Abstract: BACKGROUND: Neobavaisoflavone could promote bone formation and may be a potential small molecule drug for bone regeneration. The use of 3D printed bone tissue engineering scaffolds as drug delivery carriers for neobavaisoflavone is expected to enhance the potential application of bone regeneration.
OBJECTIVE: To explore the effects of polylactic acid/polydopamine/neobavaisoflavone bone scaffold on osteoclast and osteoblast activity. 
METHODS: (1) Fused deposition modeling technology was used to manufacture a 3D printed polylactic acid scaffold. These polylactic acid scaffolds were immersed in a dopamine solution containing or without neobavaisoflavone to produce polylactic acid/polydopamine/neobavaisoflavone scaffolds and polylactic acid/polydopamine scaffolds, respectively. The surface morphology, surface hardness, and compressive strength of the three groups of scaffolds were characterized, and the drug release properties of the polylactic acid/polydopamine/neobavaisoflavone scaffolds were investigated. (2) Mouse embryonic osteoblasts MC3T3-E1 were co-cultured with the three groups of scaffolds. The cytocompatibility of the scaffolds was assessed using CCK-8 assay and live-dead cell staining. The effects of the scaffolds on osteoblast migration were evaluated using Transwell assays. The effects of the scaffolds on osteoblast differentiation were assessed using alkaline phosphatase quantification and Alizarin red staining. RAW264.7 cells were co-cultured with the three groups of scaffolds. After osteoclast induction, the effects of the scaffolds on osteoclast differentiation were assessed by tartrate-resistant acid phosphatase staining. 
RESULTS AND CONCLUSION: (1) Scanning electron microscopy revealed that all three groups of scaffolds exhibited a three-dimensional structure with regularly interconnected porous structures, with an average pore size of 400 µm. The surface hardness and compressive strength of the polylactic acid/polydopamine scaffold and the polylactic acid/polydopamine/neobavaisoflavone scaffold were significantly higher than those of the polylactic acid scaffold (P < 0.05). The polylactic acid/polydopamine/neobavaisoflavone scaffold exhibited excellent drug release, with sustained drug release for over 14 days in vitro. (2) CCK-8 assay and live-dead cell staining demonstrated that all three groups of scaffolds exhibited good cytocompatibility. The polylactic acid/polydopamine scaffold and the polylactic acid/polydopamine/neobavaisoflavone scaffold promoted the proliferation of MC3T3-E1 cells. Transwell assay showed that compared with the polylactic acid scaffold, the polylactic acid/polydopamine scaffold and the polylactic acid/polydopamine/neobavaisoflavone scaffold promoted MC3T3-E1 cell migration. Alkaline phosphatase quantification assay and Alizarin red staining revealed that the polylactic acid/polydopamine scaffold and the polylactic acid/polydopamine/neobavaisoflavone scaffold promoted osteogenic differentiation of MC3T3-E1 cells compared with the other two scaffolds. Tartrate-resistant acid phosphate staining revealed that the polylactic acid/polydopamine/neobavaisoflavone scaffold inhibited osteoclast differentiation of RAW264.7 cells. (3) These results demonstrate that the polylactic acid/polydopamine/neobavaisoflavone scaffold has good biosafety and can promote bone regeneration by regulating osteoclast and osteoblast activity. 

Key words: 3D printed scaffold, polylactic acid, polydopamine, neobavaisoflavone, osteogenic differentiation, osteoclastic resorption, biomaterial