(577b) Phase Behavior and Coacervation of Aqueous Polyelectrolyte Solutions

Dimitrios Priftis, Katie Megley, Matthew Tirrell^*.

Department of Bioengineering, University of California, Berkeley

^*E-mail: mvtirrell@berkeley.edu

Mixing of oppositely charged polyelectrolytes in aqueous solutions may result in the formation of polyelectrolyte complexes (PECs). Phase separation and complex coacervation of different polyelectrolytes was investigated in such solutions. The formation of PECs is strongly affected by the polyelectrolyte mixing ratio (stoichiometry), the ionic strength (salt concentration), the total polymer concentration, the pH and the temperature. Sample turbidity, which is an indicator of complex formation, was utilized for the study of the above factors. Discrimination between coacervate and precipitate was achieved by optical microscopy. The critical salt concentrations, required for the transition from coacervate to solution, were used for establishing phase diagrams as a function of polybase content and salt concentration. The viscosity of coacervates, formed from various polyelectrolytes mixtures, was measured with the use of a rheometer. Coacervates of PEI and PGANa or PAAsNa showed the typical viscoelastic behavior of polymer solutions, while coacervate viscosities depent on the salt concentration of the mixtures. The polymer rich coacervate phase was tested as a potential substrate for cell proliferation of fiber blast cells (NIH-3T3). Confocal microscopy was utilized to visualize cell interaction and proliferation on the coacervate surface. To optimize NIH-3T3 cell attachment specific bioactive peptide sequences such as (Lys)₅(Arg-Gly-Asp) were introduced in the coacervate substrates.