• hydrogel;
  • tyramine;
  • chondroitin sulfate;
  • tyrosinase;
  • photodynamic therapy


Tyrosinase-mediated crosslinking of chondroitin sulfate–tyramine (CS-TA) conjugates was successfully applied in the preparation of biodegradable in situ forming hydrogels under physiological conditions. Depending on the polymer concentration, the degree of substitution of TA residue and the tyrosinase concentration, the gelation times ranged from 2.3 to 129 min. Studies on the gel contents of CS-TA hydrogels showed that their degrees of crosslinking could be controlled by varying the tyrosinase concentrations. CS-TA hydrogels could be completely degraded by the chondroitinase ABC within a time range from 6 days to 11 weeks. CS-TA hydrogels possessed highly elastic properties and their storage moduli varied from 120 to 1300 Pa, as determined by rheological analysis. Scanning electron microscopy observation confirmed that CS-TA hydrogels contained a well-interconnected pore structure. A live–dead assay demonstrated that NIH 3T3 fibroblasts incorporated in CS-TA hydrogels retained their viability. In addition, in vitro release of methylene blue (a photodynamic therapy drug) from CS-TA hydrogels could be effectively sustained by the drug encapsulation in the hydrogels. This study indicates that tyrosinase-mediated in situ forming CS-TA hydrogels are promising for biomedical applications including drug release and tissue engineering. © 2012 Society of Chemical Industry