The osteogenic, inflammatory and osteo-immunomodulatory performances of biomedical Ti-Ta metal–metal composite with Ca- and Si-containing bioceramic coatings

It is known that good mechanical properties, low modulus to reduce stress-shielding effect, favorable osteogenic activity and limited inflammatory response are critical factors for orthopedic implants to induce excellent osteointegration. In this study, Ti-20% Ta metal-metal composite (referred as Ti-Ta) which consisted of Ti- and Ta-rich phases was fabricated via the strategy of powder metallurgy. Micro-arc oxidation (MAO) was employed to modify the surface of Ti-Ta composite. The surfaces of Ti-Ta composite after MAO treatment at an applied voltage of 250 (referred as MAO-250 V) or 300 V (referred as MAO-300 V) exhibited three distinct zones with significantly different morphological features and surface chemistry. Osteoblast-like SaOS-2 cells were found to be preferential to attach on the Ta-rich phase and its surrounding areas, exhibiting an area-dependent adhesion tendency. However, the attachment of Raw 264.7 macrophages was found to be insensitive to the surface characteristics. The proliferation and differentiation of SaOS-2 cells cultured on various surfaces basically followed the trend: MAO-modified surfaces > Ti-Ta surface > Ti surface. The Ti-Ta and MAO-modified surfaces were found to inhibit the inflammatory response and polarize macrophages to anti-inflammatory M2 phenotype compared to Ti surface. Moreover, the microenvironments created by Ti-Ta, MAO-250 V and MAO-300 V/macrophage interactions promoted the proliferation and differentiation of SaOS-2 cells compared to that created by Ti/macrophage interactions. MAO-300 V surface exhibited further enhanced positive osteo-immunomodulatory effects compared to Ti-Ta surface. Together, the Ti-20% Ta metal-metal composite modified by MAO at an applied voltage of 300 V is considered as a promising implant material for orthopedic applications.