Bone growth around silicon nitride implants - An evaluation by scanning electron microscopy

Silicon nitride has demonstrated to be a potential candidate for clinical applications because it is a non-cytotoxic material and has satisfactory fracture toughness, high wear resistance and low friction coefficient. In this paper, samples of silicon nitride, which were kept into rabbits` tibias for 8 weeks, and the adjacentbone tissue were analysed by scanning electron microscopy in order to verify the bone growth around the implants and the interaction between the implant and the bone. Bone growth occurred mainly in the cortical areas, although it has been observed that the newly bone tends to grow toward the marrow cavity. Differences were observed between the implants installed into distal and proximal regions. In the first region, where the distance between the implant and the cortical bone is greater than in the proximal region, the osteoconduction process was evidenced by the presence of a bridge bone formation toward the implant surface. The results showed that silicon nitride can be used as biomaterial since the newly bone grew around the implants. (c) 2007 Elsevier Inc. All rights reserved.

Expression, Purification, Bioactivity, and Partial Characterization of a Recombinant Human Bone Morphogenetic Protein-7 Produced in Human 293T Cells

Bone morphogenetic protein-7 (BMP-7) is a secreted multifunctional growth factor of the TGF-beta superfamily, which is predominantly known for its osteoinductive properties and emerging potential for treatment of kidney diseases. The mature 34-38 kDa disulfide-linked homodimer protein plays a key role in the differentiation of mesenchymal cells into bone and cartilage. In this study, the full-length sequence of hBMP-7 was amplified and, then, cloned, expressed, and purified from the conditioned medium of 293T cells stably transfected with a lentiviral vector. The mature protein dimer form was properly secreted and recognized by anti-BMP-7 antibodies, and the protein was shown to be glycosilated by treatment with exoglycosidase, followed by western blotting. Moreover, the activity of the purified protein was demonstrated both in vitro, by alkaline phosphatase activity in C2C12 cells, and in vivo by induction of ectopic bone formation in Balb/c Nude mice after 21 days, respectively. This recombinant protein platform may be very useful for expression of different human cytokines and other proteins for medical applications.