| Summary: | Osteogenesis was studied using rat bone cells cultured on
hydroxyapatite (HA) or titanium (Ti) coated smooth and grooved substrata.
Osteoblast cultures were maintained from 24hrs to 6 weeks in culture
medium and supplemented with L-ascorbic acid-2-phosphate and β-
glycerophosphate to promote mineralization. The HA coatings were
characterized using X-ray diffraction, surface roughness and scanning
electron microscopy (SEM). The ceramic hydroxyapatite coating, was
dense and uniform, containing HA crystals and was ≈ 1µm thick. Time-lapse
cinemicrography of osteoblasts locomotion on HA surfaces revealed
osteoblasts moved with the direction of the grooves, that is they
exhibited contact guidance. Scanning electron microscopic observations
revealed osteoblasts were elongated and orientated on both Ti and HA
grooved surfaces. Collagen fibers, as assessed by picro-sirius staining
and polarized light microscopy, were aligned on both HA and Ti grooved
surfaces. Although not quantified, it appeared that nodule formation was
greatest under culture conditions that produced aligned collagen.
Osteogenesis was measured by counts of tetracycline labelled bone-like
nodules and alkaline phosphatase activity. HA coated surfaces produced
significantly more mineralized nodules than Ti surfaces. Surfaces with
grooves and narrow gaps produced the highest number of nodules. All
grooved substrata produced significantly more nodules than smooth
surfaces. These results are consistent with the concept that substrata
that form a microenvironment by restricting diffusion increase bone-like
tissue production. A novel finding in this thesis was that there was a
statistically significant interaction between topography and chemistry in
the formation of mineralized nodules. An excellent correlation (r= 0.958)
between alkaline phosphatase at 2 weeks and nodule counts at 6 weeks
was observed, suggesting that Alk-P is a good leading indicator of
osteogenesis on microfabricated surfaces. Therefore Alk-P might be used
to screen surfaces for their nodule production, thus saving time and
expense. The results of this study indicated that topography and
chemistry can affect osteogenesis on biomaterials, and that interactions
between chemistry and topography can occur.
|
|---|
