Abstract
Devices for in vitro culture of three-dimensional (3D) skeletal muscle tissues have multiple applications, including tissue engineering and muscle-powered biorobotics. In both cases, it is crucial to recreate a biomimetic environment by using tailored scaffolds at multiple length scales and to administer prodifferentiative biophysical stimuli (e.g., mechanical loading). On the contrary, there is an increasing need to develop flexible biohybrid robotic devices capable of maintaining their functionality beyond laboratory settings. In this study, we describe a stretchable and perfusable device to sustain cell culture and maintenance in a 3D scaffold. The device mimics the structure of a muscle connected to two tendons: Tendon-Muscle-Tendon (TMT). The TMT device is composed of a soft (E ∼ 6 kPa) porous (pore diameter: ∼650 μm) polyurethane scaffold, encased within a compliant silicone membrane to prevent medium evaporation. Two tendon-like hollow channels interface the scaffold with a fluidic circuit and a stretching device. We report an optimized protocol to sustain C2C12 adhesion by coating the scaffold with polydopamine and fibronectin. Then, we show the procedure for the soft scaffold inclusion in the TMT device, demonstrating the device's ability to bear multiple cycles of elongations, simulating a protocol for cell mechanical stimulation. By using computational fluid dynamic simulations, we show that a flow rate of 0.62 mL/min ensures a wall shear stress value safe for cells (<2 Pa) and 50% of scaffold coverage by an optimal fluid velocity. Finally, we demonstrate the effectiveness of the TMT device to sustain cell viability under perfusion for 24 h outside of the CO2 incubator. We believe that the proposed TMT device can be considered an interesting platform to combine several biophysical stimuli, aimed at boosting skeletal muscle tissue differentiation in vitro, opening chances for the development of muscle-powered biohybrid soft robots with long-term operability in real-world environments.