Study On Hyaluronic Acid Solutions And Freeze-Thaw Gels

Hyaluronic acid (HA) is a polyanion mucopolysaccharide, existing in almost all mammalian animals. Hyaluronic acid is naturally occurring in the body, biocompatible, biodegradable and non-immunogenic, which make HA and derivatives widely used in the medical field. Therefore studying the solutions, mixtures with other polysaccharides and gels properties help to improve current applications and develop new applications.HA solution with and without salt, mixtures with the polysaccharide as well as physical modifications of freezing-thawing gel are studied. We studied rheological properties of HA free salt solution and salt solution. Based on the physical scaling law, the effect of concentration on rheological parameter is discussed in this paper. Fitting curves of free salt HA solutions fall into two linear regions characterized by (?)sp(?)c1 and (?)sp(?)c3.5. For HA solution with 0.15 M NaCl, the fitting data can be divided into two linear regions characterized by (?)sp(?) c1 and (?)sp(?) c4.2, respectively, which is similar to neutral polymer. For the free salt HA solution, the unentangled concentration regime two decades in polymer concentration. In this regime the viscosity weakly increase with concentration following the scaling law: (?) - c1.2 and (?) - c1/2 (Fuoss law), which indicates the polyelectrolyte properties of HA solution. Three constitutive models, including the linear Maxwell viscoelastic model, non-linear PTT model and Giseskus model, were employed to describe the viscoelastic behavior of concentrated HA solutions in this study. All theoretical values calculated from three constitutive models could fit the experiment data quite well, indicating the models were applicable to describe quantitatively the rheological behavior of HA solution. Furthermore, Maxwell model is able to predict the experimental viscoelastic behavior very satisfactorily for different molecular weight HA aqueous solutions. Since the viscoelasticity of HA is of important functions and applications, the results of this study could not only help to understand the linear and non-linear viscoelasticity of HA solutions, but also provide an effective method to realize the quantitative prediction of the viscoelasticity of HA solution.Mixtures of HA with corn fiber gum(CFG) is studied for blending systems. HA and CFG are uniformly mixed in the applied concentrations and the rheological curves of mixed solutions are similar with pure HA, but the shear viscosity are larger than the algebraic sum of two separate components, showing a unique synergistic effect. We accordingly applied for a patent.We studied HA freezing-thawing gel physically modified by small molecule carboxylic acids, such as oxalic acid (OA), glutaric acid (GA) and citric acid (CA) through some research methods including rheology, FT-IR spectroscopy, optical microscopy and electron microscopy. Preliminary results of the present study showed that small molecules like OA are wrapped up into the gel and have some effect on process of the gel formation.