Microstructural characterization and robust comparison of ceramic porous orbital implants

This research work tackles the challenge of developing an objective and reliable criterion to score porous bioceramic orbital implants with different microstructural characteristics. We produced porous glass-ceramics by the foam replica method and characterized their 3D micro-architecture through non-destructive X-ray micro-computed tomography. Six key features were estimated influencing their clinical performance, i.e. total porosity, pore interconnectivity, pore size distribution, surface-to-volume ratio, connectivity density and degree of anisotropy. Surface roughness was also characterized by profilometry. A multiparametric score accounting for all the estimated features was developed and used to evaluate the similarity between the produced porous bioceramics and commercial orbital implants. The clinical use of such a global score could make the selection of orbital implants less arbitrary and less dependent on the skills and personal experience of the ophthalmic surgeon. The approach presented in this study could be extended to other areas of ceramics science and technology.     

脚手架系统几何缺陷及节点刚度研究

介绍了脚手架系统几何缺陷的现场测量结果,包括柱子、框架的几何缺陷及荷载偏心。在浇筑混凝土前,测量现场脚手架系统的实际初始几何缺陷和荷载偏心。对随机抽取的构件进行试验,研究节点刚度,获得绕水平轴及竖轴的转角。对节点构造(双向、三向及四向节点)、弯曲轴、荷载方向进行试验。对数据进行统计分析,使其能应用于脚手架系统模拟和概率评估中。     

Internal architecture design and freeform fabrication of tissue replacement structures

Modeling, design and fabrication of tissue scaffolds with intricate architecture, porosity and pore size for desired tissue properties presents a challenge in tissue engineering. This paper will present the details of our development in the design and fabrication of the interior architecture of scaffolds using a novel design approach. The interior architecture design (IAD) approach seeks to generate layered scaffold freeform fabrication tool path without forming complicated 3D CAD scaffold models. This involves: applying the principle of layered manufacturing to determine the scaffold individual layered process planes and layered contours; defining the 2D characteristic patterns of the scaffold building blocks (unit cells) to form the Interior Scaffold Pattern; and the generating the process tool path for freeform fabrication of these scaffolds with the specified interior architecture. Feasibility studies applying the IAD algorithm to example models with multi-interior architecture and the generation of fabrication planning instructions will also be presented.     

Investigation of geometric imperfections and joint stiffness of support scaffold systems

This paper describes the findings from various site measurements of geometric imperfections of support scaffold systems, also known as falsework in industry. The measurements consist of out-of-straightness of the standards (uprights), out-of-plumb of the frame and loading eccentricity between the timber bearer and the U-head screw jack. The measurements were taken from different support scaffold construction sites before the pouring of concrete, representing actual initial geometric imperfections and loading eccentricity encountered in practice. The paper also reports the results of support scaffold joint tests. The tests were performed on randomly chosen used components to investigate the joint stiffness for rotations about vertical and horizontal axes. Tests were performed for various joint configurations (two-way, three-way, and four-way connections), bending axes, and loading directions. The statistical analysis of the data is presented in the paper for practical application in modelling and probabilistic assessment of support scaffold systems.     

A Review on the 3D Printing of Functional Structures for Medical Phantoms and Regenerated Tissue and Organ Applications

Medical models, or “phantoms,” have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional (3D) printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms (i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms) and 3D bio-printed structures (i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors) for regenerated tissues and organs.     

Growth of rat dorsal root ganglion neurons on a novel self-assembling scaffold containing IKVAV sequence

The potential benefits of self-assembly in synthesizing materials for the treatment of both peripheral and central nervous system disorders are tremendous. In this study, we synthesized peptide-amphiphile (PA) molecules containing IKVAV sequence and induced self-assembly of the PA solutions in vitro to form nanofiber gels. Then, we tested the characterization of gels by transmission electron microscopy and demonstrated the biocompatibility of this gel towards rat dorsal root ganglion neurons. The nanofiber gel was formed by self-assembly of IKVAV PA molecules, which was triggered by metal ions. The fibers were 7–8 nm in diameter and with lengths of hundreds of nanometers. Gels were shown to be non-toxic to neurons and able to promote neurons adhesion and neurite sprouting. The results indicated that the self-assembling scaffold containing IKVAV sequence had excellent biocompatibility with adult sensory neurons and could be useful in nerve tissue engineering.     

某外墙悬挑脚手架搭设与计算

结合某十二层教学楼施工提出的外墙脚手架搭设方案,对脚手架进行详细的阐述和强度计算。由于搭设方案合理,节约了设施和材料的一次性投入,保证了施工的连续性,产生了一定的经济效益。     

Biocompatibility of ceramic scaffolds for bone replacement made by 3D printing

Bone replacement materials used in tissue engineering require a high degree of safety and biological compatibility. For these reasons synthetic bone replacement materials based on calcium‐phosphates are being used more widely. To mimic natural bone, rapid prototyping processes and especially 3D printing are favourable. Using 3D printing, complex 3 dimensional structures can be made easily. In this study we successfully performed biocompatibility tests with a Hydroxyapatite test structure (HA‐S) made by 3D printing. Cytotoxicity tests were carried out according to DIN ISO 10993‐5 in static and dynamic cultivation setups. To estimate cell proliferation and analyze morphology, histological evaluation was done. In summary, good cell viability as well as good proliferation behaviour were found. Moreover, these results show that the 3D printing process in combination with the suitable material presented in this study is well suited for fabricating scaffolds for TE in the required accuracy and biological compatibility.     

A simple pathway in preparation of controlled porosity of biphasic calcium phosphate scaffold for dentin regeneration

A simple pathway in preparation of biphasic calcium phosphate scaffold of hydroxyapatite/beta-tricalcium phosphate with controlled pore size, shape and porosity using phosphoric acid and calcium carbonate was successfully developed. Microporosity was controlled by adjusting temperature and soaking time of the sintering process while macroporosity was obtained through addition of polyethylene spherical particles. The advantage of this method is that a highly pure biphasic calcium phosphate scaffold consisting of hydroxyapatite/beta-tricalcium phosphate in a controlled ratio of 20/80 with a mean pore size of 300 μm and 65% porosity can be produced. These properties of scaffold are of high potential for use in dentin regeneration.     

Bioactive Ceramic/Polyamide 6 Scaffold for Bone Regeneration: In vitro and in vivo Evaluation

A porous scaffold of bio-ceramic/polyamide 6 (PA 6) has been fabricated through a thermally induced phase separation technique. The scaffold was characterized by XPS, SEM and mechanical test. The results revealed that bio-ceramic/PA 6 scaffold had an interconnected porous structure with a porosity of about 78%. Moreover, bio-ceramic/PA 6 scaffolds were cultured with BMSCs to investigate their in vitro cytocompatibility, and they were implanted in subcutaneous sites of mice for 4 and 8 weeks to evaluate their in vivo histocompatibility. The result showed the composite scaffolds provided a favourable environment for initial cell adhesion, maintained cell viability and cell proliferation, and had good tissue compatibility.