Synthesis of novel supramolecular assemblies based on hyaluronic acid derivatives bearing bivalent β-cyclodextrin and adamantane moieties

New supramolecular assemblies based on hyaluronic acid stabilized by divalent beta-cyclodextrin/adamantane (beta-CD/AD) complexes were synthesized with the aim to compare their viscoelastic behavior in aqueous medium with systems resulting from monovalent complexes. For this purpose, dimers of AD and beta-CD to be coupled to hyaluronic acid were prepared by multistep chemical synthetic pathways. Investigation of the complexation properties of these dimers by isothermal titration calorimetry (ITC) experiments revealed a pronounced increase of the stability constant. These results can be attributed to divalency as suggested by the value of the complexation enthalpy (Delta H-0) which is twice that of the monovalent complex, in agreement with literature data. Nevertheless, a decrease of the complexation properties of these dimers when fixed on the polysaccharide backbone was observed as a result of an unfavorable entropy of binding. The viscoelastic properties of the supramolecular assemblies were examined by dynamic rheological measurements, showing different behaviors related to the nature and the energy of the interchain physical junctions.