Modularly engineered alginate bioconjugate hydrogel as biocompatible injectable scaffold for in situ biomineralization

In the present study, a type of bioconjugate was synthesized by post modification of alginate by conjugating temperature-responsive poly(epsilon-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(e-caprolactone-co-lactide) and O-phosphorylethanolamine as phosphorylation functional groups. Freely flowing bioconjugate sols at low temperature can transform to stable viscoelastic gels at the physiological temperature (37 degrees C). Subcutaneous administration of temperature-responsive bioconjugate sols into the dorsal region of Sprague-Dawley rats formed in situ hydrogel. in situ formation of bioconjugate gels in stimulated body fluids at 37 degrees C showed nucleation and hydroxyapatite mineral growth. Furthermore, hydroxyapatite growth was also found in in vivo gels, which suggested the potential of alginate-based bioconjugate gels as a scaffold for bone engineering. Bone morphogenetic protein 2 (BMP-2)-loaded bioconjugate formed stable gel in vivo, and demonstrated sustained release. BMP-2-loaded bioconjugates exhibited in situ biomineralization in vivo. These results imply that the in situ formation of injectable biomimetic materials has potential for bone tissue engineering applications.