Effect of micro-arc oxidation surface modification of 3D-printed porous titanium alloys on biological properties

Background: Three-dimensional (3D) printing technology has been widely used in orthopedics; however, it is still limited to the change of macroscopic structures. In order to further improve the biological properties of 3D-printed porous titanium scaffolds, this study introduced micro-arc oxidation (MAO) technology to modify the surface of porous titanium scaffolds and construct bioactive coatings on the surface of porous titanium scaffolds to improve the biocompatibility and osseointegration ability of the material. Methods: For in vitro experiments, human bone marrow stem cells (hBMSCs) were seeded onto untreated scaffolds (control group) and MAO-treated scaffolds (experimental group). After 24 h of co-culture, cytotoxicity was observed using live/dead staining, and cell/scaffold constructs were retrieved and processed for the assessment of cell morphology by using scanning electron microscopy (SEM). Cell proliferation was detected using the Cell Counting Kit-8 (CCK-8) assay after 3, 7, and 14 days of co-culture. The levels of alkaline phosphatase (ALP) in the cell supernatant were detected after 7 and 14 days of co-culture. For in vivo experiments, micro-computed tomography (micro-CT) and Masson Goldner's staining were used to evaluate bone ingrowth and osseointegration at 4 and 8 weeks postoperatively. Results: In vitro experiment results confirmed that the two groups of scaffolds were non-cytotoxic and the cell adhesion status on the MAO-treated scaffolds was better. Over time, cell proliferation and ALP levels were higher in the MAO-treated group than in the untreated scaffolds. In the in vivo experiments, the MAO-treated scaffolds showed better bone ingrowth and osseointegration than the untreated group at different time points. Conclusions: The MAO-treated porous titanium scaffold formed a uniform and dense bioactive coating on the surface, which was more conducive to cell adhesion, proliferation, and differentiation and showed better osseointegration and bone ingrowth in vivo.