Carbon nanotubes (CNTs) have been used in various fields as composites with other substances or alone to develop highly functional materials. CNTs hold great interest with respect to biomaterials, particularly those to be positioned in contact with bone such as prostheses for arthroplasty, plates or screws for fracture fixation, drug delivery systems, and scaffolding for bone regeneration. Accordingly, bone-tissue compatibility of CNTs and CNT influence on bone formation are important issues, but the effects of CNTs on bone have not been delineated. Here, it is found that multi-walled CNTs adjoining bone induce little local inflammatory reaction, show high bone-tissue compatibility, permit bone repair, become integrated into new bone, and accelerate bone formation stimulated by recombinant human bone morphogenetic protein-2 (rhBMP-2). This study provides an initial investigational basis for CNTs in biomaterials that are used adjacent to bone, including uses to promote bone regeneration. These findings should encourage development of clinical treatment modalities involving CNTs.

Bone morphogenetic proteins (BMPs) that have the potential to elicit new bone in vivo have been used in a tissue-engineering approach for the repair of bone injuries and bone defects. Although it is now possible to generate large amounts of recombinant human (rh) BMPs for medical use, the major challenge remains in the development of optimal local delivery systems for these proteins. Here we describe the development of a synthetic biodegradable polymer, poly-d,l-lactic acid-p-dioxanone-polyethylene glycol block copolymer (PLA-DX-PEG). This polymer exhibits promising degradation characteristics for BMP delivery systems and good biocompatibility under test conditions. PLA-DX-PEG/rhBMP-2 composite implants induced ectopic new bone formation effectively when tested in vivo, and can repair large bone defects orthotopically. This polymeric delivery system represents an advance in the technology for the enhancement of bone repair.

Bone morphogenetic proteins (BMP) induce bone formation in vivo, and clinical application in repair of bone fractures and defects is expected.However, appropriate systems to deliver BMP for clinical use need to be developed. We synthesized a new synthetic biodegradable polymer, poly-D,L-lactic acid-para-dioxanon-polyethylene glycol block copolymer (PLA-DX-PEG), to serve as a biocompatible, biodegradable polymer for recombinant human (rh) BMP-2 delivery systems. In animal experiments new bone was efficiently formed and a large bone defect was repaired using PLA-DX-PEG/rhBMP-2 composites. In addition, this new polymer could be used as an injectable delivery system for rhBMP-2. The rhBMP-2/PLA-DX-PEG composites also could be combined with other materials such as hydroxyapatite or titanium. This new synthetic polymer might be used for rhBMP-2 delivery in various clinical situations involving repair of bone, leading to great changes in orthopedic treatment.2

The MRI staging system provides accurate and reliable evidence for estimating ICRS classification and instability of COCD and is useful to decide appropriate treatment.

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