Ultrafast dynamics in a live cell irradiated by femtosecond laser pulses

An ultrafast video microscope (UVM), the frame rate of which reaches one million per second has been developed. Our UVM system provides pictures with high-contrast and high-resolution for differential interference contrast (DIC), phase contrast, or dark field imaging. It allows us to observe fast events that occur in live cells when irradiated by ultrashort laser pulses. Femtosecond laser pulses can be used to manipulate, stimulate, and destroy specific cells and organelles under the microscope. The irradiation of such an intense laser immediately results in some physical events, such as microbubble generation, plasma formation, and photoporation. We investigate biophysical mechanisms underlying the ultrafast processes. Our data will contribute to development of new bio-imaging modalities, which implement laser cell transfection. We also present a new method to observe side views of live cells on a substrate. We used a polymer material CYTOP as the substrate for HeLa cells. CYTOP has a refractive index of 1.34, which is close to 1.33 of water. We investigate generation of microbubbles beneath the plasma membranes with a time resolution of one microsecond for the purpose of improving the efficiency of photoporation.