A novel strategy for utilizing voice coil servoactuators in tensile tests of low volume protein hydrogels

We present a novel tensile testing system optimized for the mechanical loading of microliter volume protein hydrogels. Our apparatus incorporates a voice coil servoactuator capable of carrying out fixed velocity extension-relaxation cycles as well as extension step protocols. The setup is equipped with an acrylic cuvette permitting day-long incubations in solution. To demonstrate the functionality of the device, we photochemically crosslinked polyproteins of the I91 immunoglobulin domain from the muscle protein titin to create solid hydrogels that recapitulate elastic properties of muscle. We present data from tensile tests of these low volume biomaterials that support protein unfolding as a main determinant of the elasticity of protein hydrogels. Our results demonstrate the potential use of protein hydrogels as biomaterials whose elastic properties dynamically respond to their environment.