Stimulation of healing within a rabbit calvarial defect by a PCL/PLGA scaffold blended with TCP using solid freeform fabrication technology

The purpose of this study was to investigate the healing capacity within an 8-mm rabbit calvarial defect using a polycaprolactone (PCL)/poly(lactic-co-glycolic acid) (PLGA) scaffold blended with tri-calcium phosphate (TCP) that was constructed using solid freeform fabrication (SFF) technology. The PCL/PLGA/TCP scaffold showed a 37?% higher compressive strength and rougher surface than the PCL/PLGA scaffold. In animal experiments, new bone formation was analyzed using microcomputed tomography (micro-CT) and histological and histometric analyses. The PCL/PLGA/TCP groups had significantly greater neo-tissue areas as compared with the control groups at 4 and 8 weeks (P?<?0.05). The PCL/PLGA/TCP group had significantly greater bone density as compared with the control and PCL/PLGA groups at 4 and 8 weeks (P?<?0.005). The results of this study suggest that the PCL/PLGA/TCP scaffold fabricated using SFF technology is useful for recovering and enhancing new bone formation in bony defects in rabbits.     

Design and fabrication of a freeform prism array for 3D microscopy

Traditional microscopes have limitations in obtaining true 3D (three-dimensional) stereovision. Although some optical microscopes have been developed for 3D vision, many of them are complex, expensive, or limited to transparent samples. In this research, a freeform optical prism array was designed and fabricated to achieve 3D stereo imaging capability for microscope and machine vision applications. To form clear stereo images from multiple directions simultaneously, freeform optical surface design was applied to the prisms. In a ray tracing operation to determine the optical performance of the freeform prisms, Taylor series was used to calculate the surface shape. The virtual image spot diagrams were generated by using ray tracing methods for both the freeform prisms and the regular prisms. The results showed that all the light rays can be traced back to a single point for the freeform prism, and aberration was much smaller than that of the regular prism. The ray spots formed by the freeform prisms were adequate for image formation. Furthermore, the freeform prism array was fabricated by using a combined ultraprecision diamond turning and slow tool servo broaching process in a single, uninterrupted operation. The slow tool servo process ensured that the relative tolerance among prisms is guaranteed by the precision of the ultraprecision machine without the need for assembly. Finally 3D imaging tests were conducted to verify the freeform prism array's optical performance. The principle of the freeform prism array investigated in this research can be applied to microscopy, machine vision, robotic sensing, and many other areas.     

A casting based process to fabricate 3D alginate scaffolds and to investigate the influence of heat transfer on pore architecture during fabrication

The fabrication of 3-dimensional (3D) tissue scaffolds is a competitive approach to engineered tissues. An ideal tissue scaffold must be highly porous, biocompatible, biodegradable, easily processed and cost-effective, and have adequate mechanical properties. A casting based process has been developed in this study to fabricate 3D alginate tissue scaffolds. The alginate/calcium gluconate hydrogel was quenched in a glass mold and freeze dried to form a highly porous tissue scaffold whose tiny pores retain the shape of the ice crystals during quenching. Knowing that the water in the alginate hydrogel would form ice crystals if frozen and that different cooling conditions may dramatically influence the pore architecture, the speed and direction of the heat transfer in freeze drying hydrogel were examined with regard to pore size and orientation. The pore architecture at the different locations of the fabricated scaffolds was characterized using scanning electron microscopy. The fabricated scaffolds consist of pores that are highly interconnected, with a diameter about 200 µm (average diameter of a capillary) to permit blood vessel penetration. It also has been found that the pore size, orientation, and uniformity are significantly affected by the condition of heat transfer during freeze drying. Tailoring the pore architecture of the scaffolds is feasible by controlling heat transfer. This study provides an insight on pore architecture formation and control by altered process parameters.     

Maintaining cell depth viability: on the efficacy of a trimodal scaffold pore architecture and dynamic rotational culturing

Tissue-engineering scaffold-based strategies have suffered from limited cell depth viability when cultured in vitro with viable cells typically existing at the fluid-scaffold interface. This is primarily believed to be due to the lack of nutrient delivery into and waste removal from the inner regions of the scaffold construct. This work focused on the assessment of a hydroxyapatite multi-domain porous scaffold architecture (i.e. a scaffold providing a discrete domain for cell occupancy and a separate domain for nutrient delivery). It has been demonstrated that incorporating unidirectional channels into a porous scaffold material significantly enhanced initial cell seeding distribution, while maintaining relatively high seeding efficiencies. In vitro static culturing showed that providing a discrete domain for nutrient diffusion and metabolic waste removal is insufficient to enhance or maintain homogeneous cell viability throughout the entire scaffold depth during a 7-day culture period. In contrast, scaffolds subjected to dynamic rotational culturing maintained uniform cell viability throughout the scaffold depth with increasing culturing time and enhanced the extent of cell proliferation (~2–2.4-fold increase) compared to static culturing.     

Evaluation of cell proliferation and differentiation on a poly(propylene fumarate) 3D scaffold treated with functional peptides

Synthetic polymers were used to fabricate a three-dimensional (3D) porous scaffold of poly(propylene fumarate)/diethyl fumarate (PPF/DEF). PPF-based materials are good candidates for bone regeneration, because of their non-toxic, biodegradable byproducts, and excellent mechanical properties. However, they exhibit hydrophobic surface properties that have negative effects on cell adhesion. To change the surface properties of a PPF/DEF scaffold, the authors used three peptide modifications (RGD, cyclo RGD, and RGD-KRSR mixture) to the scaffold and tested the effects on MC3T3-E1 pre-osteoblast adhesion, proliferation, and differentiation. The results indicated that peptide modification (particularly the RGD-KRDR mixture) altered the hydrophobic surface properties of the PPF/DEF scaffold, and promoted cell adhesion. Thus, it was suggest that peptide modification is a useful method for changing the properties of the PPF/DEF scaffold surface and may be applicable in bone tissue engineering.     

Characterisation of 3D woven composite internal architecture and effect of compaction

Yarn waviness and resin rich regions play a major role in 3D woven composite mechanical properties and failure. A detailed study of two angle interlock 3D woven carbon fabrics has been carried out to characterise these architectural features and how they change under increasing levels of compaction. Computerised tomography (CT) X-ray scanning was used to capture the internal architecture of the fabrics. The study focussed on the out-of-plane crimp of the yarns and the size and shape of resin rich regions in consolidated panels. Results showed areas of high local crimp at weft/weaver interlace points. This was exacerbated at low levels of compaction but was eventually lowered under higher compaction levels. The appearance of resin channels was found to be heavily dependent on weave style, with large resin pockets appearing in weaver yarn planes which decreased significantly in size under compaction with distinctive changes in profile.     

Novel 3D scaffold with enhanced physical and cell response properties for bone tissue regeneration,fabricated by patterned electrospinning/electrospraying

Developing three dimensional scaffolds mimicking the nanoscale structure of native extracellular matrix is a key parameter in tissue regeneration. In this study, we aimed to introduce a novel 3D structures composed of nanofibers (NF) and micro particles (MP) and compare their efficiency with 2D nanofibrous scaffold. The conventional nanofibrous PCL scaffolds are 2D mats fabricated by the electrospinning technique, whereas the NF/MP and patterned NF/MP PCL scaffolds are three dimensional structures fabricated by a modified electrospinning/electrospraying technique. The mentioned method was carried out by varying the electrospinning solution parameters and use of a metal mesh as the collector. Detailed fabrication process and morphological properties of the fabricated structures is discussed and porosity, pore size and PBS solution absorption value of the prepared structures are reported. Compared with the 2D structure, 3D scaffolds possessed enhanced porosity and pore size which led to the significant increase in their water uptake capacity. In vitro cell experiments were carried out on the prepared structures by the use of MG-63 osteosarcoma cell line. The fabricated 3D structures offered significantly increased cell attachment, spread and diffusion which were confirmed by SEM analysis. In vitro cytocompatibility assessed by MTT colorimetric assay indicated a continuous cell proliferation over 21 days on the innovative 3D structure, while on 2D mat cell proliferation stopped at early time points. Enhanced osteogenic differentiation of the seeded MG-63 cells on 3D scaffold was confirmed by the remarkable ALP activity together with increased and accelerated calcium deposition on this structure compared to 2D mat. Massive and well distributed bone minerals formed on patterned 3D structure were shown by EDX analysis. In comparison between NF/MP quasi-3D and Patterned NF/MP 3D scaffolds, patterned structures proceeded in all of the above properties. As such, the innovative Patterned NF/MP 3D scaffold could be considered as a proper bone graft substitute for bone tissue regeneration.     

Development of a mini 3D cell culture system using well defined nickel grids for the investigation of cell scaffold interactions

A bioreactor system was developed using a series of fine mesh nickel grids as free standing scaffolds to investigate the behaviours of fibroblasts and keratinocytes in tissue culture. It was found that the mesh size of the suspended grids, but not of the grids that attached to tissue culture surface, had significant influences on cell behaviour and there was a maximum size for fibroblast to span within the defined culture period. Time lapse video microscopy demonstrated fibroblasts cultured on these grids initially migrated onto the struts but then worked together to fill in the voids between struts with a membranous sheet of tissue. In contrast keratinocytes barely migrated from the initial site of cell deposition and when they moved (to a modest extent) it was as an integrated sheet of cells. Similar results were observed when both types of cells were co-cultured in the system.     

3D cell growth and proliferation on a RGD functionalized nanofibrillar hydrogel based on a conformationally restricted residue containing dipeptide

Three-dimensional (3D) hydrogels incorporating a compendium of bioactive molecules can allow efficient proliferation and differentiation of cells and can thus act as successful tissue engineering scaffolds. Self-assembled peptide-based hydrogels can be worthy candidates for such applications as peptides are biocompatible, biodegradable and can be easily functionalized with desired moieties. Here, we report 3D growth and proliferation of mammalian cells (HeLa and L929) on a dipeptide hydrogel chemically functionalized with a pentapeptide containing Arg-Gly-Asp (RGD) motif. The method of functionalization is simple, direct and can be adapted to other functional moieties as well. The functionalized gel was noncytotoxic, exhibited enhanced cell growth promoting properties, and promoted 3D growth and proliferation of cells for almost 2 weeks, with simultaneous preservation of their metabolic activities. The presence of effective cell growth supporting properties in a simple and easy to functionalize dipeptide hydrogel is unique and makes it a promising candidate for tissue engineering and cell biological applications.     

Engineered articular cartilage: influence of the scaffold on cell phenotype and proliferation

Articular cartilage defects do not heal. Biodegradable scaffolds have been studied for cartilage engineering in order to implant autologous chondrocytes and help cartilage repair. We tested some new collagen matrices differing in collagen type, origin, structure and methods of extraction and purification, and compared the behavior of human chondrocytes cultured on them. Human chondrocytes were grown for three weeks on four different equine type I collagen matrices, one type I, III porcine collagen matrix and one porcine type II collagen matrix. After 21 days, samples were subjected to histochemical, immunohistochemical and histomorphometric analysis to study phenotype expression and cell adhesion. At 7, 14 and 21 days cell proliferation was studied by incorporation of [3H]-thymidine. Our data evidence that the collagen type influences cell morphology, adhesion and growth; indeed, cellularity and rate of proliferation were significantly higher and cells were rounder on the collagen II matrix than on either of the collagen I matrices. Among the collagen I matrices, we observed a great variability in terms of cell adhesion and proliferation. The present study allowed us to identify one type I collagen matrix and one type II collagen matrix that could be usefully employed as a scaffold for chondrocyte transplantation.     

基于面结构光的叶片三维重构技术研究

为提高叶片三维检测速度与相位解码过程中的准确性等,通过选择投射解码准确率高的格雷码编码策略的结构光,同时避免叶片表面涂显影剂与粘贴标定点的方法,进行基于面结构光的叶片三维重建技术研究。通过选择合理的实验设备,设计机械结构,搭建一种基于面结构光的三维视觉检测实验系统。对三维视觉检测实验系统的标定方法与重构算法进行理论研究,利用三维视觉检测实验系统完成叶片某一位置的三维重构实验,并获得叶片的离散点云数据;试验结果进一步论证所设计系统的可行性,可为后续叶片三维视觉检测实验系统的研究提供基础。     

虚拟光栅变频投影三维测量技术的研究

虚拟光栅变频投影三维测量技术采用多光束干涉条纹形成虚拟余弦光栅,将虚拟余弦光栅投影到被测物体上得到被物体形貌调制的变形虚拟光栅。通过调整多光束干涉的楔角改变虚拟光栅频率,将两幅不同频率的变形虚拟光栅经过光学接收系统成像在CCD像机上,对CCD像机记录的变频变形光栅图像进行综合处理从而获取被测物体的三位形貌。本文给出了这种测量技术的原理,实验结果表明,采用变频虚拟光栅投影三维形貌测量技术可以有效地解决三维测量中被测物体高度变化率过大引起相位展开困难的问题。     

基于图像处理的外螺纹三维模型重构

提出了一种基于多角度序列图像特征实现外螺纹的三维模型重建的方法。首先在旋转平台上采集多角度序列螺纹件图像,然后对每帧图像进行特征点提取,将序列图像的特征点进行三维变换和插值,最终生成三维模型。实验结果表明,此算法能精确高精度地实现外螺纹三维模型重构。     

Cell-laden microengineered pullulan methacrylate hydrogels promote cell proliferation and 3D cluster formation

The ability to encapsulate cells in three-dimensional (3D) environments is potentially of benefit for tissue engineering and regenerative medicine. In this paper, we introduce pullulan methacrylate (PulMA) as a promising hydrogel platform for creating cell-laden microscale tissues. The hydration and mechanical properties of PulMA were demonstrated to be tunable through modulation of the degree of methacrylation and gel concentration. Cells encapsulated in PulMA exhibited excellent viability. Interestingly, while cells did not elongate in PulMA hydrogels, cells proliferated and organized into clusters, the size of which could be controlled by the hydrogel composition. By mixing with gelatin methacrylate (GelMA), the biological properties of PulMA could be enhanced as demonstrated by cells readily attaching to, proliferating, and elongating within the PulMA/GelMA composite hydrogels. These data suggest that PulMA hydrogels could be useful for creating complex, cell-responsive microtissues, especially for applications that require controlled cell clustering and proliferation.     

Analysis and fabrication of corner cube array based on laser direct writing technology

A detailed analysis of corner cube array (CCA) structure is carried out using the commercially available ray-tracing software ZEMAX. The retroreflective properties of CCA for short-range and long-range propagation are compared. An improved CCA structure with a relatively low structural depth (compared with rectangular CCA) is designed and analyzed. Higher retroreflectance (compared with triangular CCA) at a specific incident angle is proved by ray tracing. Two kinds of CCA structures, including the improved CCA, have been fabricated using laser direct writing technology. The fabrication results are qualified by three-dimensional shape measurement and ray tracing.     

基于激光三维雕刻的CFRP多梯层挖补胶接接头加工技术研究

在航空飞行器的碳纤维复合材料(CFRP)结构件损伤修复时,挖补胶接技术是获得高性能的CFRP层合板接头的理想工艺.本文提出一种CFRP层合板的多梯层挖补胶接接头设计策略,设计了挖补胶接接头阴阳膜构建和分层切片激光三维雕刻扫描工艺代码生成算法,探索了CFRP梯层界面的激光烧蚀成型工艺规律和粘结性能改善机理,验证了胶接接头...     

Preparation of Intelligent Supramolecular Hydrogels and Its application as 3D culture scaffold of ovarian cancer cell

正Destination:to prepare intelligent suparmolecular hydrogel by mimicking the key features of extracellular matrices(ECM)and culture ovarian cancer cells in 3D mold,then investigate the influence of microenvironments on behavior of cells.Method:Through using the inclusion complexes interact between trans-azobenzene(or adaman-     

The influence of surface nanoroughness of electrospun PLGA nanofibrous scaffold on nerve cell adhesion and proliferation

Electrospun nanofibrous scaffolds in neural tissue engineering provide an alternative approach for neural regeneration. Since the topography of a surface affects the microscopic behaviour of material; the creation of nanoscale surface features, which mimic the natural roughness of live tissue, on polymer surfaces can promote an appropriate cell growth and proliferation. In this research, a unique PLGA nanofibrous structure was fabricated without any post-electrospinning treatment. Scaffolds were prepared in two general groups: cylindrical and ribbon-shaped electrospun fibres, with smooth and rough (porous and grooved) surfaces. The experiments about nerve cell culture have demonstrated that the nanoroughness of PLGA electrospun scaffolds can increase the cell growing rate to 50 % in comparison with smooth and conventional electrospun scaffolds. SEM and AFM images and MTT assay results have shown that the roughened cylindrical scaffolds enhance the nerve growth and proliferation compared to smooth and ribbon-shaped nanofibrous scaffolds. A linear interaction has been found between cell proliferation and surface features. This helps to approximate MTT assay results by roughness parameters.     

基于VIC-3D技术的沥青混合料界面力学特性实验研究

为研究沥青混合料开裂及裂缝发展规律,通过SBS改性沥青混合料半圆试件三点弯曲实验,基于数字图像相关技术,利用VIC-3D(video image correlate,3D)采集系统对试件从加载到破坏全过程进行图像采集,并利用VIC-3D软件计算得到试件在受弯拉过程中三维位移场、应变场的变化及变化速率,分析并得出裂缝出现及发展规律;利用扫描电子显微镜对开裂试件断口进行观察,结合位移场、应变场及其变化速率揭示了试件开裂及裂缝发展的机理。结果表明,利用水平方向应变随时间变化规律可探究裂缝的发展轨迹;沥青混合料的开裂和裂缝发展沿沥青砂浆与粗集料的界面区发生,且趋向于表面情况相对差的集料的界面区;裂缝发展速率与界面区的厚度有关,可根据界面区厚度的代表值预测裂缝发展速率。