Once the job of electrons, stimulating heart cells is now being done by photons. Researchers at Osaka University (Osaka, Japan) have demonstrated the first optical pacemaker, which uses near-infrared pulses from a femtosecond Ti:sapphire laser to stimulate cardiomyocytesthe heart muscle cells responsible for contraction and relaxation, or beating, of the heartand induce periodic contraction cycles that allow the laser radiation to act as a pacemaker.
When 80 fs pulses from a 780 nm modelocked laser operating at a repetition rate of 82 MHz irradiate (via a microscope and optics) a single cardiomyocyte cell, fluorescence images record the intracellular calcium elevation responsible for mechanical contraction of the cell. If the exposure of this irradiation is limited to 8 ms at a 1 Hz periodic rate (in region “i”) by means of an optical shutter, groups of cardiomyocytes contract in phase with each other (regions “ii” through “v”) and then relax upon removal of the irradiation. This pacemaker-like operation was obtained at laser power levels between 15 and 30 mW. Data indicates that laser interaction with the cardiomyocyte contraction cycle is more of a triggering effect rather than an overriding control of normal cell function. Contact Nicholas Smith at [email protected].