Mechanical properties and degradation behaviors of hyaluronic acid hydrogels cross-linked at various cross-linking densities

The effect of cross-linking density of hyaluronic acid (HA) hydrogels on mechanical properties and degradation behaviors has been investigated. HA hydrogels were prepared by the covalent cross-linking of HA with poly(ethylene glycol)-diamine with two different molecular weights at various cross-linking densities. The elastic modulus increased gradually as the theoretical cross-linking density of HA hydrogels increased from 0% to 20%. However, as the theoretical cross-linking density increased above 20%, the elastic modulus decreased. At a theoretical cross-linking density of 20%, the elastic modulus increased as the molecular weight of the cross-linking molecule decreased. In vitro degradation rates of HA hydrogels decreased as the molecular weight of the cross-linking molecule decreased at a theoretical cross-linking density of 20%. The degradation rate of the cross-linked HA hydrogels decreased with increases in the theoretical cross-linking density from 0% to 20%. However, there was no significant difference in the degradation rate as the theoretical cross-linking density increased above 30%. With controllable mechanical properties and degradation rates, the developed HA hydrogels would be further investigated for various medical applications.