[Preparation of nano BaTiO3@Au Schottky junction coatings on titanium implant and the influence on osteogenic properties of rat bone marrow stem cells].

Objective: To prepare a nano-barium titanate@gold Schottky junction (nano-BaTiO₃@Au) coating and investigate its effects on the adhesion, proliferation, and osteogenic differentiation of bone marrow stem cells (BMSCs), aiming to explore a titanium surface modification strategy with superior osteogenic activity. Methods: Pure titanium specimens served as the control group (Ti group). Titanium dioxide coatings were prepared on their surfaces via anodic oxidation. Nano-barium titanate (nBTO group) was further synthesized using the hydrothermal method. Gold nanoparticles were grown in situ on the nano-BaTiO₃ via high-temperature reduction of chloroauric acid using sodium citrate, yielding the nano-barium titanate@gold Schottky junction coating (nBTO@Au group). Surface morphology was observed by scanning electron microscopy (SEM). Elemental composition was analyzed using X-ray energy dispersive spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). Crystal structure was analyzed using X-ray diffraction (XRD) and Raman spectroscopy. Hydrophilicity was assessed via water contact angle measurement. Specimens were co-cultured with BMSCs to evaluate biocompatibility and osteogenic properties. Cell proliferation on days 1, 3, 5, and 7 was assessed using the cell counting kit-8 (CCK-8) assay. Cytotoxicity towards BMSCs was assessed using live/dead cell staining. Cell morphology and adhesion were observed using cytoskeleton staining. Alkaline phosphatase (ALP) expression in BMSCs after 7 days was quantified using an ALP activity assay and ALP staining. Extracellular matrix mineralization after 7 days was evaluated using alizarin red staining and quantification assay. Each experiment was performed using three specimens per group. Results: Scanning electron microscopy revealed that gold nanoparticles with the diameter of(14.838±0.718) nm, uniform in size and homogeneously distributed, were successfully grown in situ on the surface of the nBTO coating. EDS and XPS confirmed the presence of Ba, Ti, O, and Au elements in the nBTO@Au composite coating. XRD and Raman spectroscopy analysis indicated that the nanostructured barium titanate (nBTO) coating was synthesized via a hydrothermal method.Water contact angle measurements showed that the contact angle was 66.8°± 0.45° for the control group, 22.55°±0.42° for the nBTO group, and 26.78°±1.15° for the nBTO@Au group, indicating good hydrophilicity of both nBTO and nBTO@Au coatings. On day 1 and day 3 of culture, the cell proliferation in the nBTO group was significantly lower than that in the control group (P<0.05). In contrast, no significant differences were observed between the nBTO@Au group and either the control group or the nBTO group (all P>0.05). By day 5, the cell proliferation of nBTO@Au groups was significantly lower than that of the control group (P<0.05), and the cell proliferation of nBTO group was significantly lower than that of the control group and that of the nBTO@Au group (P<0.05). By day 7, there were no statistically significant differences in cell proliferation among all experimental groups (F=1.62, P>0.05).Live/dead cell staining demonstrated that the cell survival rate exceeded 90% in all groups, with normal morphology and few dead cells, indicating good biocompatibility of the nBTO@Au coating. Compared to the control group, both nBTO and nBTO@Au groups promoted cell adhesion and spreading, although no significant difference in cell morphology was noted between the two modified groups. ALP staining revealed a larger stained area and deeper coloration in the nBTO@Au group. Quantitative results showed that ALP activity in the nBTO@Au group was significantly higher than that in both the nBTO and control groups (P<0.05), and the nBTO group also exhibited significantly higher activity than the control group(P<0.05). Alizarin red staining indicated the deepest coloration in the nBTO@Au group, followed by the nBTO group, and the lightest in the control group. Quantitative analysis further confirmed that the amount of calcium nodule deposition in the nBTO@Au group was significantly greater than that in the other two groups (P<0.05), and the nBTO group also showed significantly more deposition than the control group(P<0.05). Conclusions: This study successfully prepared an nBTO@Au coating possessing good biocompatibility and enhanced osteogenic properties.