Effect of Polymer Gel Elasticity on Coacervate Phase Behavior

Polymer gels make up many biological systems and tissues such as the extracellular matrix in cartilage, skin, and vitreous in the eye. Their network structure and internal pressure have the capacity to influence structure formation, tissue biomechanics, and influence liquid phase separation. In order to investigate the effect of the elastic environment on biomacromolecular assembly, we have studied how varying gel modulus changes the phase behavior and radius of coacervate droplets. Poly-L-lysine (PLL) and hyaluronic acid (HA) coacervate phases were prepared in polyacrylamide gels of moduli varying from ~0.035 - 6.2 kPa. The size of the coacervate droplets is reported from Bright Field Microscopy and Confocal Microscopy. Fluorescence Microscopy is used to determine the concentration of fluorescently tagged HA in the coacervate and supernatant phases as a function of pH (2 – 10) and ionic strength (25 - 800 mM). Overall, with increasing shear modulus of the polyacrylamide gel, the coacervate droplet size decreases. By understanding how an elastic environment influences simple electrostatic assembly, we can further understand more complicated biomacromolecular assemblies.