Potentiating bioactivity of BMP‐2 by polyelectrolyte complexation with sulfonated polyrotaxanes to induce rapid bone regeneration in a mouse calvarial defect

Bone reconstruction is a challenging issue in the regeneration of surgically removed bone and disease-related bone defects. Although bone morphogenetic protein-2 (BMP-2) has received considerable attention as a bone regeneration inducer, a high dose of BMP-2 is typically required due to its short life-time under in vivo conditions. We have proposed a method to enhance the osteogenetic differentiation ability of BMP-2 in vitro that is based on supramolecular polyelectrolyte complexation with sulfonated polyrotaxanes (PRXs) consisting of sulfopropyl ether (SPE)-modified α-cyclodextrins threaded along a poly(ethylene glycol) chain capped with terminal bulky stopper molecules. In this study, we evaluated the in vivo bone regeneration ability of the SPE-PRX/BMP-2 complexes in a mouse calvarial defect model in comparison to free BMP-2 and heparin/BMP-2 complexes. The regenerated bone area was determined by X-ray computed microtomography, and the mice implanted with sulfonated PRX/BMP-2 complexes exhibited rapid and significant bone regeneration compared to those implanted with free BMP-2 and heparin/BMP-2 complexes. We concluded that the sulfonated PRX/BMP-2 complexes are a promising candidate for clinical bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1355–1363, 2017.