Investigating Protein Hydrogel Mechanics through Force-Clamp Measurement and Validation with Dynamic Modeling

Proteins are the workhorses of our bodies, whose specific three-dimensional structure correlates to their function within the body. Protein hydrogels are a new type of material made from an interconnected network of these proteins, which naturally embrace a variety of biomedical applications, from scaffolding for artificial tissues to controlled drug delivery systems. When these hydrogels are exposed to external forces, the protein structure unravels and extends in a process called protein unfolding, affecting the unique mechanical properties characteristic of protein hydrogels. Here, we present an experimental technique to measure the force response of protein hydrogels in conjunction with a theoretical model which considers the protein folding phenomenon to describe their measured mechanical responses. Scaling the size of the simulated hydrogel reproduces the probabilistic to deterministic behavior characteristic of single-molecule unfolding, while varying the applied force expectedly leads to increases in the total extension and associated rate constants. Using a custom-made force clamp rheometer, we probe the unfolding and extension response of protein hydrogels and compare these results with our simulations. Ultimately, this technique and model could become valuable resources for helping to design and produce biomaterials with tunable elasticity. These biomaterials will find applications in mimicking tissues and organs within the body (such as the muscle contraction of the gut and heart), with the additional ability to controllably retain and release drugs from within their structure