Selective Laser Melting of Porous Nickel-Titanium As a Carrier for Human Mesenchymal Stem Cells

Nickel-titanium shape memory alloys (NiTi-SMA) are of biomedical interest due to an unusual range of pure elastic deformability with an elastic modulus closer to that of bone than any other metallic or ceramic material. Newly developed porous NiTi, produced by Selective Laser Melting (SLM) is currently analysed as carrier material for human mesenchymal stem cells (hMSC). SLM enables the production of highly complex and tailor-made implants for patients on the basis of CT data. Such implants could be used for the reconstruction of skull face or pelvis. HMSC are a promising cell type for regenerative medicine and tissue engineering due to their ability to support the regeneration of critical size bone defects. Loading of porous SLM-NiTi implants with autologous hMSC may enhance bone in growth and healing of critical bone defects. The purpose of the study was to assess whether porous SLM-NiTi is a suitable carrier for hMSC.

Therefore, specimens varying in porosity and orientation, were fabricated via SLM using two different laser beam diameters. HMSC were cultured for 8 days on those NiTi specimens. Cell viability was analysed using a two-colour fluorescence staining. Cell morphology and surface topography was analysed by scanning electron microscopy (SEM). Size and number of powder particles, released during cleaning of the specimens, were quantitatively analysed using a laser based particle analyzer.

Viable cells were detected on all specimens, after 8 d cell culture. Cell morphology and surface topology was dependent on the orientation of the specimens during SLM production. By reducing the diameter of the laser beam from 128 to 61 µm, the mean particle release could be decreased significantly. The SLM-NiTi samples are suitable carriers for hMSCs. Nevertheless, before carrying out in vivo studies the manufacturing process must be optimized in order to reduce the particle release.