BONE, CONNECTIVE tissues, PROTEINS, and MICROMECHANICS
Abstract: Polycaprolactone (PCL) is a bioresorbable polymer with potential applications for bone and cartilage repair. In this work, porous PCL scaffolds were computationally designed and then fabricated via selective laser sintering (SLS), a rapid prototyping technique. The microstructure and mechanical properties of the fabricated scaffolds were assessed and compared to the designed porous architectures and computationally predicted properties. Scaffolds were then seeded with bone morphogenetic protein-7 (BMP-7) transduced fibroblasts and implanted subcutaneously to evaluate biological properties and to demonstrate tissue in-growth. The work done illustrates the ability to design and fabricate PCL scaffolds with porous architecture that have sufficient mechanical properties for bone tissue engineering applications using SLS. Compressive modulus and yield strength values ranged from 52 to 67MPa and 2.0 to 3.2Mpa, respectively, lying within the lower range of properties reported for human trabecular bone. Finite element analysis (FEA) results showed that mechanical properties of scaffold designs and of fabricated scaffolds can be computationally predicted. Histological evaluation and micro-computed tomography (μCT) analysis of implanted scaffolds showed that bone can be generated in vivo. Finally, to demonstrate the clinical application of this technology, we designed and fabricated a prototype mandibular condyle scaffold based on an actual pig condyle. The integration of scaffold computational design and free-form fabrication techniques presented here could prove highly useful for the construction of scaffolds that have anatomy specific exterior architecture derived from patient CT or MRI data and an interior porous architecture derived from computational design optimization. [Copyright &y& Elsevier]
Schuster, M., Turecek, C., Kaiser, B., Stampfl, J., Liska, R., and Varga, F.
Journal of Macromolecular Science: Pure & Applied Chemistry. May2007, Vol. 44 Issue 5, p547-557. 11p. 2 Black and White Photographs, 3 Diagrams, 4 Charts, 8 Graphs.
PHOTOPOLYMERIZATION, RAPID prototyping, PHOTOPOLYMERS, FUNCTIONAL groups, MONOMERS, POLYMERS, and BIOPOLYMERS
Important characteristics of bone replacement materials are to support the attachment, growth, and differentiation of osteogenic cells. A second important characteristic of the material is that it can be photopolymerized, which allows the material to be applied to rapid prototyping that enables us to fabricate scaffolds in nearly any shape and structure. In these investigations, reactivity and biocompatibility of different types of commercially available acrylates and photoinitiators were determined. Cell viability was related to the functional groups in the monomers present, e.g., oligoethyleneglycol, urethane-, hydroxy- or carboxy groups. It was found that polymers obtained from acrylates with urethane units, most dialkylacrylamide and especially trimethylolpropane triacrylate gave outstanding biocompatibility. Mechanical testing proved to have significantly better performance (stiffness, strength) than many known thermoplastic biopolymers. [ABSTRACT FROM AUTHOR]
TISSUE scaffolds, TISSUE engineering, FINITE element method, RAPID prototyping, MINIMAL surfaces, TISSUE mechanics, PERMEABILITY, and BONES
Abstract: Triply-periodic minimal surfaces are shown to be a more versatile source of biomorphic scaffold designs than currently reported in the tissue engineering literature. A scaffold architecture with sheetlike morphology based on minimal surfaces is discussed, with significant structural and mechanical advantages over conventional designs. These sheet solids are porous solids obtained by inflation of cubic minimal surfaces to sheets of finite thickness, as opposed to the conventional network solids where the minimal surface forms the solid/void interface. Using a finite-element approach, the mechanical stiffness of sheet solids is shown to exceed that of conventional network solids for a wide range of volume fractions and material parameters. We further discuss structure–property relationships for mechanical properties useful for custom-designed fabrication by rapid prototyping. Transport properties of the scaffolds are analyzed using Lattice-Boltzmann computations of the fluid permeability. The large number of different minimal surfaces, each of which can be realized as sheet or network solids and at different volume fractions, provides design flexibility essential for the optimization of competing design targets. [Copyright &y& Elsevier]
Zhang, Jiancheng, Huang, Da, Liu, Shuifeng, Dong, Xianming, Li, Yiheng, Zhang, Hongwu, Yang, Zijun, Su, Qisheng, Huang, Wenhua, Zheng, Wenxu, and Zhou, Wuyi
Materials Science & Engineering: C. Dec2019, Vol. 105, pN.PAG-N.PAG. 1p.
THREE-dimensional printing, TISSUE engineering, ZIRCONIUM oxide, HYDROXYAPATITE, RAPID prototyping, BONE products, CASTOR oil, and BENDING strength
The construction of ceramic components with UV curing is a developing trend by an additive manufacturing (AM) technology, due to the excellent advantages of high precision selective fixation and rapid prototyping, the application of this technology to bone defect repair had become one of the hotspots of research. Hydroxyapatite (HAP) is one of the most popular calcium phosphate biomaterials, which is very close to the main ingredient of human bones. Thus, hydroxyapatite biomaterials are popular as bone graft materials. In summary, the preparation of HAP bioceramics by a 3D printing of digital light processing (DLP) is a promising work. However, the preparation of HAP hybrid suspensions with high solid loading and good fluidity that can be printed by DLP encountered some challenges. Therefore, the purpose of this work is to improve and develop a novel UV-curing suspension with a high solids loading, which the suspension with the hydrodynamic properties and stability are suitable for DLP printer, in order to compensate for the brittleness of HAP ceramics itself to a certain extent, a low amount of zirconia was added in the suspension as an additive to fabricate a zirconia toughened HAP bioceramic composite by a DLP of 3D printing. In this work, the HAP powder was pre-modified by two organic modifiers to improve the compatibility in the acrylic resin system, and the addition of the castor oil phosphate further reduced the shear stress of the suspension to ensure strong liquidity. The UV suspension with 60 wt% powder particle loading had a minimum viscosity of 7495 mPa·s at 30 rpm, which was vacuum sintered at 1100 °C, 1200 °C, and 1250 °C, respectively. The composite ceramics (with 6 wt% ZrO 2) at 1200 °C had a relative density of 90.7%, while the sintered samples at 1250 °C had stronger tensile strength and bending strength. The toughening effect of zirconia incorporation on HAP ceramics was also confirmed by the change of tensile modulus and bending modulus, whereas the corresponding mechanical properties were also significantly enhanced. • Surface modification of HAP nanoparticles was carried out to reduce the viscosity of ceramic suspension. • Ceramic green bodies were fabricated rapidly by additive manufacturing technology of digital light processing (DLP). • The addition of ZrO 2 had reduced the phase transformation decomposition of HAP during sintering process. [ABSTRACT FROM AUTHOR]