Optical control of cell functions: Using laser light to remote control signalling, contraction and action potentials in living cells

The ultrashort pulsed near-infrared femtosecond laser has had a large impact in biomedical research fields and in microscopy, where it has enabled new imaging methodologies. At high intensities, the focused beam of a femtosecond laser has been used to irradiate specific locations inside a cell, often beneath the cell membrane, exploiting the inherent penetration and localized absorption that comes from the multiphoton absorption physics. This has been applied in photobleaching, photouncaging, laser surgery and other experiments where the light is used not merely for observation but is instead an integral tool to interact with the dynamics of cells, to probe and perturb the cell condition. In this talk I will discuss biological and mechanical effects that can be generated by short exposures to femtosecond laser irradiation, such as calcium waves, membrane hyperpolarization, and cell contraction. Both depolarization and hyperpolarization (Fig. 1) of the membrane potential could be evoked, depending on the laser parameters and on the position of the laser focus. These results have implications for the use of laser beams in microscopy, optical gene transfection, laser nanosurgery, and laser induced muscle contraction.