Preparation of gels from hyaluronate solutions.

Stable, transparent gels can be prepared from hyaluronate solutions by adding CuSO4. The best gelation was found using solutions of 2 mg/ml hyaluronate in glass-distilled water at a pH of 6.2 after the addition of 1 mg/ml CuSO4. Methylation of the carboxyl groups of the hyaluronate completely abolished the gelation, indicating the importance of the carboxyl groups for the gel formation with Cu2+ ions. Gelation also depends on the molecular size of the hyaluronate, since hyaluronate was not able to form a gel after depolymerization with hyaluronidase.