Study of the interaction between glucosamine hydrochloride and sodium dodecylsulphate micelles using conductometric, isothermal calorimetry, zeta-potential titrations, and NMR NOESY

The aim of this work was to investigate the influence of an anti-inflammatory agent, the bulky counterion named glucosamine (Gl ^+) , in sodium dodecylsulphate (SDS) in 2 ways: 1) by titration of SDS solutions with different concentrations of Gl ^+ ; and 2) by titration of Gl ^+ with SDS solution with concentration close to the critical micellar concentration (cmc) (7.7 mM). In procedure 1, micellisation study by isothermal titration calorimetry (ITC) showed that the increase in Gl ^+ concentration reduces the cmc and the micellisation enthalpy. Increasing of the micellisation entropy was also observed, suggesting desolvation of micellar structures as a consequence of electrostatic attraction with Gl ^+ ions. In procedure 2, titration of Gl ^+ with SDS solution at 7.7 mM showed the existence of 3 distinct ranges of glucosamine/SDS concentrations, which were attributed to I) Gl ^+ inducing micellisation, II) neutralisation of the micelles, and III) competition between the ions themselves in the micellar surface.