Comparison of Three Microstructure Fabrication Methods for Bone Cell Growth Studies

Different micropatterning techniques were applied to elucidate the potential for cell proliferation studies on calcium phosphate surfaces. Sintered hydroxyapatite (HA) platelets were microstructured by three different techniques: Aerosol jet printing (M³D^®), laser ablation and microcontact printing via polydimethylsiloxane (PDMS) stamps. The microstructures were designed as channels between 1000 and 3000 micron in length, 10 to 220 micron in width and 5 to 110 micron in height. An optical profilometer, a Scanning Electron Microscope (SEM) and X-ray diffraction were used to characterize the microstructures. Cell proliferation tests were carried out by incubating the microstructured ceramic samples in complete cell media for a maximum of seven days. Osteoblast-like cells (MG-63) were used for testing. Each sample was immersed in media in which the cells were already seeded. Imaging was performed by SEM and Fluorescence Microscopy. The cells proliferated on all three differently fabricated microstructures. Cell growth was observed in the microchannels as well as on the microchannel walls or spacers. In particular it turned out, that the microtopology can provoke the cells to elongate aligned to the direction of the microchannels. Non-directional growth was observed on non-structured areas. All three differently fabricated hydroxyapatite microstructuring methods seem to be attractive and promising techniques for use in bone cell growth studies. The applied fabrication techniques show many advantages for fundamental research in the field of cell interaction with ceramic microstructures and may exhibit possible methods of structuring implant surfaces.