produces 200 fs, 1 mJ pulses at a repetition rate of 1 kHz. The team says it succeeded in cutting single nerve fibers with pulse energies of only 10 - 40 nJ.
"The low repetition rate also reduces heat accumulation and thermal damage," say the authors. "We were able to cut individual processes within a few microns proximity to each other without damaging the nearby processes." They add that it takes less than a minute to find, position, focus and cut a single nerve fiber.
The team concludes by saying that its femtosecond technique should allow rapid screening of genes and molecules affecting nerve regeneration and development.
The team from Stanford University, the University of California at Santa Cruz and the University of Texas at Austin reported its work during the postdeadline session at CLEO 2005, Baltimore, US. (Paper reference: CPDA8)
Author
Jacqueline Hewett is technology editor on Optics.org and Opto & Laser Europe magazine.
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