One pot preparation of chitosan/hyaluronic acid-based triple network hydrogel via in situ click reaction, metal coordination and polyion complexation in water

Development of biopolymer hydrogels with multiple networks is regarded as a way to obtain gel strengths with bio-related properties. The present work, for the first time, demonstrates preparation of one pot triple network hydrogel of chitosan (CS) and hyaluronic acid (HA) (HA-triazole/CS-Cu(II) gel), formed by triazole linkage, metal-coordination, and CS-HA polyion complexation. The salt containing water system favors polyion complex formation of CS and HA without precipitation. HA functionalized with alkyne and azide groups in aqueous EDC/NHS allows crosslinking of HA via triazole linkage using Cu(I) azide-alkyne Click chemistry (CuAAC). The required Cu(I) catalyst is generated from Cu(II) in the CS-Cu complex upon addition of sodium ascorbate. The CS/NHS system leads to the solubilization of CS, thus enabling ionic gelation. The mechanical properties and morphologies can be controlled by simply varying the CS-HA mole ratios. In addition, the CS-HA triple-network (TN) hydrogels show biocompatibility based on studies with chondrocyte cells.