Scheme 1

Schematic illustrations of design strategy for the PEGS/ICPN adhesive hydrogels and the application in distraction osteogenesis. a) Chemical structures of PEGS-NH2, γ-PGA and the process of in situ formation of CaP nanoparticles. PEGS-NH2 and γ-PGA can form chemically crosslinked structure in the presence of EDC/NHS via a coupling reaction. γ-PGA and the as-formed CaP nanoparticles can form physically crosslinked structure via γ-PGA chain-CaP nanoparticle physisorption together with -COO--Ca2+ ionic coordination. b) The process of distraction osteogenesis with the PEGS/ICPN hydrogels adhered to the zone of newly regenerative bone: (i) Multiple adhesion mechanisms formed between hydrogel and bone, including covalent amide bonds and -COO-- Ca2+ ionic coordination, contribute to the robust adhesion ability; (ii) The pro-osteogenic and pro-angiogenic effects of the PEGS/ICPN hydrogels in the DO process through recruitment and inducement of bone mesenchymal stem cells (BMSCs) and endothelial cells, enhancing regeneration and vascularization of the new bone