Synergistic effect of Si-hydroxyapatite coating and VEGF adsorption on Ti6Al4V-ELI scaffolds for bone regeneration in an osteoporotic bone environment.

The osteogenic and angiogenic responses to metal macroporous scaffolds coated with silicon substituted hydroxyapatite (SiHA) and decorated with vascular endothelial growth factor (VEGF) have been evaluated in vitro and in vivo. Ti6Al4V-ELI scaffolds were prepared by electron beam melting and subsequently coated with Ca10(PO4)5.6(SiO4)0.4(OH)1.6 following a dip coating method. In vitro studies demonstrated that SiHA stimulates the proliferation of MC3T3-E1 pre-osteoblastic cells, whereas the adsorption of VEGF stimulates the proliferation of EC2 mature endothelial cells. In vivo studies were carried out in an osteoporotic sheep model, evidencing that only the simultaneous presence of both components led to a significant increase of new tissue formation in osteoporotic bone. STATEMENT OF SIGNIFICANCE: Reconstruction of bones after severe trauma or tumors extirpation is one of the most challenging tasks in the field of orthopedic surgery. This scenario is even more complicated in the case of osteoporotic patients, since their bone regeneration capability is decreased. In this work we present a porous implant that promotes bone regeneration even in osteoporotic bone. By coating the implant with osteogenic bioceramics such as silicon substituted hydroxyapatite and subsequent adsorption of vascular endothelial growth factor, these implants stimulate the bone ingrowth when they are implanted in osteoporotic sheep.

Compressive behaviour of gyroid lattice structures for human cancellous bone implant applications.

Electron beam melting (EBM) was used to fabricate porous titanium alloy structures. The elastic modulus of these porous structures was similar to the elastic modulus of the cancellous human bone. Two types of cellular lattice structures were manufactured and tested: gyroids and diamonds. The design of the gyroid structures was determined by the main angle of the struts with respect to the axial direction. Thus, structures with angles of between 19 and 68.5° were manufactured. The aim of the design was to reduce the amount of material needed to fabricate a structure with the desired angles to increase the range of stiffness of the scaffolds. Compression tests were conducted to obtain the elastic modulus and the strength. Both parameters increased as the angle decreased. Finally, the specific strength of the gyroid structures was compared with that of the diamond structures and other types of structures. It is shown that, for angles lower than 35°, the gyroid structures had a high strength to weight ratios.

Surface zwitterionization of customized 3D Ti6Al4V scaffolds: a promising alternative to eradicate bone infection.

Large and critical bone defect reconstruction is still a hard challenge in tumor resections, non-unions, some traumatisms and articular prosthesis revisions. The application of electron beam melting technology (EBM) to implant manufacturing constitutes a promising alternative, which provides better biomechanics and customized solutions. Implant infections are one of the most serious complications associated with surgical treatments, which require immediate solutions for achieving better clinical results. Herein, to confer antimicrobial properties, a simple and cost-effective approach based on a bifunctionalization process to create a zwitterionic surface on Ti6Al4V EBM implants is proposed. The obtained results show a notable reduction of bacterial adhesion (more than 97%) and total inhibition of biofilm formation, combined with demonstrated biocompatibility and bioactivity, permitting cell adhesion on the entire surface of these 3D zwitterionic scaffolds. This surface zwitterionization provides new perspectives for custom-made Ti6Al4V EBM implants for bone tissue regeneration with antimicrobial properties.

Computational study and experimental validation of porous structures fabricated by electron beam melting: a challenge to avoid stress shielding.

In this paper, several diamond non-stochastic lattice structures, fabricated by electron beam melting, were mechanically characterized by compression tests. A finite element model of the structures was developed, obtaining an equation that estimates the elastic modulus of the lattice structure. Finally, the differences between the numerical and the experimental results were analyzed and discussed.