Development of hydrogel-based platforms to investigate the mechanics and dynamics of active biological networks

This work focuses on exploring the potential of hydrogel-based materials and devices to control and study the feedback-driven responses of active cytoskeletal composites formed using actin, microtubules, motor proteins, and crosslinkers. We report our development of a measurement platform that uses monodisperse hydrogel microspheres created using microfluidic processing and photopolymerization. The spheres are elastic and are surface functionalized to enable adhesion to both glass substrates and proteins. When encased within an actively-contracting cytoskeletal composite material, the spheres can be deformed due to the stochastic application of contractile, compressive, and shear forces generated by kinesin and/or myosin motors. In this work, we develop protocols to tune the size, composition, and placement of the hydrogel spheres within a microfluidic channel. We show that it is possible to measure the sphere deformation using confocal microscopy and to quantitatively relate the sphere deformation to the applied stresses using a technique we call microsphere-based traction force microscopy, which can be implemented in a high throughput fashion. This high degree of synthetic control enables us to investigate the relationships between hydrogel geometry and stiffness and the resultant cytoskeletal response to elucidate mechanobiological circuits that underpin cytoskeletal dynamics.