Glutaraldehyde crosslinked gelatin/hydroxyapatite nanocomposite scaffold,engineered via compound techniques

In this study, a scaffold was designed to be used in bone tissue repair and the effect of glutaraldehyde (GA) concentration as crosslinking agent was investigated. To mimic the mineral and organic component of natural bone, hydroxyapatite (HAp) and gelatin (GEL) were used as the main components of this composite. Nanopowders of HAp were synthesized and also used together with GEL to engineer a three‐dimensional nanocomposite scaffold. The results show that GEL/HAp nanocomposite is porous with three‐dimensional interconnected structure, pore sizes ranging from 300 to 500 μm, and about 85% porosity. In addition, increasing GA concentration provokes the enhancement of compressive strength until 1 w/v% GA solution followed by a reduction to 2.5%, whereas it causes work fracture to decrease. It was concluded that optimum concentration for crosslinking GEL matrix for this purpose is 1 w/v% GA solution. A specific combination of commonly used techniques applied to engineer a scaffold with almost ideal properties intended for the bone tissue engineering is introduced. In addition, scaffolds that are prepared via this compound process has the potential to be used in the solid free form applications and so being formed in any dimension and geometry relevant to the defect size and shape. POLYM. COMPOS., 31:2112–2120, 2010. © 2010 Society of Plastics Engineers     

Preparation and mechanical performance of SiCw/geopolymer composites through direct ink writing

Traditional geopolymer structures benefit from the durability, irradiation resistance, and environmental friendliness, but their brittleness limits their applications where repeated, impactive strains are imparted. This situation may be alleviated if complex structures with tunable geometry can be fabricated, for example, through 3D printing based on direct ink writing (DIW). In this research, SiC whisker/geopolymer (SiC_w/GP) composites were fabricated by the DIW for the first time. The rheological behaviors of the SiC_w/GP inks and the fracture behaviors of the printed samples were explored. The modified printing inks exhibited non-Newtonian fluid behavior (shear-thinning). Subsequently, a series of lightweight architected structures were fabricated, and they revealed how reinforcement and architecture of the printed structures could influence both the strength and toughness of the SiC_w/GP composites.     

Extrusion-based 3D printing alumina-silica inks: Adjusting rheology and sinterability incorporating waste derived nanoparticles

The nanoparticle (NP) exhibits numerous distinctive and extraordinary properties than micron level and up. The inclusion of NP effects in the rheological and densification behavior of extrusion-based (direct ink writing (DIW)) inks has been extensively investigated. The aqueous-based alumina-silica inks were first designed using waste rice husk ash (RHA) derived nano-silica (NS) (0–10 wt%) and found that the solid-to-liquid ratio reduces continuously with NS addition for printable rheology. For functionalization of NS, dispersant requirement is increased that improve the solids loading of inks. Second, the optimized inks are printed via DIW technique and sintered at a temperature of 1400–1650 °C. The NS has remarkably enhanced the shrinkage, density, and morphology of sintered DIW specimens and 7.5 wt% RHA NS reduces the sintering temperature ∼150 °C. Incorporating NP in the 3D printing ink is a clean approach to filling pores generated by binder-burnout and fabricating a dense ceramic at a low temperature.     

UV-assisted direct ink writing of Si3N4/SiC preceramic polymer suspensions

Direct ink writing (DIW) offers a flexible and readily available processing route for achieving ceramic components with complex shapes and geometries. The successful printing of ceramic green bodies using DIW typically requires the formulation of particle-loaded inks having a narrow window of rheological properties that enable both flow through the nozzle and support the weight of additional layers. Herein, we present a method for DIW that employs UV-curing to enable printing of otherwise unprintable inks. The inks used in this study are suspensions consisting of a commercially available polycarbosilane precursor and silicon nitride, Si₃N₄, powders. A diacrylate cross-linker and photointiator were employed to enable UV-curing. The effect of cross-linker content on UV-rheology and cure depth as they pertain to printing, and slump in self-supported lattice structures, are discussed. UV-assisted DIW produced components of a high degree of complexity, capable of supporting over-hanging structures, low shrinkage, and relatively high degree of ceramic conversion     

Effect of ZnO reinforcement on the compressive properties,in vitro bioactivity,biodegradability and cytocompatibility of bone scaffold developed from bovine bone-derived HAp and PMMA

In this study, the effect of zinc oxide (ZnO) incorporation on the properties of Hydroxyapatite (HAp)/Poly(methyl methacrylate) (PMMA)/ZnO based composite bone scaffold is investigated. HAp is derived from calcination of bovine bone bio-waste and ZnO is synthesized by direct precipitation technique. Porous scaffolds are developed by gas foaming process using ammonium bicarbonate as the foaming agent and adding ZnO nanoparticles (NPs) at 2.5, 5, 7.5 and 10% (w/w) respectively. Incorporation of ZnO up to 5% (w/w) is found to significantly enhance the porosity, compressive strength, thermal stability and swelling properties of the developed scaffolds. In-vitro bioactivity and biodegradability assessment using simulated body fluid (SBF) show improved results of 5% ZnO loaded scaffolds. Furthermore, the composite scaffold show enhanced cytocompatibility during the in vitro cytotoxicity test performed using XTT assay. A comprehensive study on the scaffold properties shows that 5% ZnO composite scaffold exhibits the best-optimized properties suitable for bone tissue engineering applications.     

Development of bone scaffold using Puntius conchonius fish scale derived hydroxyapatite: Physico-mechanical and bioactivity evaluations

Naturally derived Hydroxyapatite (HAp) from fish scale is finding wide applications in the development of bone scaffold to promote bone regeneration. But porous HAp scaffold is fragile in nature making it unsuitable for bone repair or replacement applications. Thus, it is essential to improve the mechanical property of HAp scaffolds while retaining the interconnected porous structure for tissue ingrowth in vivo. In this study solvent casting particulate leaching technique is used to develop novel Puntius conchonius fish scale derived HAp bone scaffold by varying the wt.% of the HAp from 60 to 80% in PMMA matrix. Physico-chemical, mechanical, structural and bioactive properties of the developed scaffolds are investigated. The obtained results indicate that HAp-PMMA scaffold at 70?wt % HAp loading shows optimal properties with 7.26?±?0.45?MPa compressive strength, 75?±?0.8% porosity, 8.0?±?0.68% degradation and 190?±?11% water absorption. The obtained results of the scaffold can meet the physiological demands to guide bone regeneration. Moreover, in vitro bioactivity analysis also confirms the formation of bone like apatite in the scaffold surface after 28 days of SBF immersion. Thus, the developed scaffold has the potential to be effectively used in bone tissue engineering applications.     

Study of microstructural,mechanical, and biomedical properties of zirconia/hydroxyapatite ceramic composites

In this study, hydroxyapatite was obtained by the sol-gel method, and zirconia/hydroxyapatite composites (YSZ/HAp) were produced with weight proportions of 95/5, 90/10, 85/15, and 80/20, respectively. The samples were characterized by X-ray diffraction (XRD), Archimedes' principle, Fourier-transform infrared spectroscopy (FT-IR), Vickers microhardness, scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). The calvarial critical-sized defect experimental model in rats was used to evaluate the biological interaction between YSZ/HAp scaffolds and bone tissue by Micro CT analysis. The XRD patterns of composites showed the major intensity of the zirconia phase and lower intensity of the hydroxyapatite phase, but the FT-IR analysis confirmed the presence of hydroxyapatite. Dense composite materials were verified by way of the Archimedes’ principle, where the YSZ/HAp 85/15 sample had lower apparent porosity (0.60%) and water absorption (0.10%). Vickers microhardness showed that composite material hardness decreased with the increase of hydroxyapatite, varying from 1367.43 to 711.37 HV. SEM images were possible to quantify the crack sizes in the indentations and to identify the elements presents by EDS, while FESEM was applied to analyze the morphology of the powders and microstructure of the composites. Among the composite studied, YSZ/HAp 85/15 and YSZ/HAp 80/20 samples were the compositions that demonstrated the best mechanical behavior with a fracture toughness of 9.2 and 9.3 MPa m^1/2, respectively. The YSZ/HAp scaffold showed an interaction with bone tissue. The percent bone volume (BV/TV, p < 0.001) and bone mineral density (BMD, p < 0.01) were significantly increased in Zirconia/hydroxyapatite scaffold.     

Fabrication of Hydroxyapatite with Bioglass Nanocomposite for Human Wharton’s-Jelly-Derived Mesenchymal Stem Cell Growing Substrate

Recently, composite scaffolding has found many applications in hard tissue engineering due to a number of desirable features. In this present study, hydroxyapatite/bioglass (HAp/BG) nanocomposite scaffolds were prepared in different ratios using a hydrothermal approach. The aim of this research was to evaluate the adhesion, growth, viability, and osteoblast differentiation behavior of human Wharton’s-jelly-derived mesenchymal stem cells (hWJMSCs) on HAp/BG in vitro as a scaffold for application in bone tissue engineering. Particle size and morphology were investigated by TEM and bioactivity was assessed and proven using SEM analysis with hWJMSCs in contact with the HAp/BG nanocomposite. Viability was evaluated using PrestoBlue^TM assay and early osteoblast differentiation and mineralization behaviors were investigated by ALP activity and EDX analysis simultaneously. TEM results showed that the prepared HAp/BG nanocomposite had dimensions of less than 40 nm. The morphology of hWJMSCs showed a fibroblast-like shape, with a clear filopodia structure. The viability of hWJMSCs was highest for the HAp/BG nanocomposite with a 70:30 ratio of HAp to BG (HAp70/BG30). The in vitro biological results confirmed that HAp/BG composite was not cytotoxic. It was also observed that the biological performance of HAp70/BG30 was higher than HAp scaffold alone. In summary, HAp/BG scaffold combined with mesenchymal stem cells showed significant potential for bone repair applications in tissue engineering.     

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.     

Rheological behavior of multi-sized SiC inks containing polyelectrolyte complexes specifically for direct ink writing

In order to simultaneously improve both the solid loading and rheological behavior of ceramic ink during direct ink writing (DIW) process, the polyelectrolyte complexes have been used as rheological modifiers. Based on the Funk-Dinger function, the maximum solid loading of multi-sized SiC ink reached 63 vol%. The viscoelasticity of SiC inks with different [COOH]:[NH_x] molar ratios was investigated and the mechanism of polyionic chains on rheology was analyzed. When the [COOH]:[NH_x] molar ratio was 1:0.1, the SiC ink exhibited excellent thixotropic behavior and formability. The effect of particle size on rheological behavior of SiC ink was investigated to clarify the correlation between polyelectrolyte complexes and multi-sized SiC.     

Tetracycline hydrochloride-containing poly (ε-caprolactone)/poly lactic acid scaffold for bone tissue engineering application: in vitro and in vivo study

In the current study, tetracycline hydrochloride (TCH), an antibiotic against most of the medically relevant bacteria, was incorporated into poly (ε-caprolactone)/poly lactic acid solution in order to develop a composite scaffold with both antibacterial and osteoinductive properties for the repair of infected bone defects. The composite scaffolds were produced from poly (ε-caprolactone) (PCL) and poly lactic acid (PLA) solution (1:1 (w/w)) incorporated with 3, 5, and 10% (w/w) of TCH by thermally induced phase separation technique. The scaffolds were evaluated regarding their morphology, wettability, porosity, degradation, mechanical properties, and cellular response. The scaffold containing 10% of TCH (PCL/PLA/TCH10%) was chosen as the optimum scaffold for further investigation in a rat femoral defect model. The study showed that after eight weeks, the bone formation was relatively higher in PCL/PLA/TCH10%-treated group with completely filled defect when compared with control (PCL/PLA scaffold without TCH). Histopathological evaluation showed that the defect in PCL/PLA/TCH10%-treated group was fully replaced by new bone and connective tissue. Our results provide evidence supporting the possible applicability of TCH-containing scaffolds for successful bone regeneration.     

Synthesis of waterborne acrylic copolymer resin as a binding agent for the development of water-based inks in the printing application

In this study, a new waterborne acrylic copolymer resin (acrylic-co-resin) was synthesized to develop water-based printing inks on polyester (PET) film. The synthesized acrylic resin showed good water solubility, high acid value (120 mg KOH/g), about 57% solid content. The developed water-based inks (cyan, magenta, and yellow) exhibited small particle size (<1 μm) and optimum surface energy within required values (31.5, 32, and 30 mN/m) for good adhesion of ink upon PET films. The developed inks also showed good storage stability for 30 days. Further, to evaluate the application performance, the inks were printed on corona-treated PET films at room temperature, and the ink drying time was measured. Further, the inks were printed on the corona-treated PET film to evaluate the application performance. The developed inks showed a short drying time (7–9 s), which indicates their fast drying nature. Moreover, the developed inks showed good printability, color strength, high adhesion, and excellent rub-resistant properties. Thus, the overall results demonstrated the potential of water-based inks in printing applications.     

Surface‐engineered hydroxyapatite nanocrystal/ poly(ε‐caprolactone) hybrid scaffolds for bone tissue engineering

To achieve novel polymer/bioceramic composite scaffolds for use in materials for bone tissue engineering, we prepared organic/inorganic hybrid scaffolds composed of biodegradable poly(ε‐caprolactone) (PCL) and hydroxyapatite (HA), which has excellent biocompatibility with hard tissues and high osteoconductivity and bioactivity. To improve the interactions between the scaffolds and osteoblasts, we focused on surface‐engineered, porous HA/PCL scaffolds that had HA molecules on their surfaces and within them because of the biochemical affinity between the biotin and avidin molecules. The surface modification of HA nanocrystals was performed with two different methods. Using Fourier transform infrared, X‐ray diffraction, and thermogravimetric analysis measurements, we found that surface‐modified HA nanocrystals prepared with an ethylene glycol mediated coupling method showed a higher degree of coupling (%) than those prepared via a direct coupling method. HA/PCL hybrid scaffolds with a well‐controlled porous architecture were fabricated with a gas‐blowing/particle‐leaching process. All HA/PCL scaffold samples exhibited approximately 80–85% porosity. As the HA concentration within the HA/PCL scaffolds increased, the porosity of the HA/PCL scaffolds gradually decreased. The homogeneous immobilization of biotin‐conjugated HA nanocrystals on a three‐dimensional, porous scaffold was observed with confocal microscopy. According to an in vitro cytotoxicity study, all scaffold samples exhibited greater than 80% cell viability, regardless of the HA/PCL composition or preparation method. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of the AEO9/alcohol/alkane/water reverse microemulsion ceramic inks

Reverse microemulsion method was applied and the AEO₉/alcohol/alkane/water system was chosen to prepare ceramic inks for forming by jet-printing. The ceramic inks were prepared by reaction after mixing the zirconium oxychloride and ammonia reverse microemulsions homogeneously through vigorous stirring. The physicochemical properties of the ZrO₂ ceramic inks were systematically determined and discussed based on the requirements of the ink-jet printers available. They generally met the requirements for the drop on demand printers and were adjusted and improved by adding a small amount of alcohol and inorganic electrolyte to meet the demands for continuous ink-jet printers. It was shown that the ceramic ink with viscosity below 18 mPa s and conductivity close to 100 mS m⁻¹ was obtained after modification. Transmission electron microscope observation showed that ZrO₂ nanoparticles in the reverse microemulsion were very well dispersed and the stability of the inks was excellent. Besides, several ceramic ink compositions with bicontinuous structure were specially designed based on the phase diagram, and the changes of water-dissolving amount into the system was investigated aiming to increase the concentration of ZrO₂ ceramic ink.     

One‐Pot Fabrication of Poly(ε‐Caprolactone)‐Incorporated Bovine Serum Albumin/Calcium Alginate/Hydroxyapatite Nanocomposite Scaffolds by High Internal Phase Emulsion Templates

In this work, the authors report an effective one‐pot method to prepare poly(ε‐caprolactone) (PCL)‐incorporated bovine serum albumin (BSA)/calcium alginate/hydroxyapatite (HAp) nanocomposite (NC) scaffolds by templating oil‐in‐water high internal phase emulsion (HIPE), which includes alginate, BSA, and HAp in water phase and PCL in oil phase. The water phase of HIPEs is solidified to form hydrogels containing emulsion droplets via gelation of alginate induced by Ca²⁺ ions released from HAp. And the prepared hydrogels are freeze‐dried to obtain PCL‐incorporated porous scaffolds. The obtained scaffolds possess interconnected pore structures. Increasing PCL concentration clearly enhances the compressive property and BSA stability, decreases the swelling ratio of scaffolds, which assists in improving the scaffold stability. The anti‐inflammatory drug ibuprofen can be highly efficiently loaded into scaffolds and released in a sustained rate. Furthermore, mouse bone mesenchymal stem cells can successfully proliferate on the scaffolds, proving the biocompatibility of scaffolds. All results show that the PCL‐incorporated NC scaffolds possess promising potentials in tissue engineering application.

     

Development of Electrospun Composite Fibers in Multiscale Structure and Investigating the Performance on Proliferation and Osteogenic Differentiation of ADSCs

Electrospun composite membranes in multiscale structures are developed for bone tissue engineering. Aligned polycaprolactone (PCL) fibers entrapping CA‐HAp microparticles (containing CaCO₃, hydroxyapatite, and casein in a hierarchical organization) are electrospun to find whether synergistic effects of fiber alignment and CA‐HAp microparticles on improving osteogenic differentiation can be obtained. CA‐HAp microparticles are in a spherical morphology of 1.42 ± 0.26 µm. Their presence increases fiber diameter and does not significantly affect fiber alignment. On all membranes, adipose derived stem cells (ADSCs) from humans spread very well. On a random group, cells distribute randomly and the presence of CA‐HAp microparticles facilitates cell proliferation, especially for the one at CA‐HAp/PCL 50 wt%; the one at CA‐HAp/PCL 20 wt% shows significantly much higher alkaline phosphatase (ALP) activity (112.0% higher) than the pure PCL membrane. On aligned samples, cells align along fibers and expression of ALP is enhanced. However, at the same composition (CA‐HAp/PCL 20 wt%), the random sample has much higher ALP activity than the aligned sample. The expressions of osteogenic marker genes are also evaluated. Combining the results and the applicability of membranes together, the random membrane at CA‐HAp/PCL 20 wt% is the best candidate for bone tissue engineering.     

Direct ink writing of chopped carbon fibers reinforced polymer-derived SiC composites with low shrinkage and high strength

The chopped carbon fiber reinforced SiC (C_f/SiC) composite has been regarded as one of the excellent high-temperature structural materials for applications in aerospace and military fields. This paper presented a novel printing strategy using direct ink writing (DIW) of chopped fibers reinforced polymer-derived ceramics (PDCs) with polymer infiltration and pyrolysis (PIP) process for the fabrication of C_f/SiC composites with high strength and low shrinkage. Five types of PDCs printing inks with different C_f contents were prepared, their rheological properties and alignment of carbon fiber in the printing filament were studied. The 3D scaffold structures and bending test samples of C_f/SiC composites were fabricated with different C_f contents. The results found that the C_f/SiC composite with 30 wt% C_f content has high bending strength (～ 7.09 MPa) and negligible linear shrinkage (～ 0.48%). After the PIP process, the defects on the C_f/SiC composite structures were sufficiently filled, and the bending strength of C_f/SiC composite can reach up to about 100 MPa, which was about 30 times greater than that of the pure SiC matrix without C_f. This work demonstrated that the printed C_f/SiC composites by using this method is beneficial to the development of the precision and complex high-temperature structural members.     

Mechanical and dielectric properties of 3D printed highly porous ceramics fabricated via stable and durable gel ink

A novel, efficient, versatile strategy was carried out to fabricate highly porous ceramic parts based on the combination of strong colloidal gel ink fabricated with high boiling point organic solvents and DIW technique. The preparation and optimization of inks and the effect of heating temperature on the phase composition, microstructure, mechanical properties and dielectric properties of ceramic parts were systematically investigated. The strong colloidal ink exhibits excellent ambient stability and printability. The sintering temperatures bring about the evolution of phases, structural mechanical properties and dielectric properties of ceramic parts. Ultimately, Si₂N₂O single wall ceramic parts with a frame density of 1.07?1.14 g/cm³ and an apparent porosity of 53.13 ± 1.29% were successful fabricated. The dielectric constant and dielectric loss of Si₂N₂O sample (1650℃) are only 4.24 and 0.0049, respectively. This strategy provides a reference for in-situ synthesis of high-performance porous ceramic components based on the DIW.     

塑料水性凹印油墨附着性能的研究

采用合适的颜基比和分散剂制备了塑料水性凹印油墨基墨,用与基墨具有良好相容性的树脂溶液调稀基墨,添加各种助剂以改善油墨样品的印刷适性,探讨了颜基比、树脂溶液、助剂对油墨附着力的影响。结果表明:基墨中颜基比为3:1、分散剂为1.5%时油墨在PET和BOPP塑料表面均有较好的附着力,制备油墨时,使用50%的AZ-3808树脂溶液并添加1.5%异丙醇或1.5%润湿剂时,油墨在PET塑料表面具有较好的附着力,使用50%的1424树脂和1437树脂的混合溶液并添加1.5%异丙醇时,油墨在BOPP塑料表面具有较好的附着力。