3D gel-printing of hierarchically porous BCP scaffolds for bone tissue engineering

In this study, a conventional technique of porous preparation was used to improve the constructive capability of direct ink writing on microstructures, and the hierarchically porous scaffolds were successfully prepared by 3D gel printing (3DGP). Micron-sized hydroxyapatite (HA) was coated with tricalcium phosphate (TCP) nanopowders synthesized by chemical co-precipitation to form biphasic calcium phosphate (BCP). The random structure of concave micropores was achieved by filling the BCP slurry with PMMA microspheres while successfully controlling the internal porosity of printed filaments. The results showed that the three-stage porous structure was successfully constructed, i.e., macroscopic pores of 1.50–2.00 mm, spherical micropores of 100–200 µm, and inter-powder interstices of 1.00–10.00 µm. Nano-TCP coated micron-HA powders improved the sintering activity of BCP particles. The compressive strength and porosity of the scaffolds sintered at 1400 °C were 2.78 MPa and 84.98%. The hierarchically porous BCP scaffolds had bright applications in bone tissue engineering.     

Effect of different CaSO4 contents on CaSiO3-CaSO4 porous composite bone scaffolds by 3D gel-printing

Porous CaSiO₃-CaSO₄ composite scaffolds were successfully prepared by 3D gel-printing (3DGP) technology in this study. In order to further improve the degradation performance of pure CaSiO₃ scaffolds, the effect of different CaSO₄ doping contents on CaSiO₃-CaSO₄ composite scaffolds was studied. The results show that when the porous composite scaffolds were placed in simulated body fluid (SBF) for 5 weeks, the weight loss rate was 2.41% (CaSiO₃-1%CaSO₄), 3.97% (CaSiO₃-3%CaSO₄), 4.18% (CaSiO₃-5%CaSO₄), 6.87% (CaSiO₃-7%CaSO₄), and 12.93% (CaSiO₃-9%CaSO₄), respectively, which could be concluded that CaSO₄ doping has a significant effect on improving the biodegradability of CaSiO₃ scaffolds. And CaSO₄ doping can also effectively improve the compressive strength of composite scaffolds and that of CaSiO₃-3%CaSO₄ composite scaffolds was tested as 54.67 MPa, and the shrinkage rate of porous composite scaffolds was nearly 11.4%, which meets the application requirements of bone repairing engineering.     

3D printing of porous scaffolds BaTiO3 piezoelectric ceramics and regulation of their mechanical and electrical properties

A series of porous scaffolds of piezoelectric ceramic barium titanate (BaTiO₃) were successfully fabricated by Digital Light Processing (DLP) 3D printing technology in this work. To obtain a high-precision and high-purity sample, the debinding sintering profile was explored and the optimal parameters were determined as 1425 °C for 2h. With the increase of scaffolds porosity from 10% to 90%, the compressive strength and piezoelectric coefficient (d₃₃) decreased gradually. The empirical formulas about the mechanical and piezoelectric properties were obtained by adjusting BaTiO₃ ceramics with different porosity. In addition, the distribution of potential and stress under 100 MPa pressure were studied by the finite element method (FEM).     

Effect of SiO2 in situ cross-linked CS/PVA on SrFe12O19 scaffolds prepared by 3D gel printing for targeting

The design of magnetic composite scaffolds with superior properties has the potential to construct a targeted delivery platform with hyperthermia. In this study, strontium hexaferrite (SrFe₁₂O₁₉, SrM) magnetic nanoparticles (MNPs) were obtained by the chemical precipitation method. Non-toxic cross-linked biogels were prepared for adhesive ceramic scaffolds, and chitosan/polyvinylalcohol (CS/PVA)-bonded SrM magnetic nanoscaffolds were successfully prepared by 3D gel printing (3DGP) method. The effects of PVA physical cross-linking and in situ formed SiO₂ on the properties of CS-bonded scaffolds were evaluated, and the compressive strengths were increased from 6.13 ± 2.45 MPa to 8.80 ± 2.02 MPa and 17.18 ± 2.15 MPa, respectively. The results showed that the saturation magnetization of SiO₂/CS/PVA/SrM composite scaffolds was 59.96 emu/g. In vitro immersion experiments showed that the degradation rates of SiO₂/CS/PVA/SrM scaffolds were 4.90% after 28 days, and the in situ SiO₂ improved the deposition of calcium salts on the scaffolds. The experiments showed that the SrM magnetic scaffolds could not only concentrate magnetic fields to improve the efficiency of targeting deposition but also achieve a weak targeting process without external magnetic field assistance. In vitro cell proliferation test showed that MC3T3-E1 cells had good adhesion and proliferation on the surface of SiO₂/CS/PVA/SrM scaffolds, which indicated that the scaffolds may be used for bone repairing.     

Synthesis and incorporation of rod-like nano-hydroxyapatite into type I collagen matrix: A hybrid formulation for 3D printing of bone scaffolds

Over the recent years, nanometric hydroxyapatite (HA) has gained interest as constituent of hybrid systems for bone scaffold fabrication, due to its biomimicry and biocompatibility. In this study, rod-like nano-HA particles were introduced in a type I collagen matrix to create a composite mimicking the bone composition. HA nano-rods (40−60 nm × 20 nm) were synthesised by hydrothermal method involving the use of an ammonium-based dispersing agent (Darvan 821-A) and fully characterised. The homogeneous dispersion of HA nanoparticles throughout the final hybrid formulation was achieved through their suspension in a collagen solution in presence of Darvan 821-A. The resulting homogeneous collagen/nano-HA suspension proved to be suitable for extrusion printing applications, showing shear thinning and sol-gel transition upon simil-physiological conditions. Furthermore, mesh-like structures were printed in a gelatine-supporting bath by means of a commercial bioprinter further demonstrating the potential of the designed hybrid system for the fabrication of 3D bone-like scaffolds.     

Fabrication of forsterite scaffolds with photothermal-induced antibacterial activity by 3D printing and polymer-derived ceramics strategy

Bacterial infection of the implanting materials is one of the greatest challenges in bone tissue engineering. In this study, porous forsterite scaffolds with antibacterial activity have been fabricated by combining 3D printing and polymer-derived ceramics (PDCs) strategy, which effectively avoided the generation of MgSiO₃ and MgO impurities. Forsterite scaffolds sintered in an argon atmosphere can generate free carbon in the scaffolds, which exhibited excellent photothermal effect and could inhibit the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. In addition, forsterite scaffolds have uniform macroporous structure, high compressive strength (>30 MPa) and low degradation rate. Hence, forsterite scaffolds fabricated by combining 3D printing and PDCs strategy would be a promising candidate for bone tissue engineering.     

3D printing of bioactive macro/microporous continuous carbon fibre reinforced hydroxyapatite composite scaffolds with synchronously enhanced strength and toughness

Continuous carbon fibre (CF) reinforced HA (CF/HA) composite scaffolds were prepared using a self-designed and manufactured 3D printer. The optimised design of nozzle structure and the tailored viscoelastic property of HA inks ensured compound extrusion of monofilament and multifilament CF with HA rod. The composite scaffolds designed using the CAD programme and sintered via a suitable process exhibited a hierarchical macro/microporous structure and contained approximately 50% HA and 50% β-TCP. The continuous CF synchronously enhanced the strength and toughness of the scaffolds. The compressive strengths of 1CF/HA and 5CF/HA were 11.4 ± 1.7 MPa and 16.3 ± 2.6 MPa, respectively, which were approximately double and triple compared with that of HA scaffolds. The fracture toughness of 1CF/HA was approximately double that of HA scaffolds and close to that of cortical bone. In vitro and in vivo studies demonstrated that 1CF/HA also had apatite formation capability and adequate bone regeneration capacity.     

Bioactive and Biocompatible Macroporous Scaffolds with Tunable Performances Prepared Based on 3D Printing of the Pre‐Crosslinked Sodium Alginate/Hydroxyapatite Hydrogel Ink

Bioactive and biocompatible porous scaffold materials with adjustable pore structures and drug delivery capability are one of the key elements in bone tissue engineering. In this work, bioactive and biocompatible sodium alginate (SA)/hydroxyapatite (HAP) macroporous scaffolds are facilely and effectively fabricated based on 3D printing of the pre‐crosslinked SA/HAP hydrogels followed by further crosslinking to improve the mechanical properties of scaffolds. The pore structures and porosity (>80%) of the porous scaffolds can be readily tailored by varying the formation conditions. Furthermore, the in vitro biomineralization tests show that the bioactivity of the porous scaffolds is effectively enhanced by the addition of HAP nanoparticles into the scaffold matrix. Furthermore, the anti‐inflammatory drug curcumin is loaded into the porous scaffolds and the in vitro release study shows the sustainable drug release function of the porous scaffolds. Moreover, mouse bone mesenchymal stem cells (mBMSCs) are cultured on the porous scaffolds, and the results of the in vitro biocompatibility experiment show that the mBMSCs can be adhered well on the porous scaffolds. All of the results suggest that the bioactive and biocompatible SA/HAP porous scaffolds have great application potential in bone tissue engineering.     

维生素D_3对成骨细胞增殖和分化行为的影响

生理环境下的维生素D_3在骨质疏松的发病机制中发挥重要作用。目前,业界广泛研究的对象是维生素D_3对成骨细胞行为的影响作用。着重研究了维生素D_3对成骨细胞增殖和分化行为的影响。采用不同浓度的维生素D_3(0, 1, 10,100 nmmol/L)对成骨细胞进行刺激,观察维生素D_3对成骨细胞增殖和分化行为的影响。     

Effect of sodium carbonate addition on the properties of calcium silicate scaffolds fabricated by 3DIP

3D ink printing (3DIP) technology can accurately control the macroscopic size and microstructure of bioceramic scaffolds. However, nonceramic components in the printing ink used in 3DIP severely affect densification, resulting in less desirable mechanical properties of the scaffolds. In this study, a strategy of sintering assisted by a sintering aid (sodium carbonate) was used to prepare calcium silicate (CSi) scaffolds with high strength. The addition of 1% sintering aid to a CSi scaffold sintered at 1100 °C led to an appreciable compressive strength (47.8 MPa) and high elastic modulus (1847 MPa). Moreover, the CSi scaffolds with sintering aids showed better degradation ability and mineralization ability than the CSi scaffolds without sintering aids. It is expected that the method involving strengthening with sintering aids will promote the application of 3DIP bioceramic scaffolds in the repair of bone defects.     

The Effects of Tgfb1 and Csf3 on Chondrogenic Differentiation of iPS Cells in 2D and 3D Culture Environment

Mesenchymal stem (MS) cells, embryonic stem (ES) cells, and induced pluripotent stem (iPS) cells are known for their ability to differentiate into different lineages, including chondrocytes in culture. However, the existing protocol for chondrocyte differentiation is time consuming and labor intensive. To improve and simplify the differentiation strategy, we have explored the effects of interactions between growth factors (transforming growth factor β1 (Tgfb1) and colony stimulating factor 3 (Csf3), and culture environments (2D monolayer and 3D nanofiber scaffold) on chondrogenic differentiation. For this, we have examined cell morphologies, proliferation rates, viability, and gene expression profiles, and characterized the cartilaginous matrix formed in the chondrogenic cultures under different treatment regimens. Our data show that 3D cultures support higher proliferation rate than the 2D cultures. Tgfb1 promotes cell proliferation and viability in both types of culture, whereas Csf3 shows positive effects only in 3D cultures. Interestingly, our results indicate that the combined treatments of Tgfb1 and Csf3 do not affect cell proliferation and viability. The expression of cartilaginous matrix in different treatment groups indicates the presence of chondrocytes. We found that, at the end of differentiation stage 1, pluripotent markers were downregulated, while the mesodermal marker was upregulated. However, the expression of chondrogenic markers (col2a1 and aggrecan) was upregulated only in the 3D cultures. Here, we report an efficient, scalable, and convenient protocol for chondrogenic differentiation of iPS cells, and our data suggest that a 3D culture environment, combined with tgfb1 and csf3 treatment, promotes the chondrogenic differentiation.     

Preparation of porous SiC ceramics skeleton with low-cost and controllable gradient based on liquid crystal display 3D printing

In recent years, the demand for gradient porous ceramics is increasing in engineering field. By traditional process, the disadvantage of prepared gradient porous ceramics is its low porosity and uncontrollable pore gradient, which limits the wide application of gradient porous ceramics. In this study, the gradient porous ceramic skeleton (GPCS) was prepared by combining liquid crystal display (LCD) 3D printer with liquid silicon infiltration (LSI). Experimental results showed that the mass of ceramic powder in the ceramic slurry with optimal printing performance accounts for 45% of the mass of photosensitive resin, and the thermal decomposition rate of photosensitive resin is faster in the range of 300–450 °C. Furthermore, the effect of LSI temperature on the composition, microstructure and mechanical properties of GPCS was investigated. The GPCS is expected to be applied in the fields of energy storage, heat transfer and biofouling, among others.     

肠道病毒71型2A、3C、3D蛋白的研究进展

肠道病毒71型(Enterovirus type 71,EV71)感染是引起神经系统紊乱、肺水肿、肺出血等严重疾病的主要原因。非结构蛋白2A、3C、3D是EV71在宿主细胞内完成复制和存活的基础,具有不同于肠道病毒其他成员的结构和作用机制。2A和3C蛋白可抑制宿主细胞蛋白的表达,从而促进细胞凋亡,3C蛋白还可抑制天然免疫,3D蛋白与病毒的耐高温和高度变异适应性有关。一些小分子物质可在病毒入侵的不同阶段抑制EV71感染。本文就2A、3C、3D蛋白在EV71复制过程中的结构与功能特点以及一些小分子物质在病毒复制中的抑制作用作一综述。     

DED3F／KH-602共聚物（AFMS）的制备及其应用性能研究

在碱性催化剂的作用下,用1,3,5-三（甲基三氟丙基）环三硅氧烷（D3F）、八甲基环四硅氧烷（D4）和N,N-二甲基-β-氨乙基-T-氨丙基二甲氧基硅烷（KH-602）等单体共聚合,合成了一种织物后整理剂（AFMS）,并用红外光谱对其结构进行了表征。用10％（占AFMS的质量分数）的脂肪醇聚氧乙烯醚将其乳化,整理全棉织物。应用结果表明,AFMS的应用性能与n（D3F）：m（D4）及氨值等有关,在,n（D3F）：m（D4）为1：1时,随着氨值增大,整理织物的柔软性能、疏水性能提高。当氨值为0．5989mmol／g。水的接触角达到134．49°。     

浸润剂的制备及对3D打印产品力学性能的影响

以环氧树脂和丙烯酸酯类单体为主要原料制备了两种用于3D打印产品的浸润剂。用两种浸润剂和石蜡对3D打印的聚甲基丙烯酸甲酯(PMMA)试样进行了处理,研究了浸润剂对PMMA力学性能的影响。结果表明,反应型浸润剂对选择性激光烧结和喷墨砂型打印的产品有明显的增强作用,环氧浸润剂处理的产品经后处理后力学性能优于丙烯酸浸润剂处理的产品,黏度对环氧浸润剂的增强效果有较大影响。     

Effect of print path process on sintering behavior and thermal shock resistance of Al2O3 ceramics fabricated by 3D inkjet-printing

In this study, Al₂O₃ ceramics parts were printed by inkjet printing technology with different printed paths distributions, such as the spiral printed path, round trip straight printed path and ladder lap printed path. The influences of inkjet printed paths on sintering performance and thermal shock resistance of the Al₂O₃ green bodies were investigated. The sintering performance of the green sample with the ladder lap printed path is the highest among the three samples. Sintered at 1550?℃, its bulk density and porosity reached 3.73?g/cm³ and 10.80%, respectively. In addition, the thermal shock resistance of the sample with the step print path reached 11 times. The results suggest that the optimization of the printed path provides an effective way to print 3D ceramics with good performances through 3D inkjet-printing technology.     

湿度变化对交替3D打印试件微结构及力学性能的影响研究

本文提出一种全新的硅酸盐水泥(PC)与碱激发矿渣(AAS)交替3D打印工艺,并基于该工艺打印了硅酸盐水泥-碱激发矿渣复合试件。在试件干燥前后,分别采用X射线断层扫描成像技术(CT)分析了各复合试件以及碱激发矿渣打印试件的微观结构,并测试了各试件干燥前后的抗折与抗压强度。结果表明,碱激发矿渣与硅酸盐水泥的抗干缩性能不同,在内部湿度下降时,两种材料的打印界面容易因干缩不一致而开裂,引起打印成品微结构劣化以及力学性能下降。尽管如此,采用交替3D打印工艺,硅酸盐水泥有效弥补了碱激发矿渣强度的不足,打印成品的抗折与抗压强度均高于碱激发矿渣打印试件。对比逐层交替与逐列交替两种3D打印方法,逐层打印试件的抗折强度更高,而逐列打印试件的抗压强度更高。上述研究成果对3D打印混凝土技术的推广运用有一定指导意义。     

Effect of the nanoparticles on the morphology and mechanical performance of thermally blown 3D printed HIPS foams

Cellular polymer nanocomposites can combine high mechanical performance with low density. However, the manufacturing of porous nanocomposites into complex shapes can represent a challenge. Therefore, this article deals with the preparation, characterization, and 3D printing of porous nanocomposites. The filaments were extruded from the polymer nanocomposite filled by thermal chemical blowing agent, and then processed by 3D printing into the required shapes. In-situ and post-treatment foaming strategies were investigated and compared. The nanoparticles (NPs) significantly affected the processing, structure, thermal and mechanical properties of polymeric foams. The NPs, serving as a nucleating agent, allowed preparation of smaller pores and led to finer and more homogeneous foams. At the same time, they reinforced foam walls and thus improved mechanical properties. Moreover, NPs catalyzed decomposition of the blowing agent grains at lower temperature which brought about faster and more efficient foaming. This study showed the straightforward approach to prepare mechanically robust lightweight 3D printed materials.     

Effect of particle grading on the properties of photosensitive slurry and BaTiO3 piezoelectric ceramic via digital light processing 3D printing

To improve the density and piezoelectric constant of BaTiO₃ ceramics prepared by Digital Light Processing 3D printing, the properties of photosensitive slurry were investigated from the perspective of particle grading, and the nitrogen-air two-step debinding and sintering process on the relative density and electrical properties were explored. It was found that as the mass ratio of coarse particles increased, the viscosity, shear stress and cure depth of the slurry decreased. When the mass ratio of fine and coarse particles was 2:8 and sintered at 1350 °C, the ceramic had better performance, with relative density reaching 95.39 ± 0.63 %. The piezoelectric constant d₃₃ was 215 ± 13 pC/N, 29.52 % higher than the single-peak powder. The relative permittivity (ε_r) and polarization (P_r) were 978 and 16.656 μC/cm². Finally, BaTiO₃ ceramics with Triply Periodic Minimal Surface structures were prepared as piezoelectric sensors, which had the highest output voltage at the same displacement when the mass ratio was 2:8.     

氧化铁红颜料对白水泥基3D打印材料流变及可打印性能的影响

目前3D打印技术在建筑材料领域的研究主要集中在大型结构的建立和力学性能上,而对异形装饰及景观构件的研究还很少.本文采用白色硅酸盐水泥作为胶凝材料,并引入亚微米级粒度氧化铁红颜料来制备彩色水泥基3D打印材料,并研究氧化铁红颜料对白水泥基3D打印材料流变性能、可打印性能及力学性能的影响.结果表明,低掺量的颜料可以降低白水泥...