ABSTRACT
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±1.4 µm and depths from 7.9±0.8 to 15.5±1.3 µm. 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 3 days 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 30 µm, 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 30 µm. Substrates with channel widths of 45, 65 and 76 µm allowed â¼40% 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 1 day. 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 7 days. 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.
