Tightly anchoring bone-like coating on the surface of titanium implants with complex three-dimensional geometry through radical polymerization

Biological fixation of a Ti implant demonstrates significant advantages over conventional physical fixation. Modifying the surface of Ti implants with hydroxyapatite (HAp) coating has proven to be a promising strategy to enhance their bone integration capability in vivo. The currently reported strategies are confronted with the following problems: (i) low interfacial bonding strength and poor structural stability under mechanical force; (ii) being incapable of encapsulating Ti implants with complex 3D geometry; (iii) complicated processing procedures and high processing costs. Here, we fabricated a bone-like polyacrylamide/poly(vinyl alcohol)/HAp (PAAm/PVA/HAp) coating on the surface of Ti implants with complex 3D geometry through thermal induced in situ radical polymerization of pre-adhered vicious acrylamide/PVA/HAp (AAm/PVA/HAp) emulsion. Covalent interaction between the Ti matrix and the coating was constructed through incorporating vinyl groups on the surface of Ti matrix using 3-(trimethoxysilyl)propyl methacrylate (TMSPMA). The as-prepared coating demonstrated a record high shear bonding strength of 144.5 MPa and 75.50 MPa in dry and moist states, respectively. In addition, its interfacial toughness reached to 1.27 kJ/m(2), while its maximum motion under shear mechanical force was only 0.64 mm (moist state). Anti-fatigue tests (approximate 100% toughness retention rate at displacement of 0.1 mm) and degradation experiment exhibited the long-term mechanical/structural stability of the coating in a in vivo environment. BMSCs co-culture assay demonstrated the superior cytocompatibility and osteogenic property of the coating. In sum, this work provided a simple and cost-effective strategy to construct homogeneous and tightly anchored HAp coating on the surface of Ti implants with complex 3D geometry.