Study on the conformational transformation and biocompatibility of mixed valence MOFs as micro arc oxidation treated binder jetting printed titanium alloy implant coatings

Currently, Selective Laser Melted (SLM) titanium alloys can meet the demands of personalized medical devices, but their poor surface roughness results in suboptimal surface biocompatibility. A low cost, high-efficiency 3D printing method, binder jetting additive manufacturing (BJAM), effectively address this issue. Furthermore, the application of bioactive coating on the BJAM-ed titanium alloy implants can enhance their surface bioinertness. This study synthesized Mn-MOFs via a solvothermal method, and then investigated the effects of synthesis temperature on the morphology, structure, and cyto-toxicity of Mn-BTC. Finally, the Mn-BTC with the best biocompatibility were coated on the BJAM-ed TC4 implant. The results indicate that Mn 3+ was gradually reduced to Mn 2+ by the thermodynamic driving forces, prompting a morphological transition of Mn-BTC from asymmetric polyhedrons to uniform spheres. This valence-morphology synergy significantly reduces the cytotoxicity of Mn-BTC synthesized at 170 °C. Subsequently, the 170 °C-synthesized Mn-BTC was coated on the BJAM-TC4 titanium alloy implants via micro-arc oxidation (MAO) to fabricate a Mn-BTC/MAO-TC4 coating. This coating not only effectively improves the RGR (increase by 12.1 %) compared to BJAM-TC4 but also significantly promotes BMSC adhesion performance. This study unveils the structure-activity relationship between temperature and morphology in Mn-BTC, providing a novel strategy for the surface functionalization of BJAM titanium alloy implants. • Temperature-driven valence transition induces a morphological evolution in Mn-BTC from polyhedral to spherical. • Mn-BTC characterised by a low valence state and spherical structure demonstrated optimal biocompatibility. • The Mn-BTC/MAO composite coating enhanced the biocompatibility of binder jet printed TC4 titanium alloy.