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The ideal bone graft material must be biocompatible, biodegradable, osteoconductive and osteoinductive. In this study, a new biomimetic scaffold based on mineralized recombinant collagen, nano-hydroxyapatite/recombinant human-like collagen/poly(lactic acid) (nHA/RHLC/PLA), was prepared and the synthetic P24 peptide derived from BMP-2 was introduced into the porous nHA/RHLC/PLA scaffold to improve its osteoinductive property. The nHA/RHLC/PLA implants loaded with 3 mg, 2 mg, 1 mg and 0 mg P24 peptide were implanted subcutaneously into rats. At the 4th, 8th and 12th weeks after implantation, the rats were sacrificed in batch and the samples were harvested. Their osteogenic capability was detected by CT scan and histological observation. The results indicated that the osteogenic capability of 3 mg, 2 mg and 1 mg of the P24 peptide was superior to the implants without the P24 peptide. There was no significant difference between implants with 3 mg and 2 mg P24 peptide, but the osteogenic capability of the two dosage groups was significantly better than that of the 1 mg group. It was concluded that BMP-2-derived peptide can increase the osteoinduction of nHA/RHLC/PLA scaffold and the P24 peptide induced new bone formation in a dose-dependent manner. The nHA/RHLC/PLA scaffold loaded with the synthetic BMP-2-derived peptide is a kind of ideal scaffold material for bone tissue engineering.

Three-dimensional (3D) composite porous scaffolds containing hydroxyapatite (HA) and polymer matrix showed wide applications in bone repair because of their improved biocompatibility, bioactivity, and mechanical properties in our previous studies. In this work, mesoporous hydroxyapatite (MHA) surface-modified by poly­(γ-benzyl-l-glutamate) (PBLG) with different amounts (from 11 to 50 wt %) was synthesized by the in situ ring opening polymerization of γ-benzyl-l-glutamate N-carboxy anhydride (BLG-NCA) and then PBLG-g-MHA/PLGA composite films were prepared to illustrate the biological performance of the composites. Furthermore, porous scaffolds of PBLG-g-MHA/PLGA were fabricated through modified solvent casting/particulate leaching (SC/PL) method to demonstrate the ability of in vivo bone defect repair. In vitro cytological assay indicated that enhanced cell expansion on PBLG-g-MHA/PLGA with 11 wt % PBLG amounts and improved osteogenic differentiation on the composites with 33 and 50 wt % PBLG amounts were achieved. And the porous scaffolds exhibited high porosity and interconnected pores. Results of the in vivo rabbit radius defect repair indicated that rapid mineralization and new bone formation could be observed on the composites with 22 and 33 wt % PBLG. This study revealed that PBLG-g-MHA/PLGA composites might have potential applications in clinical bone repair.

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Osteonecrosis of the femoral head is a debilitating and painful orthopedic condition characterized by joint collapse. Salvage of the femoral head is highly desirable to preserve the contour and mechanical properties and prevent joint collapse. This study aimed to develop a new tissue-engineering approach for treatment of large bone defect in femoral head, that is, after osteonecrosis. The biphasic calcium phosphate (BCP) ceramic scaffolds were fabricated by a 3D gel-lamination technique based on micro-computed tomography (micro-CT) images of the cancellous bone microarchitecture of femoral heads. After seeding with autologous bone marrow-derived mesenchymal stem cells (BMSCs) in vitro, the cell-scaffold composite was implanted into a bone defect surgically induced in canine femoral head via trapdoor procedure, which was a common procedure for treatment of osteonecrosis. A total of 24 adult dogs were randomly divided into three groups (n = 8 each) for implantation of the BCP scaffold with or without with BMSCs, and also the autologous bone chips for comparisons. All animals were sacrificed at 30 weeks postoperatively and processed for radiological and histological evaluations. The contour of the femoral head was well preserved with implantation of BCP scaffolds with or without BMSCs, whereas joint collapse was found after treatment with autologous bone chips. The osteointegration and new bone formation was significantly greater with BCP scaffold implantation with than without BMSC seeding and showed greater strength and compressive modulus in the repair site. Micro-CT-based bone ceramic scaffolds seeding with BMSC might be a promising way to repair bone defects in the femoral head.

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Bone drilling is widely used in orthopedic surgery. Microcracks will be generated in bone drilling, which may cause fatigue damages and stress fractures. Fresh bovine cortical bones were drilled via vibrational and conventional ways. Drilling operations were performed by a dynamic material testing machine, which can provide the vibration while maintaining uniform feed motion. The drill site and bone debris were observed through scanning electron microscope (SEM). The experimental results showed that fewer and shorter micro-cracks were formed in vibrational drilling than those formed in conventional way. And the surface morphology of bone debris from two different drilling ways was also quite different. It is expected that vibrational drilling in orthopedic surgery operation could decrease the microdamage to the bone, which could lower the incidence of stress fracture and contribute to the postoperative recovery.

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