Development of a hydroxyapatite/collagen nanocomposite as a medical device.
The effect of cross-linking of a hydroxyapatite/collagen (HA/Col) nanocomposite, in which HA nanocrystals and collagen fibers are aligned like natural bone by a self-organization mechanism between HA and collagen in vitro, on mechanical properties was examined. The influence of degree of cross-linking, as well as rhBMP-2 preadsorption to the composite on the substitution pattern and rate with bone, was examined. In Experiment 1, anterior fusion was carried out at the C3-C4 vertebrae on 10 dogs and they were implanted as follows: without cross-linking and without adsorbed rhBMP-2 (three dogs), with cross-linking and without adsorbed rhBMP-2 (three dogs), without cross-linking and with adsorbed rhBMP-2 (two dogs), and with cross-linking and adsorbed rhBMP-2 (two dogs). Implants were removed from each dog for histology determinations after 12, 16, and 24 weeks in the non-rhBMP-treated groups, and after 16 and 24 weeks in the rhBMP-treated groups. In Experiment 2, the HA/Col composites with cross-linking and both with and without rhBMP-2 pretreatment were implanted into a bone defect of 20 mm made in the central part of tibiae in dogs (N = 3 in each group). As a control, bone defects of 20 mm remained without implantation (N = 3). The dogs were allowed to walk using an Ilizarov extra skeletal fixator. The implants were removed after 12, 16, and 24 weeks from one dog in each group. The cross-linking of the HA/Col composite was effective in controlling both the mechanical strength and bioresorbability. A "self-organization process" on the HA/Col implant surface resulted in the formation of bone remodeling units in and around the implant. Radiographic and histological findings suggest that a combined treatment of cross-linking of the HA/Col composite with preadsorption of rhBMP-2 molecules may be a very suitable replacement of existing ceramic systems in the anterior fusion of the cervical spine, as well as inlay grafting of bone defects in weight-bearing sites.
Itoh
Soichiro
S
Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8519, Japan. itoso.gene@cmn.tmd.ac.jp
Kikuchi
Masanori
M
Koyama
Yoshihisa
Y
Takakuda
Kazuo
K
Shinomiya
Kenichi
K
Tanaka
Junzo
J
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000737:chemistry; D018786:Bone Substitutes / Q000737:chemistry* / Q000627:therapeutic use; D001842:Bone and Bones / Q000293:injuries / Q000473:pathology / Q000601:surgery; D024042:Collagen Type I / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004285:Dogs; D006882:Hydroxyapatites / Q000737:chemistry*; D008422:Materials Testing; D016348:Osseointegration; D019736:Prostheses and Implants; D011994:Recombinant Proteins / Q000737:chemistry; D013123:Spinal Fusion / Q000379:methods; D016212:Transforming Growth Factor beta / Q000737:chemistry
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018786:Bone Substitutes; D024042:Collagen Type I; D003432:Cross-Linking Reagents; D006882:Hydroxyapatites; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2