Abstract
Titanium (Ti) and Ti alloys have been used for decades for bone prostheses due to its mechanical reliability and good biocompatibility. However, the high stiffness of Ti implants and the lack of bioactivity are pending issues that should be improved to minimize implant failure. The stress shielding effect, a result of the stiffness mismatch between titanium and bone, can be reduced by introducing a tailored structural porosity in the implant. In this work, porous titanium structures were produced by direct ink writing (DIW), using a new Ti ink formulation containing a thermosensitive hydrogel. A thermal treatment was optimized to ensure the complete elimination of the binder before the sintering process, in order to avoid contamination of the titanium structures. The samples were sintered in argon atmosphere at 1200 °C, 1300 °C or 1400 °C, resulting in total porosities ranging between 72.3% and 77.7%. A correlation was found between the total porosity and the elastic modulus of the scaffolds. The stiffness and yield strength were similar to those of cancellous bone. The functionalization of the scaffold surface with a cell adhesion fibronectin recombinant fragment resulted in enhanced adhesion and spreading of osteoblastic-like cells, together with increased alkaline phosphatase expression and mineralization.
Highlights
The rise in the life expectancy of the population is leading to an increasing need for musculoskeletal surgical procedures involving bone substitutes and bone implants [1]
At the end of the incubation time, samples were washed with phosphate-buffered solution (PBS) and the adhered cells were fixed with 4% v/v paraformaldehyde at room temperature (RT) for 20 min
The Ti powder used for this study consisted of irregular particles (Figure 1a), with a unimodal
Summary
The rise in the life expectancy of the population is leading to an increasing need for musculoskeletal surgical procedures involving bone substitutes and bone implants [1]. DIW is a low-cost technology that can be used to manufacture complex shapes with controlled geometries at the micrometer scale without wasting metal powder [16] This technique enables the fabrication of scaffolds by extruding a pseudoplastic ink through a nozzle until the required geometry is created. Once the inks were prepared, they were left in a fume hood in order to eliminate the excess of DCM and to adjust the viscosity to 30–35 Pa·s, a step which can take several hours, and required a sintering process in a reducing atmosphere Another approach was proposed by Li et al, where Ti6Al4V powders were mixed with an aqueous solution of methylcellulose and stearic acid as a binder [23]. A new formulation of printable titanium paste using Pluronic F-127® as a binder is proposed and optimized to obtain
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