Controlled release of a tissue inducing peptide from oligo(poly(ethylene glycol) fumarate) hydrogels for orthopedic tissue engineering

The objective of this research is to develop injectable, in situ polymerizable polymer scaffolds for the controlled release of inductive factors for bone and cartilage tissue engineering. To that end, the novel polymer oligo(poly(ethylene glycol) fumarate) (OPF) was synthesized with varying poly(ethylene glycol) (PEG) chain lengths to create crosslinked networks of varying mesh size. A 23 amino acid peptide, TP508, was incorporated into OPF networks either directly or embedded in poly(DL-lactic-co-glycolicacid) (PLGA) microparticle carriers and the release kinetics of the TP508 was examined. After 30 hours, hydrogels of PEG chains of molecular weight 10,000 (PF10K) had released greater percentages of the total TP508 (53±3 wt% of directly loaded TP508) than those fabricated with PEG chain of molecular weight 1,000 (PF1K) (31±7 wt%). This effect was also observed upon the inclusion of PLGA microparticle carriers. For hydrogels of either PEG chain length, release of TP508 was greatly reduced with the use of microparticle carriers (6±1 and 2±1 wt% for PF10K and PF1K, respectively). Our results demonstrate that TP508 can be incorporated into OPF hydrogels and that the release kinetics of the peptide can be modulated through alterations in the scaffold mesh size and the use of a microparticle carrier.