Polycaprolactone/ß-Tricalcium Phosphate Composite Scaffolds with Advanced Pore Geometries Promote Human Mesenchymal Stromal Cells' Osteogenic Differentiation.

Critical-sized mandibular bone defects, arising from, for example, resections after tumor surgeries, are currently treated with autogenous bone grafts. This treatment is considered very invasive and is associated with limitations such as morbidity and graft resorption. Tissue engineering approaches propose to use 3D scaffolds that combine structural features, biomaterial properties, cells, and biomolecules to create biomimetic constructs. However, mimicking the complex anatomy and composition of the mandible poses a challenge in scaffold design. In our study, we evaluated the dual effect of complex pore geometry and material composition on the osteogenic potential of 3D printed scaffolds. The scaffolds were made of polycaprolactone (PCL) alone (TCP0), or with a high concentration of ß-tricalcium phosphate (ß-TCP) up to 40% w/w (TCP40), with two complex pore geometries, namely a star- (S) and a diamond-like (D) shape. Scanning electron microscopy and microcomputed tomography images confirmed high fidelity during the printing process. The D-scaffolds displayed higher compressive moduli than the corresponding S-scaffolds. TCP40 scaffolds in simulated body fluid showed deposition of minerals on the surface after 28 days. Subsequently, we assessed the differentiation of seeded bone marrow-derived human mesenchymal stromal cells (hMSCs) over 28 days. The early expression of RUNX2 in the cell nuclei confirmed the commitment toward an osteogenic phenotype. Moreover, alkaline phosphatase (ALP) activity and collagen deposition displayed an increasing trend in the D-scaffolds. Collagen type I was mainly present in the deposited extracellular matrix (ECM), confirming deposition of bone matrix. Finally, Alizarin Red staining showed successful mineralization on all the TCP40 samples, with higher values for the S-shaped scaffolds. Taken together, our study demonstrated that the complex pore architectures of scaffolds comprised TCP40 stimulated osteogenic differentiation and mineralization of hMSCs in vitro. Future research will aim to validate these findings in vivo.

Hypotrochoidal scaffolds for cartilage regeneration.

The main function of articular cartilage is to provide a low friction surface and protect the underlying subchondral bone. The extracellular matrix composition of articular cartilage mainly consists of glycosaminoglycans and collagen type II. Specifically, collagen type II fibers have an arch-like organization that can be mimicked with segments of a hypotrochoidal curve. In this study, a script was developed that allowed the fabrication of scaffolds with a hypotrochoidal design. This design was investigated and compared to a regular 0-90 woodpile design. The mechanical analyses revealed that the hypotrochoidal design had a lower component Young's modulus while the toughness and strain at yield were higher compared to the woodpile design. Fatigue tests showed that the hypotrochoidal design lost more energy per cycle due to the damping effect of the unique microarchitecture. In addition, data from cell culture under dynamic stimulation demonstrated that the collagen type II deposition was improved and collagen type X reduced in the hypotrochoidal design. Finally, Alcian blue staining revealed that the areas where the stress was higher during the stimulation produced more glycosaminoglycans. Our results highlight a new and simple scaffold design based on hypotrochoidal curves that could be used for cartilage tissue engineering.

Development of Biocomposite Alginate-Cuttlebone-Gelatin 3D Printing Inks Designed for Scaffolds with Bone Regeneration Potential.

Fabrication of three-dimensional (3D) scaffolds using natural biomaterials introduces valuable opportunities in bone tissue reconstruction and regeneration. The current study aimed at the development of paste-like 3D printing inks with an extracellular matrix-inspired formulation based on marine materials: sodium alginate (SA), cuttlebone (CB), and fish gelatin (FG). Macroporous scaffolds with microporous biocomposite filaments were obtained by 3D printing combined with post-printing crosslinking. CB fragments were used for their potential to stimulate biomineralization. Alginate enhanced CB embedding within the polymer matrix as confirmed by scanning electron microscopy (ESEM) and micro-computer tomography (micro-CT) and improved the deformation under controlled compression as revealed by micro-CT. SA addition resulted in a modulation of the bulk and surface mechanical behavior, and lead to more elongated cell morphology as imaged by confocal microscopy and ESEM after the adhesion of MC3T3-E1 preosteoblasts at 48 h. Formation of a new mineral phase was detected on the scaffold's surface after cell cultures. All the results were correlated with the scaffolds' compositions. Overall, the study reveals the potential of the marine materials-containing inks to deliver 3D scaffolds with potential for bone regeneration applications.

Comparative Thermo-Mechanical Properties of Sustainable Epoxy Polymer Networks Derived from Linseed Oil.

Considering its great industrial potential, epoxidized linseed oil (ELO) was crosslinked with different agents, both natural and synthetic: citric acid (CA, in the presence of water-W, or tetrahydrofuran-THF, as activator molecules) and Jeffamine D230, respectively, resulting bio-based polymeric matrices, studied further, comparatively, in terms of their properties, through different methods. Thermal curing parameters were established by means of Differential Scanning Calorimetry (DSC). Fourier transform Infrared Spectroscopy (FTIR) and DSC were used to identify the reactivity of each ELO-based formulation, discussing the influence of the employed curing systems under the conversion of the epoxy rings. Then, the obtained bio-based materials were characterized by different methods, establishing the structure-properties relation. Thermogravimetric analysis revealed higher thermal stability for the ELO_CA material when THF was used as an activator. Moreover, a higher glass transition temperature (Tg) with ~12 °C was registered for this material when compared with the one that resulted through the crosslinking of ELO with D230 conventional amine. Other important features, such as crosslink density, storage modulus, mechanical features, and water affinity, were discussed. Under the loop of a comprehensive approach, a set of remarkable properties were obtained for ELO_CA_THF material when compared with the one resulting from the crosslinking of ELO with the synthetic Jeffamine.

Controllable four axis extrusion-based additive manufacturing system for the fabrication of tubular scaffolds with tailorable mechanical properties.

Many tubular tissues such as blood vessels and trachea can suffer long-segmental defects through trauma and disease. With current limitations in the use of autologous grafts, the need for a synthetic substitute is of continuous interest as possible alternatives. Fabrication of these tubular organs is commonly done with techniques such as electrospinning and melt electrowriting using a rotational collector. Current additive manufacturing (AM) systems do not commonly implement the use of a rotational axis, which limits their application for the fabrication of tubular scaffolds. In this study, a four axis extrusion-based AM system similar to fused deposition modeling (FDM) has been developed to create tubular hollow scaffolds. A rectangular and a diamond pore design were further investigated for mechanical characterization, as a standard and a biomimicry pore geometry respectively. We demonstrated that in the radial compression mode the diamond pore design had a higher Young's modulus (19,8 ± 0,7 MPa compared to 2,8 ± 0,5 MPa), while in the longitudinal tensile mode the rectangular pore design had a higher Young's modulus (5,8 ± 0,2 MPa compared to 0,1 ± 0,01 MPa). Three-point bending analyses revealed that the diamond pore design is more resistant to luminal collapse compared to the rectangular design. This data showed that by changing the scaffold pore design, a wide range of mechanical properties could be obtained. Furthermore, a full control over scaffold design and geometry can be achieved with the developed 4-axis extrusion-based system, which has not been reported with other techniques. This flexibility allow the manufacturing of scaffolds for diverse tubular tissue regeneration applications by designing suitable deposition patterns to match their mechanical pre-requisites.

Electrospun Fibre Webs Templated Synthesis of Mineral Scaffolds Based on Calcium Phosphates and Barium Titanate.

The current work focuses on the development of mineral scaffolds with complex composition and controlled morphology by using a polymeric template in the form of nonwoven fibre webs fabricated through electrospinning. By a cross-linking process, gelatine fibres stable in aqueous solutions were achieved, these being further subjected to a loading step with two types of mineral phases: calcium phosphates deposited by chemical reaction and barium titanate nanoparticles as decoration on the previously achieved structures. Thus, hybrid materials were obtained and subsequently processed in terms of freeze-drying and heat treating with the purpose of burning the template and consolidating the mineral part as potential bone implants with improved biological response by external stimulation. The results confirmed the tunable morphology, as well as the considerable applicability of both as-prepared and final samples for the development of medical devices, which encourages the continuation of research in the direction of assessing the synergistic contribution of barium titanate domains polarisation/magnetisation by external applied fields.