Additively manufactured Tantalum-titanium alloys with optimized osteogenic and immunomodulatory properties for load-bearing orthopedic implants

The Tantalum-Titanium (TaTi) alloys demonstrate significant potential as an orthopedic implant material. This study presents the development and comprehensive evaluation of novel additive manufactured TaTi alloys for orthopedic implant applications. Through a combination of materials engineering and biological validation, we designed pre-alloyed TaTi spherical powders with varying compositions (Ta25, Ta55, and Ta75) and fabricated dense and porous structures via selective laser melting (SLM). The SLM Ta55 alloy (Ti-55 wt %Ta) exhibited optimal mechanical properties, including a tensile strength of 891 MPa and an elastic modulus of 74 GPa, closely matching cortical bone. Surface characterization revealed that oxide layer (comprising Ta₂O₅/TiO₂) of SLM Ta55 promoted osteoblast adhesion and focal adhesion signaling activation. In vitro studies demonstrated superior osteogenic differentiation of MC3T3-E1 cells on SLM Ta55, evidenced by upregulated alkaline phosphatase (ALP) activity, mineralization, and osteogenic gene expression (ALP, Col-1, OCN, OPN). Transcriptomic analysis linked these effects to enhanced extracellular matrix remodeling and integrin-mediated mechanotransduction. Immunomodulatory assessments showed SLM Ta55 facilitated M2 macrophage polarization by suppressing JAK-STAT1 and TNF/NF-κB pro-inflammatory pathways while activating JAK3/STAT6, creating an anti-inflammatory microenvironment conducive to bone regeneration. In vivo rabbit femoral defect models confirmed SLM Ta55's exceptional osseointegration, with 37 % new bone area at 12 weeks, outperforming pure Ti and other TaTi alloys. Histological and immunofluorescence analyses validated reduced inflammation and increased osteocalcin expression around SLM Ta55 implants. This work establishes SLM Ta55 as a promising next-generation orthopedic biomaterial, synergizing mechanical compatibility, osteogenesis, and immunomodulation to advance personalized bone repair strategies.