Molecular and Rheological Characterization of Hyaluronic Acid
Three samples of the biopolymer hyaluronic acid (HA) were characterized in the following manner: the molecular weights were obtained via multi-angle laser light scattering; the intrinsic viscosities were calculated through dilute solution viscometry, and the rheology of HA solutions was determined with constant rate rotational viscometry and dynamical mechanical testing. In addition, the highly debated role of hyaluronic acid in wound healing was examined by studying the effect that HA has upon thrombin-catalyzed fibrin clotting. Fibrin, in phosphate-buffered saline, was clotted both alone and after being incubated with HA. It was determined that the presence of hyaluronic acid resulted in a slower clotting process; in effect, HA acts as an anti-coagulant. Based upon the experimental evidence, it is proposed that this anti-coagulant phenomenon arises through a combination of two mechanisms: 1) specific binding between HA and fibrin, which acts to retard fibrin clotting through steric hindrance, and 2) the formation of an HA network which slows fibrin clotting by hindering free diffusion of fibrin and thrombin. Finally, creation of a synthetic replacement for synovial fluid was attempted using xanthan gum and locust bean gum in phosphate-buffered saline. The phenomenon of gum synergism was utilized in an effort to exert some degree of fine-tuning over the final rheological properties of the solution. This also would provide the side benefit of reducing the weight of gum required per unit volume. By mixing the solutions at different temperatures, it was possible to exploit the tendency of xanthan gum to uncoil at higher temperatures and therefore bind more strongly to locust bean gum. However, it was determined that no combination of gum concentrations and processing conditions resulted in a gum solution that adequately mimicked the rheology of a hyaluronan solution.