Sub-cellular nanosurgery in live cells using ultrashort laser pulses

We use femtosecond laser pulses to selectively disrupt the cytoskeleton of a living cell and probe its mechanical properties. The nanosurgery setup is based on a home-built two-photon microscope. To image, we use a 80-MHz, 100-pJ/pulse laser beam, which is scanned across the sample; to cut, we introduce a second, 250-kHz, 1 to 5-nJ/pulse, laser beam and locally ablate sub-cellular structures. Simultaneous cutting and imaging allows us to study immediate cellular response with several hundred-nanometer spatial and less than 500-ms time resolution.

We severed single actin bundles inside live cells to probe the local dynamics of the cytoskeleton and correlate it to global changes in cell shape. The targeted actin bundle retracts rapidly after laser cutting as it releases its tensile energy. We show that actin bundles in living cells behave like viscoelastic elements. This nanosurgery technique will further the understanding and modeling of stress and compression in the cytoskeleton network of live cells.