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.     

Photothermal effect of 3D printed hydroxyapatite composite scaffolds incorporated with graphene nanoplatelets

Porous scaffolds with photothermal effect could be used in the treatment of malignant bone tumors. Herein, graphene nanoplatelets were incorporated into the apatite/gelatin composites to construct porous scaffolds by 3D printing. Under near infrared laser irradiation, the composite scaffolds demonstrated high photothermal conversion efficiency. The temperature of scaffolds could be heated to 43 °C by controlling time and power of the laser irradiation, and then cooled to room temperature subsequently. Mild photothermal treatment (40–43 °C) was applied on MC3T3-E1 cells cultured on the scaffolds. It was found that after 3 cycles of treatment, the proliferation of MC3T3-E1 cells was significantly accelerated. It was suggested that the incorporation of graphene nanoplatelets into 3D printed hydroxyapatite composite scaffolds have the potential to accelerate bone regeneration after photothermal treatment for malignant bone tumors.     

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 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.     

3D printing of polycaprolactone/bioactive glass composite scaffolds for in situ bone repair

3D printing technology can fabricate customized scaffolds based on patient-derived medical images, so it has attracted much attention in the field of developing bone repair scaffolds. Polycaprolactone (PCL) is a suitable polymer for preparing bone repair scaffolds because of its good biocompatibility, thermal stability, excellent mechanical properties and degradable properties. However, PCL is a bioinert material and cannot induce new bone formation at the defect site. In this study, the bioactive material 58s bioactive glass was mixed into PCL to form PCL/bioactive glass composite material. The results of contact angle showed that the hydrophilicity of the scaffold was significantly enhanced with the increase of bioactive glass content. In vitro experiment results showed that, with the increase of bioactive glass content, cell adhesion and proliferation were enhanced, the expression levels of Runx2 and Collagen I(COL-I) were upregulated. The experimental results of in vivo radial defect repair in rats also showed that the effect of bone repair was improved with the increase of bioactive glass content. In conclusion, PCL customized bone repair scaffold containing 20% bioactive glass has widely potential used in the field of clinical bone repair.     

3D printing of NiZn ferrite architectures with high magnetic performance for efficient magnetic separation

Magnetic materials with desired architectures and high performance have become increasingly important for applications. In this work, NiZn ferrites with mesh structures have been successfully fabricated from preliminary precursors by three-dimensional (3D) printing accompanied by the solid-state reaction. The influence of compositions on structural and magnetic properties of NiZn ferrites were systematically investigated. It was obvious that the saturation magnetization was significantly enhanced to 77 emu/g for NiZn ferrites with a zinc concentration of 0.4, which was a much higher value compared to Ni ferrites. This is attributed not only to the well-known cationic distribution, but also to the grain growth with extraordinarily high crystallinity. Consequently, NiZn ferrites with intricate mesh structures were utilized for magnetic separation, and the distributions of magnetic flux density were simulated. Overall, the fabrication of NiZn ferrites by 3D printing is attractive for scaled-up applications, and also paves the promising avenue for magnetic separation.     

Doping polyvinyl alcohol can improve the injectability of biological ceramics in 3D printing and influence the adhesion of cells to the scaffolds after sintering

β tricalcium phosphate (β-TCP) is a common biological ceramic in bone tissue engineering due to its excellent biocompatibility and biodegradability. However, owing to its inherent properties of poor injectability and forming ability, the application of TCP in extrusion 3D printing is quite limited. To solve this problem, we innovatively printed gelatin and PVA (Polyvinyl alcohol) binary systems by taking advantage of the ability of gelatin to solidify rapidly at low temperatures and the ability of PVA to effectively improve phase separation during extrusion. Here, we fabricated a series of novel Gel-PVA-TCP scaffolds by incorporating different concentrations of PVA (5%, 10%, 15%) through 3D printing. Collectively, the addition of PVA made differences in three ways. First, compared to the PVA-free system, the novel printing system significantly improved the printability of TCP paste. The printing temperature was decreased to 35–45 °C by doping different concentrations of PVA. Next, the novel printing system maintained the excellent forming ability and printing precision of the scaffolds. Compared to the macropores of scaffolds without doping PVA (456.1 ± 11.2 μm), the macropores of Gel-PVA-TCP were 486.1 ± 26.5, 446.1 ± 15.2, and 443.7 ± 26.3 μm. Last, after sintering, the scaffolds with different concentrations of PVA exhibited similar compressive strength (3.82 ± 0.22, 3.34 ± 0.23, 3.74 ± 0.38, 3.47 ± 0.48 Mpa) and distinct micropores (4.44 ± 0.7, 1.54 ± 0.3, 2.59 ± 0.6, 3.59 ± 1.0 μm) on the surfaces of the scaffolds. Moreover, it was found that differences in the microstructure significantly facilitate the adhesion of bone marrow mesenchymal stem cells to scaffolds. Hence, the methods we provided hold a great promise for application in 3D printing techniques.     

A biopolymer‐based 3D printable hydrogel for toxic metal adsorption from water

Herein, we describe a 3D printable hydrogel that is capable of removing toxic metal pollutants from aqueous solution. To achieve this, shear‐thinning hydrogels were prepared by blending chitosan with diacrylated Pluronic F‐127 which allows for UV curing after printing. Several hydrogel compositions were tested for their ability to absorb common metal pollutants such as lead, copper, cadmium and mercury, as well as for their printability. These hydrogels displayed excellent metal adsorption with some examples capable of up to 95% metal removal within 30 min. We show that 3D printed hydrogel structures that would be difficult to fabricate by conventional manufacturing methods can adsorb metal ions significantly faster than solid objects, owing to their higher accessible surface areas. © 2019 Society of Chemical Industry     

Modification of hydroxyapatite (HA) powder by carboxymethyl chitosan (CMCS) for 3D printing bioceramic bone scaffolds

The poor mechanical properties of 3D printed HA bone scaffold is always a challenge in tissue engineering, to address this issue, carboxymethyl chitosan (CMCS) was proposed to modify HA bone scaffolds by a physical blending method in this research. A series of HA and HA/CMCS composite ceramic scaffolds were printed by using piezoelectric inkjet 3D printing technology, and their properties were investigated in terms of forming quality, structural morphology, mechanical properties, degradability, cytotoxicity, and cell adhesion growth. The results of forming quality and structural morphology show that with the increase of CMCS content, the forming quality of the samples deteriorated, the pore size and porosity increased. However, when the content of CMCS reached 5 wt%, obvious cracks appeared on the surface of the sample, and the forming quality was relatively poor. The mechanical testing results indicated the toughness of composites could be enhanced by incorporating CMCS into HA, which was attributed to the higher strength connections of the CMCS polymer network between HA particles and the stronger interaction between HA and CMCS molecules. FTIR spectra further revealed the strong hydrogen bonding interaction between CMCS and HA. Moreover, the degradation rate and mineralization ability of the sample increased with the content of CMCS, but the compressive strength during degradation increased with the CMCS content, indicating that incorporating CMCS into HA cannot only improve the mechanical property and biological activity of the scaffold but also makes up the defect of slow degradation of pure HA scaffold. Finally, the cytotoxicity, cell adhesion, and cell proliferation tests show that HA and HA/CMCS composite samples had good cytocompatibility, HA/CMCS sample with 3 wt% CMCS possessed the best bioactivity. In summary, HA/CMCS composite powder with 3 wt% CMCS content is the optimal matrix material for 3D printing bone scaffolds.     

3D打印制备三维石墨烯及其在水处理中的应用

石墨烯作为一类新型纳米材料,具有对水中各类污染物良好的吸附去除性能,但石墨烯纳米粉末态的性状使其在使用后难以从溶液中分离出来而造成二次污染。因此构建大体积的三维石墨烯结构,可以有效弥补水处理中纳米材料难以分离的问题。本文介绍了如今常用的三维结构制备方法,如模板法、自组装法等,但这些方法通常步骤烦琐、影响因素及所需条件较多等,在过程中易产生结构缺陷,从而影响制得的三维结构的力学性能。文中指出,3D打印法通过计算机数据调控,具有操作简便、结构设计精准、批量制备的优点,可制备出优良的三维结构体,并可通过对浆料组分的灵活调控进行改性或增加其力学性能。综上所述,配置满足3D打印黏度要求的浆料,并使制得的三维结构具备一定要求的力学性能,充分利用其精密的规模化生产,是使3D打印三维石墨烯适用于水处理的关键所在。     

3D gel printing of alumina ceramics followed by efficient multi-step liquid desiccant drying

Dense alumina ceramics were additively manufactured efficiently through a 3D gel printing process. Hydroxyethyl cellulose (HEC) was applied to ensure the printability and rigid of the gel made from boehmite. A multi-step liquid desiccant drying method was implemented to improve the drying efficiency. The results showed that the solid loading and HEC addition were two useful parameters for adjusting the rheology properties of the gel to make it suitable for 3D printing. With polyethylene glycol(PEG) added as liquid desiccants, the printed bodies with section size of 10 mm could be dried within 26 h during which the deformation and crack formation was avoided despite a high linear shrinkage of 45 % was encountered. The successful preparation of dense monolithic alumna ceramics parts with an average grain size of 1 μm, 99 % of the theoretical density and a flexural strength of 380 ± 45 MPa indicated the potential of this process.     

Fabrication of bone tissue engineering scaffolds with a hierarchical structure using combination of 3D printing/gas foaming techniques

The goal of this research was to study and optimize the structure and geometric features of scaffolds made using a combined method of 3D printing and gas foaming. This endeavor aimed to produce scaffolds with a hierarchical structure that closely resemble bone tissue. The study examined the effects of saturation pressure, foam temperature, and foam time on the scaffolds using response surface methodology (RSM). RSM is statistical technique used for optimizing and analyzing processes by modeling relationship between input variables and output responses. The results of multi-objective optimization showed that highest pressure (55 MPa), the shortest time (40 s), and the temperature of 68°C were the optimal conditions. RSM was also used to develop mathematical models of structural properties, dimensional accuracy, and mechanical strength, focusing on different foam parameters, which could be used to predict desired properties. Subsequently, the designed scaffold underwent MTT assay testing to assess cell toxicity indicating its biocompatibility. The results demonstrate that by using the correct foam parameters in combination with 3D printing, it is possible to achieve polymer scaffolds with proportional dimensions, geometry, and mechanical strength suitable for cell growth to use inside the human body.     

三维打印珍珠粉-硫酸钙/聚己内酯复合支架及性能研究

具有生物相容性的支架可以作为可控的细胞外环境,供细胞附着、增殖、分化以及组织生成,在组织工程中有着重要的作用。本研究运用三维打印技术制备了珍珠粉-硫酸钙/聚己内酯(Pearl-CaSO_4/PCL)复合支架,详细研究了珍珠粉含量对复合支架的理化性能和生物学性能的影响。结果表明,复合支架具有350mm左右的三维连通大孔,其孔隙率约60%,支架强度可达8 MPa。珍珠粉的复合能够有效调节复合支架的降解速率并稳定支架周围的体液环境。细胞实验结果表明,Pearl-CaSO_4/PCL复合支架能够促进骨髓间充质干细胞的增殖与分化,且与珍珠粉的含量呈正相关。因此,Pearl-CaSO_4/PCL复合支架在骨缺损修复领域具有应用前景。     

3D打印技术用于不规则骨缺损的重建与修复

为研究3D打印技术对不规则形状骨缺损模型的重建程度,和3D打印的可降解生物材料对脊椎骨缺损在12周内的修复的效果,本文随机选取一名病人,用其电子计算机断层扫描（computed tomography, CT）数据构建出不规则的三维脊柱缺损模型,选用聚己内酯（polycaprolactone, PCL）作为支架材料,运用3D打印技术打印出高度符合该病人骨缺损部位的人工骨支架。同时建立一个简单的兔子脊椎缺损模型,运用3D打印技术打印缺损尺寸的支架移植兔子体内,术后观察3个月,将兔子处死取出缺损部位,制作切片进行苏木素和伊红（Hematoxylin and Eosin, H&E）染色,染色结果表明缺损部位修复良好。     

3D打印超拉伸凝胶电解质及其在柔性铝空气电池中的应用

采用细菌纤维素（BC）、聚乙烯醇（PVA）为原料，通过3D打印与冻融循环法制备超拉伸凝胶电解质。采用SEM、接触角测量、XRD、EIS和拉伸测试对凝胶电解质物理特性、电化学性能及拉伸性能进行表征。实验结果表明，当m(BC)∶m(PVA)=0.6∶1时，基于3D打印制备的凝胶电解质具有稳定的三维网络结构、优异的拉伸性能和电化学性能，拉伸强度可达0.9 MPa、断裂伸长率可达961%、离子电导率为1.10×10-1 S/cm。将该凝胶电解质应用于柔性铝空气电池，功率密度可达21 mW/cm2，电流密度为20 mA/cm2时，铝阳极比容量为1124 mA?h/g，电池可稳定放电90 min。     

3D printing of high-purity silicon carbide

A method for advanced manufacturing of silicon carbide offering complete freedom in geometric complexity in the three-dimensional space is described. The method combines binder jet printing and chemical vapor infiltration in a process capable of yielding a high-purity, fully crystalline ceramic—attributes essential for ideal performance in very high-temperature applications or in the presence of displacement damage. Thermal conductivity and characteristic equibiaxial flexural strength of the resulting monolithic SiC at room temperature are 37 W·(m·K)⁻¹ and 297 MPa, respectively.     

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).     

3D printing of porous low-temperature in-situ mullite ceramic using waste rice husk ash-derived silica

The in-situ mullite (3Al₂O₃·2SiO₂) foams are fabricated by 3D printing (direct ink writing (DIW)) technique and utilize waste rice husk ash (RHA). The Al₂O₃-SiO₂ inks are prepared using an aqueous binder with α-alumina and two different silica sources, i.e., RHA extracted biogenic nano-silica (NS) and commercial silica (CS). The ink rheological features are first designed in terms of solid-to-liquid ratio and dispersant, and found that a higher amount of dispersant is needed for functionalization of NS-containing ink than CS (micro-sized) consisting of ink. Secondly, the DIW log-pile structures are fired at different temperatures (1200?1500 °C), and NS containing samples exhibited remarkable enhanced properties at a lower firing temperature than CS. At 1400 °C, alumina and RHA nano-silica entirely transformed into mullite and retained ～75 % porosity, ～8 MPa cold compressive strength, and thermal conductivity ～0.173 W/m·k that designate a simple and effective way to fabricate of mullite foamy structure.     

Evaluation of mechanical behavior,bioactivity, and cytotoxicity of chitosan/akermanite-TiO2 3D-printed scaffolds for bone tissue applications

This report aimed to evaluate the mechanical behavior, bioactivity, and cytotoxicity of novel chitosan/akermanite-TiO₂ (CS/AK/Ti) composite scaffolds fabricated using the 3D-printing method. The morphological and structural properties of these scaffolds were characterized by Fourier transform spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical behavior was examined by measuring the compressive strength, while the bioactivity was estimated in the simulated body fluid (SBF), and also the cytotoxicity of the scaffolds was assessed by conducting cell culturing experiments in vitro. It was found that the mechanical properties were considerably affected by the amount of TiO_2. The scaffolds had the possessed bone-like apatite forming ability, which indicated high bioactivity. Furthermore, L929 cells spread well on the surface, proliferated, and had good viability regarding the cell behaviors. The outcomes confirmed that the morphological, biological, and mechanical properties of developed 3D-composite scaffolds nearly mimicked the features of natural bone tissue. In summary, these findings showed that the 3D-printed scaffolds with an interconnected pore structure and improved mechanical properties were a potential candidate for bone tissue applications.