Synthesis and characterization of MMP degradable and maleimide cross-linked PEG hydrogels for tissue engineering scaffolds

A series of poly(ethylene glycol) (PEG) hydrogels were successfully prepared via Michael-type addition between 4-arm PEG-maleimide (PEG-4MAL) and MMP degradable peptide. The gelation time was significantly short (∼10 min) in a low concentration of TEA (4 mM). Thermogravimetric analysis indicated the thermal stabilities of hydrogels. SEM images confirmed a porous structure and the pore size increased with the increase of the PEG chain length. Rheological measurements indicated that all the hydrogels exhibited the characteristics of elastomer and the cross-linking density had a correlation to the polymer weight percentage. After immersing in 0.9% sodium chloride injection, PEG hydrogels exhibited a good water absorption capacity, and their swelling ratio were directly related to the amount of cross-linking. Biological activities of the hydrogels were evaluated by in vitro enzymatic degradation and in vitro cell compatibility on mesenchymal stem cells (MSCs) and the results showed that the hydrogels were biocompatible and could be degraded by exogenously delivered MMPs or cell-secreted MMPs. Thus, PEG hydrogels exhibited the potential for tissue engineering scaffolds.