Controlled remodeling of a protein-polysaccharide mixed gel: examples of gelatin-hyaluronic acid mixtures

The gelation of gelatin was studied in the presence of a polysaccharide, hyaluronic acid through rheology measurements. The influence of the polysaccharide on the obtaining of two different gel networks was evaluated: a chemical gel due to enzyme-catalyzed covalent bonding and of a physical gel due to triple helix formation induced by a temperature decrease were both formed in presence of hyaluronic acid. At the liquid state, the rheological properties (shear thinning/viscoelasticity) of the protein-polysaccharide mixture are dictated by the polysaccharide while gelatin modifies viscosity only from a quantitative point of view. Hyaluronic acid does not modify the gelation mechanism of gelatin. It is mainly present in the sol phase of the protein gel where it induces an entangled state which influences the overall viscoelasticity of the system. The impact of the polysaccharide enzymatic degradation on the mechanical properties of the mixture has been evaluated. Hyaluronidase allows a controlled modification of the loss modulus without affecting the storage modulus of gelatin gels. These experiments demonstrate that the mechanical properties of a mixed hydrogel can be a controlled through enzymatic remodeling.