Single-pulse cell stimulation with a near-infrared picosecond laser

We have demonstrated stimulation of living cells by picosecond laser pulses. HeLa cells were exposed to focused 1.7ps pulses in a pulse train of between 1 and 16 pulses with different repetition rates. The pulses were generated by a titanium–sapphire laser and regenerative amplifier with a wavelength of 775nm. Contrary to expectation, we found that for a short pulse train (between 1 and 16 pulses at differing repetition rates), only the first pulse is responsible for triggering intracellular Ca2+ waves. These results show that the technique can be used to stimulate a calcium response in a living cell without thermal energy depositions.