Additive manufacturing of an elastic poly(ester)urethane for cartilage tissue engineering

Although a growing knowledge on the field of tissue engineering of articular cartilage exists, reconstruction or in-vitro growth of functional hyaline tissue still represents an unmet challenge. Despite the simplicity of the tissue in terms of cell population and absence of innervation and vascularization, the outstanding mechanical properties of articular cartilage, which are the result of the specificity of its extra cellular matrix (ECM), are difficult to mimic. Most importantly, controlling the differentiation state or phenotype of chondrocytes, which are responsible of the deposition of this specialized ECM. represents a milestone in the regeneration of native articular cartilage. In this study, we fabricated fused deposition modelled (FDM) scaffolds with different pore sizes and architectures from an elastic and biodegradable poly(ester)urethane (PEU) with mechanical properties that can be modulated by design, and that ranged the elasticity of articular cartilage. Cell culture in additive manufactured 3D scaffolds exceeded the chondrogenic potential of the gold-standard pellet culture. In-vitro cell culture studies demonstrated the intrinsic potential of elastic (PEU) to drive the re-differentiation of de-differentiated chondrocytes when cultured in-vitro, in differentiation or basal media, better than pellet cultures. The formation of neo-tissue was assessed as a high deposition of GAGs and fibrillar collagen II, and a high expression of typical chondrogenic markers. Moreover, the collagen II / collagen I ratio commonly used to evaluate the differentiation state of chondrocytes (ratio > 1 being chondrocytes and, ratio <0 being de-differentiated chondrocytes) was higher than 5. Statement of significance Tissue engineering of articular cartilage requires material scaffolds capable of driving the deposition of a coherent and specific ECM representative of articular cartilage. Materials explored so far account for low mechanical properties (hydrogels), or are too stiff to mimic the elasticity of the native tissue (traditional polyesters). Here, we fabricated 3D fibrous scaffolds via FDM with a biodegradable poly(ester)urethane. The compressive Young's modulus and elastic limit of the scaffolds can be tuned by designed, mimicking those of the native tissue. The designed scaffolds showed an intrinsic potential to drive the formation of a GAG and collagen II rich ECM, and to drive a stable chondrogenic cell phenotype. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Additive Manufactured Scaffolds for Bone Tissue Engineering: Physical Characterization of Thermoplastic Composites with Functional Fillers

Thermoplastic polymer–filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load-bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate)/poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamicin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (G″ > G′) for the studied composites, at empirically determined extrusion temperatures. Coupled rheological–thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally not only made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Finally, we show computational models to predict multimaterial scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.The work was supported by a Horizon 2020 Research and Innovation Programme grant from the European Union, called the FAST project (grant no. 685825, project website: http:// project-fast.eu). The authors acknowledge the support of the FAST project consortium for the various aspects of this wor

Ballistic resistant article, semi-finished product for and method of making a shell for a ballistic resistant article

The invention relates to a ballistic resistant article, such as a helmet (1), comprising a double curved shell (2) in turn comprising a stack (5) of layers (6) of an oriented anti-ballistic material, the layers (6) comprising one or more plies and having a plurality of cuts (7), the ends of which define a central polygon (8) and lobes (10) extending from the polygon (8). The stack (5) comprises at least rotationally staggered layers (6) and, for most successive layers (6), the orientation of the material in the or at least one of the plies is rotationally staggered relative to the orientation of the material in the or at least one of the plies of a successive layer (6) over an angle of 90° ± 30°

Correlating molecular and crystallization dynamics to macroscopic fusion and thermodynamic stability in fused deposition modeling; a model study on polylactides

To define molecular parameters for fused deposition modeling of mechanically integral polylactide parts, the effect of intrinsic local heat fluctuations on morphology and structure evolution is studied. Macroscopic fusion during melt deposition is governed by molecular dynamics of solidification and positively affected by low print speed, low molar mass. However, low molar mass and high L-enantiomeric purity induces melt crystallization during deposition, limiting interfacial molecular diffusion. By increasing molar mass crystallization during melt deposition is suppressed, establishing interfacial molecular diffusion and mechanically effective interfaces. Further structure evolution via cold crystallization is timed in successive annealing cycles. Adding more layers entails a progressive decrease (i) in heat transfer to the build plate and (ii) number of annealing cycles per layer, inducing variations in crystallinity and thus thermodynamic instability. Consequently, macroscopic mechanics and geometrical stability of fused deposition modeled polylactides are compromised by judiciously timed crystallization and process design. (C) 2018 Elsevier Ltd. All rights reserved

Ballistic resistant article, semi-finished product for and method of making a shell for a ballistic resistant article

The invention relates to a ballistic resistant article, such as a helmet (1), comprising a double curved shell in turn comprising a stack (5) of layers (6) of an oriented anti-ballistic material, the layers comprising one or more plies and having a plurality of cuts (7), the ends of which define a central polygon (8) and lobes (10) extending from the polygon. The stack comprises at least 10 rotationally staggered layers and, for most successive layers, the orientation of the material in the or at least one of the plies is rotationally staggered relative to the orientation of the material in the or at least one of the plies of a successive layer over an angle of 90° ± 30°