Osteoblast viability on hydroxyapatite with well-adjusted submicron and micron surface roughness as monitored by the proliferation reagent WST-1

The impact of the cell surface roughness on titanium alloys used for biomedical implants has been extensively studied, whereas the dependency of human osteoblast viability on hydroxyapatite (HA) submicron and micron surface roughness has hitherto not yet been investigated in detail. Therefore, we investigate in this study the effect of HA substrates with different well-adjusted surface roughness on human osteoblast proliferation using the standard colorimetric reagent WST-1. By grinding, we obtained HA surfaces with six levels of well-defined surface roughness ranging from Sa = 3.36 µm down to 0.13 µm, resulting in hydrophilic contact angles from 11° to 27°. Energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray fluorescence measurements confirmed that neither grinding paper residues nor changes of the crystal structure were introduced to the HA substrates by the grinding process. By applying this simple surface treatment, we were able to isolate other effects from surface chemistry, crystal structure, and relative density. The changes of the osteoblast proliferation (WST-1 assay) on these different roughened HA surfaces after 7 days were found to be insignificant (p > 0.05), evaluated by one-way analysis of variance and Tuckey’s Multiple Comparison Method. The results of this study show that all roughened HA surfaces, regardless of the microtopography, are biocompatible and allow osteoblast attachment, proliferation, and collagen type I production. The comparison with surface roughness used for standard Ti-based implants yielded that for HA no finishing process is necessary to ensure a sound human osteoblast cell proliferation in vitro.