Modeling release from degradable PEG hydrogels and their application in the delivery of osteoinductive growth factors

Multifunctional macromers based on poly(ethylene glycol) were photopolymerized to form degradable hydrogel networks. The degradation behavior of the highly swollen gels was characterized by monitoring changes in their degree of swelling and compressive modulus. Experimental results show that the modulus decreases exponentially with time, while the volumetric swelling ratio increases exponentially. A degradation mechanism assuming pseudo first-order hydrolysis kinetics and accounting for the structure of the crosslinked networks successfully predicted the experimentally observed trends in these properties with degradation. Once verified, the proposed degradation mechanism was extended to correlate network degradation kinetics, and subsequent changes in network structure, with release behavior of bioactive molecules from these dynamic systems. Finally, the application of these macromers as in situ forming hydrogel constructs for the delivery of osteoinductive growth factors and the production of mineralized tissue was demonstrated in vivo.