Interaction between topography and coating in the formation of bone nodules in culture for hydroxyapatite- and titanium-coated micromachined surfaces

Abstract

Rat osteoblast cultures were maintained from 24 h to 6 weeks on hydroxyapatite (HA)- or titanium (Ti)-coated smooth and micromachined grooved substrata in medium supplemented with L-ascorbic acid-2-phosphate and beta-glycerophosphate to promote mineralization. The HA coatings, approximately 1 microm thick, were characterized using X-ray diffraction, surface roughness, and scanning electron microscopy (SEM). Osteoblasts elongated, aligned, and moved in the direction of the grooves on both Ti and HA grooved surfaces. HA surfaces produced significantly more bone-like nodules than Ti surfaces. All grooved substrata produced significantly more nodules than smooth surfaces. These results are consistent with the hypothesis that substrata can increase osteogenesis by formation of an appropriate microenvironment. There was also a statistically significant interaction between topography and chemistry in the formation of mineralized nodules. A strong correlation (r = 0.958) between alkaline phosphatase (Alk-P) at 2 weeks and nodule counts at 6 weeks was observed, suggesting that Alk-P may possibly be used as a leading indicator of osteogenesis on microfabricated surfaces. The results of this study indicate that surface topography and chemistry can affect osteogenesis, and that interactions between chemistry and topography can occur.

Bone integration capability of nanopolymorphic crystalline hydroxyapatite coated on titanium implants

“…The rapid bone formation implies that osteogenic cells may have differentiated faster on the surface, as reported in the literature on cell-HA interaction. 23,46,22 In addition, increased cell recruitment and attachment to HA-coated surfaces may enable rapid bone formation. 19,20 However, because of this promoted differentiation, the rate of proliferation may have been reduced, resulting in the formation of thin bone tissue and the reduced mass of periimplant bone.…”

“…Most of the commercially available and experimentally prepared HA-coated implants in the literature are sintered and show few microfeatures and no nanofeatures, although they often show supra-microscale roughness or irregularity. 18,46,22 In this study, HA nanocrystallites with 55% crystallinity and a Ca/P ratio of 1.66 were successfully created. The 55% crystallinity was within the range of the commercially available HA-coated implants, which varies from 44% to 96%.…”

“…For instance, it was reported that the effect of HA on osteoblasts varies depending on whether it is coated on smooth or grooved surfaces. 22 Most of the previous studies that tested the biological capability of HA used high-temperature-sintered HA; such HA does not seem to manifest the definable microscale or nanoscale surface morphology, but has not been morphologically characterized fully. 18,20,[23][24][25] Apatite coating with microsurface morphology can be deposited on material surfaces by biomimetic mineralization process using simulated body fluid.…”

Endoprothetischer Ersatz des oberen Sprunggelenks

“…Ein weiterer Nachteil der zementierten Fixation ist der exogene thermische Prozess beim Abbinden des Acrylates, der zu lokalen Weichteil-und knöchernen Hitzenekrosen führen kann. Hydroxylapatit-Coating ermöglicht molekulare Bindungen zwischen den Kristallen des Kalziumhydroxylapatits und dem knöchernen Bett [49,67]. Der Zeitraum für diesen Bindungsprozess erscheint kürzer (3-6 Wochen) im Vergleich zum Einwachsen bei Kugeln (Titan) [49].…”

“…Hydroxylapatit-Coating ermöglicht molekulare Bindungen zwischen den Kristallen des Kalziumhydroxylapatits und dem knöchernen Bett [49,67]. Der Zeitraum für diesen Bindungsprozess erscheint kürzer (3-6 Wochen) im Vergleich zum Einwachsen bei Kugeln (Titan) [49]. Demgegenüber wird Hydroxylapatit letztendlich komplett resorbiert [49], was hinsichtlich der Langzeitfixation bedenklich ist.…”