Optically controlled contraction of photosensitive skeletal muscle cells.

As the skeletal muscle cell is an efficient force transducer, it has been incorporated in bio-microdevices using electrical field stimulation for generating contractile patterns. To improve both the spatial and temporal resolutions, we made photosensitive skeletal muscle cells from murine C2C12 myoblasts, which express channelrhodopsin-2 (ChR2), one of archaea-type rhodopsins derived from green algae Chlamydomonas reinhardtii. The cloned ChR2-expressing C2C12 myoblasts were made and fused with untransfected C2C12 to form multinucleated myotubes. The maturation of myotubes was facilitated by electrical field stimulation. Blue LED light pulse depolarized the membrane potential of a ChR2-expressing myotube and eventually evoked an action potential. It also induced a twitch-like contraction in a concurrent manner. A contraction pattern was thus made with a given pattern of LED pulses. This technique would have many applications in the bioengineering field, such as wireless drive of muscle-powered actuators/microdevices.