Theoretical Modeling and Experimental Characterization of the Rheological Properties of Biopolymer Gels with Active Biological Constituents
Thursday, February 27, 2025;
10:35am
CBEB 001
Speaker: Andrew Spakowitz from Stanford University
Biological systems are equipped with a diverse repertoire of proteins that perform molecular transformations with precision that is beyond the reach of conventional polymer chemistry. Such capabilities are exploited in living cells to enable large-scale transitions in behavior, and we can hijack these capabilities in engineered systems composed of biopolymers. In this talk, we discuss two such examples of biopolymer materials and present theoretical and experimental methods to interrogate their behavior. We present the Brachiation model, a molecular-level theory of a polymer network with dynamic associations that is rooted in experimentally controllable design parameters. We then discuss an engineered biopolymer material with precise kinetics of associations, and we use dynamic light scattering microrheology to measure the linear viscoelasticity across six decades in frequency. We then proceed to discuss our characterization of Olympic hydrogels composed of DNA rings that are topologically linked, and we demonstrate how proteins that unlink the DNA rings can modulate rheological behavior. Finally, we discuss the rheological behavior of an extracellular matrix containing breast cancer cells, and we characterize the reciprocal relationship between active forces from proliferating cancer cells and the frequency-dependent viscoelasticity of the stress-stiffening extracellular network. These results provide new insight into the non-equilibrium behavior of living systems and offer new strategies for exploiting the capabilities of living matter in soft material applications.
Andrew Spakowitz received his BS in Chemical Engineering from the University of Wisconsin – Madison in 1999, and he defended his PhD thesis in Chemical Engineering at the California Institute of Technology in 2004. He was a postdoctoral scholar in Molecular and Cellular Biology at the University of California, Berkeley from 2004 to 2006. Andrew Spakowitz joined the Department of Chemical Engineering at Stanford as an Assistant Professor in August 2006. He was promoted to Associate Professor in April 2014 and full Professor of Chemical Engineering and of Materials Science and Engineering in 2020. Professor Spakowitz currently serves as the Tang Family Foundation Chair of Chemical Engineering.
The Spakowitz lab is engaged in projects that address fundamental chemical and physical phenomena underlying a range of biological processes and soft-material applications. Current research in the lab focuses on four main research themes: chromosomal organization and dynamics, protein self-assembly, polymer membranes, and charge transport in conducting polymers. These broad research areas offer complementary perspectives on chemical and physical processes, and the Spakowitz lab leverages this complementarity to provide fundamental physical insight into these critical problems. Their approach draws from a diverse range of theoretical and computational methods, including analytical theory of semiflexible polymers, polymer field theory, continuum elastic mechanics, Brownian dynamics simulation, equilibrium and dynamic Monte Carlo simulations, analytical theory and numerical simulations of reaction-diffusion phenomena, and machine-learning and data-science approaches. A common thread in their work is the need to capture phenomena over many length and time scales, and flexibility in research methodologies provides them with the critical tools to address these complex multidisciplinary problems.
Hosted by: Angela Dixon, adc12@psu.edu
