In situ forming hydrogels based on tyramine conjugated 4-Arm-PPO-PEO via enzymatic oxidative reaction.

Over the past decades, hydrogels have been widely studied as biomaterials for various biomedical applications like implants, drugs and cell delivery carriers because of their high biocompatibility, high water contents and excellent permeability for nutrients and metabolites. Especially, in situ forming hydrogel systems have received much attention because of their easy application based on minimal invasive techniques. Chemical cross-linking systems fabricated using enzymatic reactions have various advantages, such as high biocompatibility and easy control of reaction rates under mild condition. In this study, we report enzyme-triggered injectable and biodegradable hydrogels composed of Tetronic-tyramine conjugates. The Tetronic-tyramine conjugates were synthesized by first reacting Tetronic with succinic anhydride and subsequent conjugation with tyramine using DCC/NHS as coupling reagents. The chemical structure of Tetronic-succinic anhydride-tyramine (Tet-SA-TA) copolymer was characterized by (1)H NMR and FTIR. The hydrogels were prepared from a Tet-SA-TA solution above 3 wt % in the presence of horseradish peroxidase (HRP) and H(2)O(2) under physiological conditions. Their mechanical property, gelation time, swelling ratio and degradation time were evaluated at different polymer, HRP, and H(2)O(2) concentrations. In addition, a cyto-compatibility study was performed using the MC3T3-E1 cell line. In the cytotoxicity test, it was clear that the Tet-SA-TA hydrogel had no apparent cytotoxicity except for the hydrogel formed with 0.25 wt % H(2)O(2) due to the cytotoxicity of residual H(2)O(2). In conclusion, the obtained results demonstrated that the Tet-SA-TA hydrogel has great potential for use as an injectable scaffold for tissue engineering and as a drug carrier for controlled drug delivery systems.