Structurally Versatile Glycosaminoglycan Hydrogels for Biomedical Applications

Despite widespread use of hydrogels in biomedical devices, low moduli and brittleness of hydrogels has hindered applications with load bearing requirements. In this study, different molecular network design strategies (homopolymer, copolymer, and double network) were used to control the arrangement of macromers to tune the mechanical properties of glycosaminoglycan (GAG)-based hydrogels. The resulting changes in swelling ratio, crosslink density, and fracture properties of the gels were then investigated. It was hypothesized that increasing the number of polymerizable groups on the macromers methacrylated chondroitin sulfate (MCS) or methacrylated hyaluronic acid (MHA) and using oligo(ethylene glycol diacrylate) s to copolymerize with can improve the crosslinking by increasing the effectiveness of polymerization through the kinetic chains. By increasing the degree of methacrylation of MCS from 24 to 34 mol%, the swelling ratio q and the crosslink density rho(x) of 13 wt% MCS gel was changed from 210 to 44 g/g and from 230 to 740 mol/m(3), respectively. Despite improved rx and tuned q, the fracture strain of the homo- and copolymer gels remained fairly low (<25%), likely due to the highly extended conformation of glycosaminoglycans, and the microheterogeneity induced by the kinetic chains. However, using a DN double network design (with PAAm), the fracture strain and toughness of the gels were greatly improved as the fracture strain of 15 wt% MCS-PAAm DN increased more than 3 times, from 15 to 55%. The versatile physical and favorable biological properties of GAG-based hydrogels make them promising materials for many biomedical applications.