Orientation of human osteoblasts on hydroxyapatite-based microchannels

The effect of calcium phosphate-based microchannels on the growth and orientation of human osteoblast cells is investigated in this study. As substrates, hydroxyapatite-based microchannels with high contouring accuracy were fabricated by a novel micro-moulding technique. Microchannels obtained by this method featured widths ranging from 16.0±0.7 to 76.6±1.4μm and depths from 7.9±0.8 to 15.5±1.3μm. Surface and contour characterization was carried out using X-ray diffraction analysis, scanning electron microscopy imaging and 3D-confocal profilometry. Cell activity and alignment on microchannels with different widths were determined after 1 and 3days by photometric spectroscopy and fluorescence microscopic imaging and statistically analysed by Tukey’s multiple comparison test. On days 1 and 3 for microchannels of width 16 and 30μm, 70–80% of the osteoblasts oriented within an angular range of 0–15° relative to the microchannel direction. Interestingly, only 20% of the cells grew inside the microchannels for channel widths of 16 and 30μm. Substrates with channel widths of 45, 65 and 76μm allowed ∼40% of the cells to grow inside. The depth of the microchannel showed hardly any significant impact. All micropatterned surfaces provoked a good cell attachment, as flat and spread cell morphologies with lamellipodiae and filopodiae could already be observed after 1day. The effect of the microchannels on osteoblast activity was determined using the colorimetric WST-1 assay. In addition, the cell differentiation was assessed by collagen type I staining. The cell activity obtained by WST-1 assay differed insignificantly for all micropatterned samples of various widths and depths. The assessment of collagen type I yielded the same amounts for all micropatterned samples after 1, 3 and 7days. In summary, the microchannel width of HA-based patterns has a distinct effect on the directed growth of human osteoblast cells, allowing novel design strategies for surfaces such as dental implants.