Hyaluronan derivatives: chemical modification and biochemical applications

Seven sulphated hyaluronic acid (HA) derivatives, with a general formula HyalS(x) (x = 1, 2, 2.5, 3, 3.5, 3.8, and 4), were synthesised. Coagulation tests performed on these compounds yielded promising results for HyalS(2.5) to HyalS(4). The relationship of the anticoagulant activity of HyalS to chain length was also evaluated. HyalS(x) cytotoxicity and cytocompatibility were assessed by a direct contact method using L929 fibroblasts and human endothelial cells. Tests of HyalS(x) susceptibility to enzymatic degradation showed that the introduction of sulphate along the hyaluronic acid chain renders the macromolecules resistant to enzymatic digestion. The interaction of HyalS(x) derivatives with platelets was determined by platelet aggregation, activation, and von Willebrand Factor-dependent agglutination. Moreover, the ability of HyalS to form complexes with metallic ions such as Cu(II) and Zn(II) was evaluated together with the ability of these complexes to favour cell adhesion and stimulate cell migration. Various HyalS derivatives were immobilised by different chemical routes on the surface of polymeric materials and the physico-chemical and biological characteristics of the modified materials were studied. Lastly the therapeutic potential of Hyal hydrogels generated by a cross-linking reaction and then sulphated to improve their haemocompatibility, were evaluated in an animal model of articular inflammation.