The effects of surface treatments on electron beam melted Ti-6Al-4V disks on osteogenesis of human mesenchymal stromal cells.

Additive manufactured (AM) Titanium-6Aluminum-4Vanadium (Ti64) scaffolds display unique mechanical and biological properties for implant devices. The elastic modulus can be tailored by adjusting the porosity, further facilitating bone ingrowth. Although Ti64 implants are biocompatible, the effects of AM surfaces without porous structures, and how the topography and surface chemistry of the respective surfaces affect the osteogenesis of bone marrow-derived mesenchymal stromal cells (BMSCs) has not yet been revealed. In this paper, we cultured BMSCs on solid electron beam melted Ti64 disks subjected to three surface treatments: chemical etching (HF), atomic-layer deposition of TiO2 (TiO2), and polished (POL), or left untreated (AB). The biocompatibility and osteogenic properties of these surfaces were investigated, and the results were compared to cells cultured in regular tissue-culture polystyrene culturing wells (TCPS). The surfaces were hydrophobic, except for the polished surface which was hydrophilic. All surface treatments are biocompatible and allow for osteogenic differentiation, as revealed by viability assays and gene expression analysis. Scanning electron microscopy shows that cells adhere differently depending on the surface properties, with more filopodia on the rougher surfaces, AB and TiO2 disks, and more lamellipodia on the smoother surfaces, HF and POL disks. All groups stimulated with beta glycerophosphate, ascorbic acid, and dexamethasone, have elevated expression of genes related to matrix formation, where the cells cultured on the disks treated with TiO2, HF and POL have the overall highest expression. The AB group appears to be less favorable in regards to matrix formation. Considering the matrix mineralization, the rougher surfaces, AB and TiO2, are able to induce matrix mineralization, with an elevated gene expression of vitamin D receptors and calcium deposition of unstimulated cells. Finally, imaging at day 21 revealed an even amount of cells and matrix, covering most of the partially melted particles. Our results suggests that surface topography is more important to osteogenesis than the wettability of the surface. Overall, the present study contributes to the understanding of using surface modifications to AM Ti64 implant materials and reveals how they affect bone growth.

Revealing the influence of electron beam melted Ti-6Al-4V scaffolds on osteogenesis of human bone marrow-derived mesenchymal stromal cells.

Porous Titanium-6Aluminum-4Vanadium scaffolds made by electron beam-based additive manufacturing (AM) have emerged as state-of-the-art implant devices. However, there is still limited knowledge on how they influence the osteogenic differentiation of bone marrow-derived mesenchymal stromal cells (BMSCs). In this study, BMSCs are cultured on such porous scaffolds to determine how the scaffolds influence the osteogenic differentiation of the cells. The scaffolds are biocompatible, as revealed by the increasing cell viability. Cells are evenly distributed on the scaffolds after 3 days of culturing followed by an increase in bone matrix development after 21 days of culturing. qPCR analysis provides insight into the cells' osteogenic differentiation, where RUNX2 expression indicate the onset of differentiation towards osteoblasts. The COL1A1 expression suggests that the differentiated osteoblasts can produce the osteoid. Alkaline phosphatase staining indicates an onset of mineralization at day 7 in OM. The even deposits of calcium at day 21 further supports a successful bone mineralization. This work shines light on the interplay between AM Ti64 scaffolds and bone growth, which may ultimately lead to a new way of creating long lasting bone implants with fast recovery times.