Engineered protein hydrogels are promising candidates in many biomedical applications such as regenerative medicine and tissue engineering. While many studies have focused on controlling their mechanical properties, biofunctionality and stimuli responsiveness, less has been done to elucidate the dynamics of gels on a molecular scale. However, unraveling the diffusion and molecular relaxation of protein gels is critical to gain a better understanding on the self-healing properties and erosion behavior. Here, we report the first systematic experimental measurements on the diffusion behaviors of a model coiled-coil protein in gels by forced Rayleigh scattering (FRS) over different length scales. An unexpected “super-diffusion” is observed where the relation τ ~ d<sup>2α</sup> exhibits a pseudo power law in a log-log plot and the scaling exponent α is less than one. When the length scale is large, Fickian diffusion is recovered where an effective diffusion coefficient can be calculated. The anomalous diffusion is found be strongly dependent on temperature as well as the protein concentrations in gels. To quantitatively explain the experimental results, we have developed a "two-state" model, which considers both the diffusion of proteins and the exchange kinetics of the coiled-coil domains. The model is able to capture both diffusion regimes, and it yields estimated association parameters that can be used to obtain a collapsed shear rheology master curve from bulk mechanical measurement.

Unexpected anomalous diffusion in associating protein hydrogels

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.