Thermo-responsive peptide-modified hydrogels for tissue regeneration

Loosely cross-linked hydrogels consisting of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) were synthesized, characterized, and used as model scaffolds for studying cell-material interactions in three-dimensions (3D). The AAc groups were functionalized with peptides containing the -RGD- and -FHRRIKA- sequences found in bone sialoprotein. Chemical modification of th e hydrogels was verified via solid-state H-1 nuclear magnetic resonance spe ctroscopy, lower critical solution temperature studies, and volume change s tudies. The peptide-modified hydrogels were pliable at 22 degreesC and coul d be injected through a small-diameter aperture. Rat calvarial osteoblasts (RCO)seeded into the peptide-modified hydrogels were viable for at least 21 days of in vitro culture. The RCO spread more and demonstrated significant ly greater proliferation when cultured within the peptide-modified hydrogel s, as compared to control hydrogels. These peptide-modified P(NIPAAm-co-AAc ) hydrogels serve as useful tools for studying cell-material interactions w ithin 3D structures and have the potential to be used as injectable scaffol ds for tissue engineering applications.