Biological hydrogel synthesized from hyaluronic acid, gelatin and chondroitin sulfate by click chemistry

In order to mimic the natural cartilage extracellular matrix, which is composed of core proteins and glycosaminoglycans, a biological hydrogel was synthesized from the biopolymers hyaluronic acid (HA), chondroitin sulfate (CS) and gelatin via click chemistry. HA and CS were modified with 11-azido-3,6,9-trioxaundecan-1-amine (AA) and gelatin was modified with propiolic acid (PA). The molecular structures were verified by 1H nuclear magnetic resonance, infrared spectroscopy and elemental analysis, giving substitution degrees of 29%, 89% and 44% for HA-AA, CS-AA and gelatin-PA (G-PA), respectively. The -N3 groups of HA-AA and CS-AA were reacted with the acetylene groups of G-PA, catalyzed by Cu(I), to form triazole rings, thereby forming a cross-linked hydrogel. The gelation time was decreased monotonically with increasing Cu(I) concentration up to 0.95 mg ml−1. The hydrogel obtained was in a highly swollen state and showed the characteristics of an elastomer. Incubation in phosphate-buffered saline for 4 weeks resulted in a weight loss of up to 45%. Moreover, about 20% gelatin and 10% CS were released from the hydrogel in 2 weeks. In vitro cell culture showed that the hydrogel could support the adhesion and proliferation of chondrocytes.