Gels are key materials in biological systems such as tissues and may control biocondensate formation and structure. To further understand the effects of elastic environments on biomacromolecular assembly, we have investigated phase behavior and radii of coacervate droplets in polyacrylamide (PAM) networks as a function of the gel modulus. Poly-L-lysine (PLL) and sodium hyaluronate (HA) coacervate phases were prepared in PAM gels with moduli varying from 0.035 – 9.0 kPa. The size of the coacervate droplets is reported from brightfield microscopy and confocal fluorescent microscopy. Overall, the coacervate droplet volume decreases inversely with the modulus. Fluorescence microscopy is used to determine the phase behavior and concentration of fluorescently tagged HA in the coacervate phases as a function of ionic strength (100 - 250 mM). We find the critical ionic strength and coacervate stability is nonmonotonic as a function of the network modulus and that the local gel concentration can be used to control phase behavior and coacervate droplet size scale. By understanding how elastic environments influence simple electrostatic assembly, we can further understand more complicated biomacromolecular assemblies like collagen in the extracellular matrix. We have also observed how collagen assembly is limited in PAM networks using cryogenic electron microscopy and high resolution optical microscopy, and find that even in extremely crosslinked networks, collagen assembles, and the radial size and orientation is determined by the network topology.
Dr. Svetlana Morozova is an Assistant Professor of Macromolecular Science and Engineering at Case Western Reserve University. Dr. Morozova’s lab is broadly focused on studying polymer dynamics in solutions and gels by setting up new scattering and microscopy techniques. A particular interest in the lab is the effect of polymer flexibility on bulk properties such as viscosity and modulus, and polymer dynamics and assembly in complex environments. These processes are relevant to protein dynamics in cells, fluid flows, droplet formation, and filtration devices. Recently, Dr. Morozova has been awarded the ACS PRF Doctoral New Investigator, Lubrizol Innovation Prize, and NSF CAREER awards. Before joining CWRU in July 2019, Dr. Morozova worked as a post-doctoral researcher in the Department of Chemistry at University of Minnesota Twin Cities. She received her Ph. D. in Polymer Science and Engineering from University of Massachusetts at Amherst in 2017.