Paper Number
MF7 

Session
Micro/Nano Fluidics and Probe Rheology

Title
Probing the structure of mucin gels using microscale and macroscale rheometry

Presentation Date and Time
February 15, 2017 (Wednesday) 10:25

Track / Room
Track 3 / White Ibis

Authors (Click on name to view author profile)

1. Wagner, Caroline E. (Massachusetts Institute of Technology, Mechanical Engineering)
2. Turner, Bradley S. (Massachusetts Institute of Technology)
3. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
4. Ribbeck, Katharina (Massachusetts Institute of Technology, Biological Engineering)

Author and Affiliation Lines (in printed abstract book)
Caroline E. Wagner¹, Bradley S. Turner², Gareth H. McKinley¹, and Katharina Ribbeck^2
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; ²Massachusetts Institute of Technology, Cambridge, MA 02139

Speaker / Presenter 
Wagner, Caroline E.

Text of Abstract
Understanding the structural features of mucus, such as the average mesh size between interaction sites on its primary solid component, the large glycoprotein mucin, as well as the nature of these interactions is essential for understanding how mucus achieves its impressive barrier properties and how pathological cases arise. While the details of these features remain largely unresolved, it is known that the range of mechanical properties that mucus exhibits throughout the body depend on its intended physiological function, and arise because the local environment can mediate the strengths of a wide range crosslinking interactions which form the mucin network. In the present work we use a combination of macrorheological measurements and single particle tracking (SPT) probes in order to interrogate the details of the different association mechanisms from observed changes in the rheological response of a model system of 1wt% reconstituted MUC5AC mucins under various environmental conditions. Consistent with previous studies, our macrorheological tests show that the linear viscoelastic moduli of these mucin gels increase significantly as the pH is lowered from neutral to acidic. By studying the trajectories of individual particles of various sizes embedded in these gels, including the distributions of their step sizes and waiting times between steps, a clearer picture of the microstructural modifications leading to these bulk changes in mechanical properties can be gleaned. We show that even though traditional observations of ensemble-averaged microscopic thermal fluctuations in mucin gels are generally not predictive of their macroscopic linear viscoelastic response, detailed analysis of the non-Gaussian and non-Brownian nature of microparticle trajectories yields new insight into the structural and rheological details of mucin hydrogels.