Design of a new device to measure skeletal muscle engineered tissues' contractile force by using an optical tracking technique

Tissue engineering is an interdisciplinary field that aims at the development of functional substitutes for damaged tissue. Since skeletal muscle is the most abundant tissue in the body, the possibility to increase the likelihood of success of muscle engineered tissues as a model of skeletal muscle become an interesting attraction. Within this context, it is useful monitoring the functional properties of the skeletal muscle engineered tissues during their growth and development. In this context, we approached the development of a new device for the measurement of skeletal muscle engineered tissues’ spontaneous contraction force in vitro, by using an optical tracking technique. Since muscle engineered tissues usually grow between two fixed pins, the working concept of our measurements is to have one of the pins, with a known elastic modulus, able to deflect. The pin deflection is measured by a tracking algorithm and then correlated with the contractile force through a calibration procedure. Thus, in this work, the tracking algorithm was validated for its accuracy in capturing the actual movement of the pin. A linear actuator was used to impose a known displacement at the end of the pin, and a high frequency camera mounted on a stereomicroscope was employed to acquire the images for post processing correlation. Our results showed a good algorithm accuracy for a range of displacement between 60 um and 200 um (corresponding to force values close to that of skeletal muscle engineered tissues) with relative percentage errors always lower than 5%. Accordingly to the experimental results, we proposed a correction of the tracking method that allowed us to have a further significant improvement, with error values always lower than 2%.