Effect Of Nanoporous Surface On Titanium Alloy To Rat Osteoblast

Objective: To evaluate the effect of nanophase Ti6Al4V alloy on the osteoblasts in vitro and osseointergration in vivo.Material and method: (1) The novel surface nanophase Ti6Al4V substrates were prepared according to the severe plastic deformation principle. (2) In the vitro study, the primary cultured osteoblasts of neonatal rat calvaria were cultured on the nanophase and the as-received Ti6Al4V substrates. Then the adhesion, proliferation, differentiation and mineralization of osteoblasts were evaluated by cells counting, scanning electron micrography, standard MTT assay, activity of ALP and fluorescent labeling of calcium deposition. (3) In the vivo study, the as-received (smooth group), nanophase (nano group) and hydroxyapatite-coated (HA group) Ti6Al4V substrates were implanted at the trochanter of femurs in SD New Zealand white rabbits. The rabbits were sacrificed at 4, 8 and 12 weeks after operation, and labeled with tetracycline and calcein days prior to sacrifice。The radiographic examinations were taken before sacrifice and then the histological changes of the tissue surrounding the implant including the bone kinesics parameter were evaluated; meanwhile, bone-implant interfaces were examed with scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively.Result: (1) The results showed a greater number of cells on the nanophase Ti6Al4V than any other substrates (P<0.05). SEM observation showed early cellular extension on the nanophase surfaces compared to other substrates. The growth curve of osteobalst cells cultured on different surfaces had similar appearance; however, longer exponential phase of growth with higher peak of osteoblast cells was observed on nanophase Ti6Al4V. The more active ALP could be observed in the osteoblasts cultured on the nanophase compared to the smooth Ti6Al4V (P<0.05). In addition, after 14d of culture, a strongly significant size of calcified nodules on the nanophase Ti6Al4V could also be observed (P<0.05). (2) Radiographic examinations showed that the bone recovery around the implant in nano-Ti group was earlier compared to that in the as-received group. Histological examations suggested that interface osseointegration rates in nano groups were significantly higher than in Ti group (P<0.01); the strong tetracycline and calcein labeling were also observed around the implants in nano-Ti group,which indicated the active form action of new bone. The average rates of bone mineralization and deposition in nano-Ti group were also higher than in Ti group (P<0.05). SEM and TEM examnations showed greater degradation of the surface and much more grains in cells in HA group as compared to those in nano-Ti group.Conclusion: The novel nanophase Ti6Al4V substrates might improve the function of osteoblasts in vitro and the interface osseointergration in vivo, which suggested that the novel substrates and nano technology should be further considered for the orthopedic implant applications.