In this work, we demonstrate how crude mucins, incapable of forming gels, may be restored to behave like natural mucus.

In this work, we report the development of a simplified method to perform microrheology to rapidly assess soft materials. This approach uses fluorescence polarization and a plate reader format to measure the rotational diffusion of nanoparticles within a sample of interest. We have established that this technique can be used to characterize a range of soft materials based on the rotational diffusion of nanoparticles in materials with viscosities exceeding 100 cP. Using these fluorescence polarization-based measurements, we describe formalism that enables the estimation of viscosity in polymer solutions and gels composed of polyethylene glycol, hyaluronic acid, and Matrigel after accounting for the length-scale dependent effects of the polymer environment on the nanoparticle rotational diffusion. Using this analysis, we show that the plate reader microrheology measurements of viscosity are in reasonable agreement with traditional particle tracking microrheology. The use of a plate reader format allows this approach to be higher throughput, less technically challenging, and more widely accessible than standard macro- and micro-rheological methods, making it available to non-experts. This approach has potential applications in clinical settings where conventional rheological equipment may not be available to rapidly characterize patient-derived samples.

We report the design of a mucin hydrogel created using a thiol-based cross-linking strategy. By using a cross-linking reagent capable of forming disulfide linkages between mucins, the mucinbased hydrogels possess viscoelastic properties comparable to native mucus as measured by bulk rheology. We confirmed disulfide cross-links mediate gel formation in our system using chemical treatments to block and reduce cysteines where we found mucin hydrogel network formation was inhibited and disrupted, respectively. Particle tracking microrheology was used to investigate the kinetics and evolution of microstructure and viscoelasticity within the hydrogel as it formed. We found that the rate of gel formation could be tuned by varying the mucin to crosslinker ratio, producing network pore sizes in the range measured previously in human mucus. The results of this work provide a new, simple method for creating mucin hydrogels with physiologically relevant properties using readily available reagents.