In Vitro Evaluation of Pore Size Graded Bone Scaffolds with Different Material Composition.

The demand for biomimetic and biocompatible scaffolds in equivalence of structure and material composition for the regeneration of bone tissue is relevantly high. This article is investigating a novel three-dimensional (3D) printed porous structure called bone bricks with a gradient pore size mimicking the structure of the bone tissue. Poly-ɛ-caprolactone (PCL) combined with ceramics such as hydroxyapatite (HA), ß-tricalcium phosphate (TCP), and bioglass 45S5 were successfully mixed using a melt blending method and fabricated with the use of screw-assisted extrusion-based additive manufacturing system. Bone bricks containing the same material concentration (20 wt%) were biologically characterized through proliferation and differentiation tests. Scanning electron microscopy (SEM) was used to investigate the morphology of cells on the surface of bone bricks, whereas energy dispersive X-ray (EDX) spectroscopy was used to investigate the element composition on the surface of the bone bricks. Confocal imaging was used to investigate the number of differentiated cells on the surface of bone bricks. Proliferation results showed that bone bricks containing PCL/HA content are presenting higher proliferation properties, whereas differentiation results showed that bone bricks containing PCL/Bioglass 45S5 are presenting higher differentiation properties. Confocal imaging results showed that bone bricks containing PCL/Bioglass 45S5 are presenting a higher number of differentiated cells on their surface compared with the other material contents.

Accelerated Degradation of Poly-ε-caprolactone Composite Scaffolds for Large Bone Defects.

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), ß-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.

Bone Bricks: The Effect of Architecture and Material Composition on the Mechanical and Biological Performance of Bone Scaffolds.

Large bone loss injuries require high-performance scaffolds with an architecture and material composition resembling native bone. However, most bone scaffold studies focus on three-dimensional (3D) structures with simple rectangular or circular geometries and uniform pores, not able to recapitulate the geometric characteristics of the native tissue. This paper addresses this limitation by proposing novel anatomically designed scaffolds (bone bricks) with nonuniform pore dimensions (pore size gradients) designed based on new lay-dawn pattern strategies. The gradient design allows one to tailor the properties of the bricks and together with the incorporation of ceramic materials allows one to obtain structures with high mechanical properties (higher than reported in the literature for the same material composition) and improved biological characteristics.

Investigating the Influence of Architecture and Material Composition of 3D Printed Anatomical Design Scaffolds for Large Bone Defects.

There is a significant unmet clinical need to prevent amputations due to large bone loss injuries. We are addressing this problem by developing a novel, cost-effective osseointegrated prosthetic solution based on the use of modular pieces, bone bricks, made with biocompatible and biodegradable materials that fit together in a Lego-like way to form the prosthesis. This paper investigates the anatomical designed bone bricks with different architectures, pore size gradients, and material compositions. Polymer and polymer-composite 3D printed bone bricks are extensively morphological, mechanical, and biological characterized. Composite bone bricks were produced by mixing polycaprolactone (PCL) with different levels of hydroxyapatite (HA) and ß-tri-calcium phosphate (TCP). Results allowed to establish a correlation between bone bricks architecture and material composition and bone bricks performance. Reinforced bone bricks showed improved mechanical and biological results. Best mechanical properties were obtained with PCL/TCP bone bricks with 38 double zig-zag filaments and 14 spiral-like pattern filaments, while the best biological results were obtained with PCL/HA bone bricks based on 25 double zig-zag filaments and 14 spiral-like pattern filaments.