Repair of volumetric bone defects with a high strength BMP-loaded-mineralized hydrogel tubular scaffold

Efficient repair of critical-size volumetric bone defects remains a challenge due to the additional complicated surgery required for fixation. In this work, we first synthesized hydrogen bonding crosslinked supramolecular polymer (SP) hydrogels termed as P(NAGA-VPA) by copolymerizing two carefully selected monomers, N-acryloyl glycinamide (hydrogen bonding monomer) and vinylphosphonic acid (mineralization active monomer) directly in a concentrated aqueous solution. The P(NAGA-VPA) hydrogels were then subjected to in situ precipitation mineralization to generate novel high strength mineralized SP hydrogels. The concerted dual physical crosslinkages of NAGA H-bonds and nanocrystal–polymer interaction led to the best comprehensive mechanical performances with a tensile strength of over 1 MPa and a compressive strength of 5 MPa in an equilibrium swelling state. The mineralized SP hydrogel tubular scaffold was fabricated and encapsulated with bone morphogenetic protein-2 (BMP-2). The BMP-2-loaded mineralized SP hydrogel tube was finely sleeved over the murine radial defect without resorting to any additional surgical fixation. The outcome of 8-weeks implantation demonstrated that this hybrid tubular scaffold contributed to an efficient repair of volumetric bone defect by accelerating new bone formation and seamlessly bonding to the bone surface.