Improved bone formation and ingrowth for additively manufactured porous Ti6Al4V bone implants with strontium laden nanotube array coating

Abstract

A Ti implant with an interconnected porous structure may be a better choice for bone defect restoration; an important issue is to improve its bone formation and ingrowth abilities. In this study, a porous Ti₆Al₄V implant is fabricated via electron beam melting (EBM) technology with a precisely controlled pore shape and size as well as good interconnectivity. Anodization treatment and further Sr incorporation give rise to an even distribution of the titania nanotube array (NT) and a strontium-laden NT (NTSr) coating on the outer and inner surface of the porous implant, which significantly enhance its hydrophilicity. The NT and NTSr coatings, especially NTSr, significantly improve the in vitro infiltration and osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) as well as the in vivo bone formation and ingrowth abilities of the porous implant. The data also show that the pore size differentially influences the biological effect of the porous implant, especially after surface modification. The smaller pores (600 μm) favor in vitro BMMSC proliferation and osteogenic differentiation and in vivo new bone mass formation, while the larger pores (800 μm) favor in vitro cell ingrowth and in vivo bone ingrowth. Our study suggests that the NTSr coating is very promising for porous implant applications to improve their biological performance and also uncover the differential effect of the pore size on the biological effect of the porous implant.