An ultrasensitive transducer for measurement of isometric contractile force from single heart cells

A novel ultrasensitive force transducer suitable for measuring isometric forces generated by single spindleshaped muscle cells is described. The transducer components are mechanically and electrically simple, consisting of a low power He-Ne laser, a pair of step index, glass optic fibers, and a photodiode detector circuit. To test the operation of the transducer, enzymatically isolated frog ventricular heart cells were used, having peak contractile forces on the order of 100 nN. The transducer presents a number of advantages over existing designs and has a resolution better than 2 nN. As such, it is suitable for excitation-contraction studies in single muscle cells.