Dynamic Viscosity Measurement of Complex Coacervate with Hyaluronic Acid and Recombinant Mussel Adhesive Protein by Surface Force Apparatus (SFA)

Complex coacervation is a fluid-fluid phase separation, usually involving two oppositely charged polyelectrolytes in aqueous solution result a dense coacervate phase and a dilute equilibrium phase. Even though complex coacervate fluids are intensively utilized for encapsulation of various industrial products as well as for bimolecular processing in living organism, a systematic investigation of coacervate rheology had hardly performed. Here, varying weight ratio between hyaluronic acid (HA) and recombinant mussel adhesive protein (fp-151-RGD) from 0 to 1, we coacervated HA and fp-151-RGD and measured dynamic viscosity of complex coacervates by surface force apparatus (SFA). Depending on the mixing ratio between HA and fp-151-RGD for coacervation, viscoelastic fluid properties of the coacervate phase undergo transformation between shear thinning and shear thickening. At 25% (w/w) of HA, where the approximate maximum yield for HA/fp-151-RGD coacervation occurred, the coacervate showed shear thinning behaviors on SFA while the coacervate of lower coacervate yield points (10 & 40% (w/w)) behaved like a shear thickening fluid. Dependency of coacervate fluid properties on the weight ratio between two polyelectrolytes would be helpful to process polymeric fluids in aqueous solution for specific application in the industrial field as well as in the living organism.