Femtosecond Laser Nano-Surgery for Nerve Regeneration Studies

Ultrashort laser pulses are increasingly being used to ablate subcellular structures inside living cells and multi-cellular organisms. We have recently demonstrated the feasibility of nano-axotomy in the nematode Caenorhabditis elegans (C. elegans) and observed nerve regeneration of the severed axons. Neural regeneration process can be impaired by the amount of collateral damage. Such damage is due to expansion of the thermoelastic stress-induced cavitation bubbles and the shock-waves expanding beyond the focal volume of the laser beam. This study presents a systematic characterization of the extent of damage in C. elegans created by 100-fs pulses at 1-kHz repetition rate with energies varying from 2-nJ to 20-nJ per pulse and the total number of pulses ranging from 1 to 1000. The minimum energy required for ablation greatly depends on the total number of pulses used. While a single shot of 21-nJ of energy can severe an axon, the threshold drops to as low as 3.8-nJ for 1000 pulses.