Investigating the Effects of Charge on the Release Kinetics of Charge-Modified Peptides from Gelatin Microparticles.

There has been a growing interest in the use of therapeutic peptides in tissue engineering and drug delivery applications. However, due to the small size of peptides, achieving controlled release over days to weeks from a hydrogel-based system without conjugation to the carrier has remained a challenge. In this study, charge modifications were introduced to a model osteogenic pentapeptide, osteogenic growth peptide (OGP), as associating peptide sequences, and to a gelatin microparticle carrier, as conjugating peptide sequences, to harness electrostatic interactions for controlled release. The charge of the conjugating peptide and gelatin did not affect the swelling and degradation of gelatin microparticles. The charge of the associating peptide and gelatin, but not the charge of the conjugating peptide, had significant effects on loading and release kinetics of an associating peptide-modified OGP. Notably, modulation of the electrostatic interactions between the carrier and the peptide enables controlled release for over 14-21 days.