Complexation of semi-flexible biopolyelectrolytes

Abstract

Complex formation and phase separation of two oppositely charged biopolyelectrolyte solutions were investigated by using turbidimetry. In our study, we have chosen to work with solutions of hyaluronic acid (HA), a polyanionic polysaccharide, and chitosan (CHI), a polycationic polysaccharide. There are many factors that affect the phase separation and the complexation of HA with CHI such as pH and ionic strength of the medium, polyacid/polybase charge ratio, molecular weight (chain length), and degree of deacetylation (DD) of chitosan. After mixing of these two polyelectrolyte solutions, the mixture became either clear or turbid, and formed flocculants, precipitates or coacervates. Among visual observation, turbidimetry helped us determine the onset of phase separation either at a certain pH, pHφ, or at a certain critical ionic strength, Ic. Aside from the complexation studies, potentiometric titrations were done to determine degree of ionizations of HA and CHI. In order to understand and differentiate between coacervation and precipitation, optical light microscopy was used.