Engineered skeletal muscle tissue has the potential to be used as dual use actuator and stress-bearing material providing numerous degrees of freedom and with significant active stress generation. To exploit the potential features, however, technologies must be established to generate mature muscle strips that can be controlled with high fidelity. Here, we present a method for creating mature 3-D skeletal muscle tissues that contract in response to optical activation stimuli. The muscle strips are fascicle-like, consisting of several mm-long multi-nucleate muscle cells bundled together. We have found that applying a tension to the fascicle-like muscle tissue promotes maturation of the muscle. The fascicle-like muscle tissue is controlled with high spatiotemporal resolution based on optogenetic coding. The mouse myoblasts C2C12 were transfected with Channelrhodopsin-2 to enable light (∼470 nm) to control muscle contraction. The 3D muscle tissue not only twitches in response to an impulse light beam, but also exhibits a type of tetanus, a prolonged contraction of continuous stimuli, for the first time. In the following, the materials and culturing method used for 3D muscle generation is presented, followed by experimental results of muscle constructs and optogenetic control of the 3D muscle tissue.

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