Spesifik iyonların hiyalüronik asit ve kitosan arasındaki kompleksleşme üzerindeki etkisi

Complex coacervation is a liquid-liquid phase separation caused by the interaction of oppositely charged macromolecules and the entropy gain by counter-ions' release. Coacervation is shown to be influenced by a number of variables, including temperature, pH, ionic strength, the concentration and molecular mass of polymers, the charge density of polyelectrolytes, and the stoichiometry of the mixture. The understanding of interactions between the ions and polymers goes back to Hofmeister series based on ability of ions to precipitate proteins. The specific ion effects have also been studied for other biomacromolecules and polymers. Considering the ability to affect the stability and behavior of coacervates formed by charged polymers, the ion effects are therefore noteworthy in the context of complex coacervation. In this study, the impact of this series on the complexation and coacervation of hyaluronic acid (HA) with chitosan (CHI) at acidic pH has been investigated by light microscopy, turbidimetric titration, potentiometric titration and isothermal titration calorimetry (ITC) experiments. Light microscopy images were taken to demonstrate that the HA/CHI system formed coacervates. Turbidimetric titration experiments were utilized to investigate the coacervation process as a function of different salt types. The degree of ionization of HA and CHI was determined by potentiometric titration experiments. Isothermal titration calorimetry is applied to investigate the ion effects on the thermodynamics of HA/CHI complexation. Cation effects were investigated using chloride salts, whereas anion effects were investigated using sodium salts. Enthalpy values showed less change with monovalent cations whereas the enthalpy of complexation was found as more exothermic for magnesium ion than that of calcium ion. Acetate ion shows more exothermic enthalpy values compared to nitrate and chloride ions. The interactions between the two polyelectrolytes has the highest, most negative enthalpy values in the absence of salt.