The search for materials with improved mechanical and biological properties is a major challenge in tissue engineering. This paper investigates, for the first time, the use of Polyethylene Terephthalate Glycol (PETG), a glycol-modified class of Polyethylene Terephthalate (PET), as a potential material for the fabrication of bone scaffolds. PETG scaffolds with a 0/90 lay-dawn pattern and different pore sizes (300, 350 and 450 µm) were produced using a filament-based extrusion additive manufacturing system and mechanically and biologically characterized. The performance of PETG scaffolds with 300 µm of pore size was compared with polycaprolactone (PCL). Results show that PETG scaffolds present significantly higher mechanical properties than PCL scaffolds, providing a biomechanical environment that promotes high cell attachment and proliferation.

This research investigates the accelerated hydrolytic degradation process of both anatomically designed bone scaffolds with a pore size gradient and a rectangular shape (biomimetically designed scaffolds or bone bricks). The effect of material composition is investigated considering poly-ε-caprolactone (PCL) as the main scaffold material, reinforced with ceramics such as hydroxyapatite (HA), β-tricalcium phosphate (TCP) and bioglass at a concentration of 20 wt%. In the case of rectangular scaffolds, the effect of pore size (200 μm, 300 μm and 500 μm) is also investigated. The degradation process (accelerated degradation) was investigated during a period of 5 days in a sodium hydroxide (NaOH) medium. Degraded bone bricks and rectangular scaffolds were measured each day to evaluate the weight loss of the samples, which were also morphologically, thermally, chemically and mechanically assessed. The results show that the PCL/bioglass bone brick scaffolds exhibited faster degradation kinetics in comparison with the PCL, PCL/HA and PCL/TCP bone bricks. Furthermore, the degradation kinetics of rectangular scaffolds increased by increasing the pore size from 500 μm to 200 μm. The results also indicate that, for the same material composition, bone bricks degrade slower compared with rectangular scaffolds. The scanning electron microscopy (SEM) images show that the degradation process was faster on the external regions of the bone brick scaffolds (600 μm pore size) compared with the internal regions (200 μm pore size). The thermal gravimetric analysis (TGA) results show that the ceramic concentration remained constant throughout the degradation process, while differential scanning calorimetry (DSC) results show that all scaffolds exhibited a reduction in crystallinity (Xc), enthalpy (Δm) and melting temperature (Tm) throughout the degradation process, while the glass transition temperature (Tg) slightly increased. Finally, the compression results show that the mechanical properties decreased during the degradation process, with PCL/bioglass bone bricks and rectangular scaffolds presenting higher mechanical properties with the same design in comparison with the other materials.

The use of biocompatible and biodegradable porous scaffolds produced via additive manufacturing is one of the most common approaches in tissue engineering. The geometric design of tissue engineering scaffolds (e.g., pore size, pore shape, and pore distribution) has a significant impact on their biological behavior. Fluid flow dynamics are important for understanding blood flow through a porous structure, as they determine the transport of nutrients and oxygen to cells and the flushing of toxic waste. The aim of this study is to investigate the impact of the scaffold architecture, pore size and distribution on its biological performance using Computational Fluid Dynamics (CFD). Different blood flow velocities (BFV) induce wall shear stresses (WSS) on cells. WSS values above 30 mPa are detrimental to their growth. In this study, two scaffold designs were considered: rectangular scaffolds with uniform square pores (300, 350, and 450 µm), and anatomically designed circular scaffolds with a bone-like structure and pore size gradient (476–979 µm). The anatomically designed scaffolds provided the best fluid flow conditions, suggesting a 24.21% improvement in the biological performance compared to the rectangular scaffolds. The numerical observations are aligned with those of previously reported biological studies.

Commercially available fixation plates are built using metallic biocompatible materials such as titanium and its alloys and stainless steel. However, these plates show a stiffness mismatch comparing to bone, leading to stress shielding and bone loss. In this paper, we investigate the combined use of topology optimisation and additive manufacturing to print fixation plates with reduced stiffness and improved biological performance. Ti-6Al-4 V plates were topology optimised considering different loading conditions and volume reductions and printed using electron beam melting and selective laser melting. The effect of processing conditions on the mechanical properties, microhardness, wear resistance and surface roughness was analysed. Results show acceptable wear resistance values for a medical device and a reduction of stress shielding by increasing volume reduction. It is also shown that no polishing is required as 3D printed plates are able to support cell attachment and proliferation. In comparison to commercial plates, 3D printed ones show significantly better biological performance. For the same design, SLM plates present higher mechanical properties, while EBM plates present better cell attachment and proliferation.

Ideal bone scaffolds for tissue engineering should be highly porous allowing cell attachment, spreading, and differentiation and presenting appropriate biomechanical properties. These antagonistic characteristics usually require extensive experimental work to achieve optimised balanced properties. This paper presents a simulation approach to determine the mechanical behaviour of bone scaffolds allowing the compressive modulus and the deformation mechanisms to be predicted. Polycaprolactone scaffolds with regular square pores and different porosities were considered. Scaffolds were also printed using an extrusion-based additive manufacturing and assessed under compressive loads. Similar designs were used for both simulation and fabrication steps. A good correlation between numerical and experimental results was obtained, highlighting the suitability of the simulation tool for the mechanical design of 3D-printed bone scaffolds.