Calorimetric and light scattering study of interactions and macromolecular properties of native and hydrophobically modified hyaluronan

The paper presents a new investigation of a native and a hydrophobically modified hyaluronan (HMHA) C8NH-HA100 interactions with surfactants SDS, DTAB, and a dye polarity probe Coomassie Brilliant Blue (CBB), and their macromolecular properties in aqueous environment using isothermal titration calorimetry (ITC) and SEC-MALLS. A novel alkylated HA derivative was prepared by the introduction of octyl chains onto -OH groups of the HA d-glucuronic acid unit via carbamate bond at a high degree of substitution preserving the HA carboxylic groups. Large and abrupt endothermic enthalpy changes (ΔH) during the titration of HA by DTAB evidence a strong electrostatic interaction and a formation of complex aggregates between HA and DTAB micelles. Heat effects of HA-SDS titration are moderate and reveal a lowering of the surfactant CMC in the presence of HA. The C8NH-HA100 displays binding with CBB in terms of exothermic enthalpy changes, which is ascribed to hydrophobic interactions, while such binding is not observed for HA. The assessment of the polysaccharides backbone stiffness and the coefficient of the Mark-Houwink-Sakurada plot (MHS), a, by SEC-MALLS shows a little alternation of the HA backbone stiffness after its modification.