Improved osteoblast proliferation, differentiation and mineralization on nanophase Ti6Al4V.

BACKGROUND: Previous studies have demonstrated increased functions of osteoblasts on nanophase materials compared to conventional ceramics or composites. Nanophase materials are unique materials that simulate dimensions of constituent components of bone as they possess particle or grain sizes less than 100 nm. However, to date, interactions of osteoblasts on nanophase materials compared to conventional metals remain to be elucidated. The objective of the present in vitro study was to synthesize nanophase metals (Ti6Al4V), characterize, and evaluate osteoblast functions on Ti6Al4V. Such metals in conventional form are widely used in orthopedic applications. METHODS: In this work, nanophase Ti6Al4V surfaces were processed by the severe plastic deformation (SPD) principle and used to investigate osteoblast long-term functions. Primary cultured osteoblasts from neonatal rat calvaria were cultured on both nanophase and conventional Ti6Al4V substrates. Cell proliferation, total protein content, and alkaline phosphatase (ALP) activity were evaluated after 1, 3, 7, 10 and 14 days. Calcium deposition, gene expression of type I collagen (Col-I), osteocalcin (OC), osteopontin (OP) and the production of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta 1 (TGF-ß1) were also investigated after 14 days of culture. RESULTS: Functions of osteoblasts including proliferation, synthesis of protein, and ALP activity were improved on the nanophase compared to the conventional Ti6Al4V. The expression of Col-I, OC and OP mRNA was also increased on nanophase Ti6Al4V after 14 days of culture. Calcium deposition was the same; the average number of the calcified nodules on the two Ti6Al4V surfaces was similar after 14 days of culture; however, highly significant size calcified nodules on the nanophase Ti6Al4V was observed. Of the growth factors examined, only TGF-ß1 showed a difference in production on the nanophase surface. CONCLUSION: Nanophase Ti6Al4V surfaces improve proliferation, differentiation and mineralization of osteoblast cells and should be further considered for orthopedic implant applications.

[In vivo effect of nanophase Ti6Al4V on osseointegration: experiment with rabbits].

OBJECTIVE: To evaluate the effect of nanophase Ti6Al4V substrates on the osseointegration in vivo. METHOD: Novel nanophase Ti6Al4V substrates were prepared according to the severe plastic deformation principle. Eighteen New Zealand white rabbits were randomly divided into 3 equal groups with their trochanters of femur exposed and implanted with titanium substrate with common surface (Ti group), nanophase Ti6Al4V substrate (nano-Ti group), and hydroxyapatite-coated substrate (HA group) respectively. Four, 8, and 12 weeks later X-ray films were taken on 6 rabbits from each group, tetracycline and calcein were injected intramuscularly, and one day later the rabbits were sacrificed. The histological changes of the tissue surrounding the implant including the bone kinesics parameter were evaluated; the bone-implant interfaces were examined with scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. RESULT: Radiographic examinations showed that the bone recovery around the implant in the nano-Ti group was earlier compared to that in the Ti group. Histological examination suggested that the interface osseointegration rates 4, 8, and 12 weeks later of the nano-Ti groups were all significantly higher than those of the Ti group ( all P < 0.01). Strong tetracycline labeling and calcein labeling were observed around the implants in the nano-Ti group, indicating the active form action of new bone. The rates of bone mineralization and deposition 4, 8, and 12 weeks later of the nano-Ti group were higher than those of the Ti group. SEM and TEM examinations showed greater degradation of the surface and much more grains in cells in the HA group as compared to those in the nano-Ti group. The bone mineralization and osseointegration rates 4 weeks later of the HA group were significantly higher than those of the nano-Ti group (both P < 0.05), however, there were no significant differences in the bone mineralization and osseointegration rates 8 weeks later between these 2 groups. The bone mineralization and osseointegration rates 12 weeks later of the nano-Ti group were even higher than those of the HA group. CONCLUSION: The novel nanophase Ti6Al4V substrates improves the bone-implant osseointegration without significant grains of degradation in vivo, suggesting that the novel substrates and nano technology should be further considered for the orthopedic implant applications.