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Powder-based inkjet 3D printing method is one of the most attractive solid free form techniques. It involves a sequential layering process through which 3D porous scaffolds can be directly produced from computer-generated models. 3D printed products' quality are controlled by the optimal build parameters. In this study, Calcium Sulfate based powders were used for porous scaffolds fabrication. The printed scaffolds of 0.8 mm pore size, with different layer thickness and printing orientation, were subjected to the depowdering step. The effects of four layer thicknesses and printing orientations, (parallel to X, Y and Z), on the physical and mechanical properties of printed scaffolds were investigated. It was observed that the compressive strength, toughness and Young's modulus of samples with 0.1125 and 0.125 mm layer thickness were more than others. Furthermore, the results of SEM and μCT analyses showed that samples with 0.1125 mm layer thickness printed in X direction have more dimensional accuracy and significantly close to CAD software based designs with predefined pore size, porosity and pore interconnectivity.

Controlled pore size and desirable internal architecture of bone scaffolds play a significant role in bone regeneration efficiency. In addition to choosing appropriate materials, the manufacturing method is another significant factor in fabricating the ideal scaffold. In this study, scaffolds were designed and fabricated by the fused filament fabrication (FFF) technique. Polycaprolactone (PCL) and composites films with various percentages of hydroxyapatite (HA) (up to 20%wt) were used to fabricate filaments. The influence of (HA) addition on the mechanical properties of filaments and scaffolds was investigated. in vitro biological evaluation was examined as well as the apatite formation in simulated body fluid (SBF). The addition of HA particles increased the compressive strength and Young’s modulus of filaments and consequently the scaffolds. Compared to PCL, Young’s modulus of PCL/HA20% filament and three-dimensional (3D) printed scaffold has increased by 30% and 50%, respectively. Also, Young’s modulus for all scaffolds was in the range of 30–70 MPa, which is appropriate to use in spongy bone. Besides, the MTT assay was utilized to evaluate cell viability on the scaffolds. All the samples had qualified cytocompatibility, and it would be anticipated that addition of HA particles raise the biocompatibility in vivo. Alkaline phosphatase (ALP) evaluation shows that the addition of HA caused higher ALP activity in the PCL/HA scaffolds than PCL. Furthermore, calcium deposition in the PCL/HA specimens is higher than control. In conclusion, the addition of HA particles into the PCL matrix, as well as utilizing an inexpensive commercial FFF device, lead to the fabrication of scaffolds with proper mechanical and biological properties for bone tissue engineering applications.

Recently, nanocomposites (NCs) based on Layered Double Hydroxides (LDH) and compression polymers have attracted a lot of bioengineer’s attentions. Because unlike non-composite materials, these compounds offer significant potential for superior behaviors. These materials exhibit good properties such as excellent bending, dimensional stability, cheap gas absorption, enhancement of thermal properties, ignition and mechanical delay. Such reinforcements occur in compression polymer matrices and adjustable properties of LDHs due to the intermediate effects of uniform and homogeneous dispersion of high dimensional LDH nanofillers. In the present study, polycaprolactone (PCL) polymer solutions containing different amounts of LDH (1%, 3% and 5%) were electrospun and the resulting fibers were structurally analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, using porosity, contact angle, degradation test, mechanical strength test, cell adhesion test and quantitative toxicity test (MTT), and cellular properties were investigated. During the studies, all scaffolds had a uniform surface and diameter with the same porosity. Also, with a 1 wt% and 3 wt% LDH, the tissue diameter decreased and increased with addition of 5 wt% LDH. In addition, increased of LDH leads to decreased in the contact angle of the structure. The degradation test result showed an increase in the rate of degradation with increasing LDH amount. The results of tensile and MTT tests showed an increase in tensile strength and cell proliferation with addition of LDH reinforcement. In cell adhesion test, the highest level of adhesion was reported in the sample with 1 wt% LDH. In general, it can be concluded that the sample containing 5 wt% LDH has optimal properties compared to other scaffolds and can be proper for tissue engineering.

Currently, material synthesis and processing developments allow the design of increasingly advanced scaffolds for bone tissue engineering. The purpose of this study is to fabricate hybrid scaffolds by embedding electrospun polycaprolactone (PCL) or layered double hydroxides (LDH)/PCL nanofiber mats into 3D printed circular PCL grids with 400 µm strands using a PCL solution as glue. Structural analysis revealed that LDH increased surface roughness in PCL mats in addition to reducing fiber diameter. FESEM images showed that the size of the 3D printed strands and pores was about the same as in the original design, and nanofiber mats were flawlessly placed between the 3D printed grids. The porosity of the scaffolds was determined through BET analysis. Young’s modulus of the scaffolds was determined using a compressive test conducted in dry and wet conditions. Hybrid scaffolds with LDH/PCL nanofiber mats showed significantly higher Young’s modulus than 3D printed grids and hybrid scaffolds with PCL nanofiber mats ( P  < 0.05). In vitro studies showed the positive effect of LDH on enhancing hybrid scaffolds’ bioactivity and biodegradation rate. The calcium/phosphate ratio in the hybrid scaffold containing LDH was closer to the stoichiometric calcium/phosphate ratio in natural bone. MG-63 cell lines were cultured to assess the scaffold’s biocompatibility. Cell adhesion, alkaline phosphatase activity, and calcium deposition were significantly enhanced in hybrid scaffolds with LDH/PCL nanofiber mats. Considering the results, this hybrid scaffold exhibits favorable bone tissue engineering characteristics. Graphical Abstract

The ability of inkjet-based 3D printing (3DP) to fabricate biocompatible ceramics has made it one of the most favorable techniques to generate bone tissue engineering (BTE) scaffolds. Calcium sulfates exhibit various beneficial characteristics, and they can be used as a promising biomaterial in BTE. However, low mechanical performance caused by the brittle character of ceramic materials is the main weakness of 3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the starting powder and binder solution causes products to have high toxicity levels. A post-processing treatment is usually employed to improve the physical, chemical, and biological behaviors of the printed scaffolds. In this study, the effects of heat treatment on the structural, mechanical, and physical characteristics of 3DP calcium sulfate prototypes were investigated. Different microscopy and spectroscopy methods were employed to characterize the printed prototypes. The in vitro cytotoxicity of the specimens was also evaluated before and after heat treatment. Results showed that the as-printed scaffolds and specimens heat treated at 300°C exhibited severe toxicity in vitro but had almost adequate strength. By contrast, the specimens heat treated in the 500°C-1000°C temperature range, although non-toxic, had insufficient mechanical strength, which was mainly attributed to the exit of the organic binder before 500°C and the absence of sufficient densification below 1000°C. The sintering process was accelerated at temperatures higher than 1000°C, resulting in higher compressive strength and less cytotoxicity. An anhydrous form of calcium sulfate was the only crystalline phase existing in the samples heated at 500°C-1150°C. The formation of calcium oxide caused by partial decomposition of calcium sulfate was observed in the specimens heat treated at temperatures higher than 1200°C. Although considerable improvements in cell viability of heat-treated scaffolds were observed in this study, the mechanical properties were not significantly improved, requiring further investigations. However, the findings of this study give a better insight into the complex nature of the problem in the fabrication of synthetic bone grafts and scaffolds via post-fabrication treatment of 3DP calcium sulfate prototypes.

In recent years, nanotechnology in merging with biotechnology has been employed in the area of cancer management to overcome the challenges of chemopreventive strategies in order to gain promising results. Since most biological processes occur in nano scale, nanoparticles can act as carriers of certain drugs or agents to deliver it to specific cells or targets. In this study, we intercalated Epigallocatechin-3-Gallate (EGCG), the most abundant polyphenol in green tea, into Ca/Al-NO3 Layered double hydroxide (LDH) nanoparticles, and evaluated its efficacy compared to EGCG alone on PC3 cell line. The EGCG loaded LDH nanohybrids were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM) and nanosizer analyses. The anticancer activity of the EGCG-loaded LDH was investigated in prostate cancer cell line (PC3) while the release behavior of EGCG from LDH was observed at pH 7.45 and 4.25. Besides enhancing of apoptotic activity of EGCG, the results showed that intercalation of EGCG into LDH can improve the anti- tumor activity of EGCG over 5-fold dose advantages in in-vitro system. Subsequently, the in-vitro release data showed that EGCG-loaded LDH had longer release duration compared to physical mixture, and the mechanism of diffusion through the particle was rate-limiting step. Acidic attack was responsible for faster release of EGCG molecules from LDH at pH of 4.25 compared to pH of 7.4. The results showed that Ca/Al-LDH nanoparticles could be considered as an effective inorganic host matrix for the delivery of EGCG to PC3 cells with controlled release properties.

Purpose This paper aims to investigate the mechanical behavior of three-dimensional (3D) calcium sulfate porous structures created by a powder-based 3D printer. The effects of the binder-jetting and powder-spreading orientations on the microstructure of the specimens are studied. A micromechanical finite element model is also examined to predict the properties of the porous structures under the load. Design/methodology/approach The authors printed cylindrical porous and solid samples based on a predefined designed model to study the mechanical behavior of the prototypes. They investigated the effect of three main build bed orientations (x, y and z) on the mechanical behavior of solid and porous specimens fabricated in each direction then evaluated the micromechanical finite-element model for each direction. The strut fractures were analyzed by scanning electron microscopy, micro-computed tomography and the von Mises stress distribution. Findings Results showed that the orientation of powder spreading and binder jetting substantially influenced the mechanical behavior of the 3D-printed prototypes. The samples that were fabricated parallel to the applied load had higher compressive strength compared with those printed perpendicular to the load. The results of the finite element analysis agreed with the results of the experimental mechanical testing. Research limitations/implications The mechanical behavior was studied for the material and the 3D-printing machine used in this research. If one were to use another material formulation or machine, the printing parameters would have to be set accordingly. Practical implications This work aimed to re-tune the control factors of an existing rapid prototyping process for the given machine. The authors achieved these goals without major changes in the already developed hardware and software architecture. Originality/value The results can be used as guidelines to set the printing parameters and a model to predict the mechanical properties of 3D-printed objects for the development of patient- and site-specific scaffolds.

Purpose This study aims to develop a simplified bioink preparation method that can be applied to most hydrogel bioinks used in extrusion-based techniques. Design/methodology/approach The parameters of the bioprinting process significantly affect the printability of the bioink and the viability of cells. In turn, the bioink formulation and its physicochemical properties may influence the appropriate range of printing parameters. In extrusion-based bioprinting, the rheology of the bioink affects the printing pressure, cell survival and structural integrity. Three concentrations of alginate-gelatin hydrogel were prepared and printed at three different flow rates and nozzle gauges to investigate the print parameters. Other characterizations were performed to evaluate the hydrogel structure, printability, gelation time, swelling and degradation rates of the bioink and cell viability. An experimental design was used to determine optimal parameters. The analyses included live/dead assays, rheological measurements, swelling and degradation. Findings The experimental design results showed that the hydrogel flow rate substantially influenced printing accuracy and pressure. The best hydrogel flow rate in this study was 10 ml/h with a nozzle gauge of 18% and 4% alginate. Three different concentrations of alginate-gelatin hydrogels were found to exhibit shear-thinning behavior during printing. After seven days, 46% of the structure in the 4% alginate-5% gelatin sample remained intact. After printing, the viability of skin fibroblast cells for the optimized sample was 91%. Originality/value This methodology offers a straightforward bioink preparation method applicable to the majority of hydrogels used in extrusion-based procedures. This can also be considered a prerequisite for cell printing.

A correct understanding of the process of scaffold degradation can help a proper scaffold design of bone regeneration. Polylactide acid (PLA) scaffolds are a suitable alternative for bone regenerations due to their mechanical and biodegradable properties, but their degradation tests are time-consuming and costly. Using reliable accelerated methods for in vitro experiments to save time and cost and give valid test results for scaffold degradation can be critical. In this study, two kinds of scaffolds with 60% and 80% porosities have been fabricated using the fused deposition modeling (FDM) technique. The accelerated degradation method was investigated using an alkaline solution of 0.074 M NaOH at 37 °C with pH 12.5, and the results were analyzed. The degradation of PLA scaffolds subjected to hydrolysis was evaluated based on changes in weight loss, molecular weight distribution, mechanical properties, crystallinity, and morphological analyses, for a 50 day time interval. It was found that changes in the scaffolds’ porosity greatly influence weight loss, molecular weight loss, and decrease in mechanical properties. A 20% increase in porosity leads to 2.6% more weight loss and 2% greater average molecular weight loss. Rapid yield stress reduction was observed in both porosities. Elastic modulus had a 91% reduction in 80% and a 42% reduction in 60% porosity scaffolds. The morphological changes are more evident in porosity of 80% with surface erosion in both scaffolds. The 60% porosity scaffolds showed better mechanical properties and integrity until the end of the test. Graphical abstract

In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD). Results show that the morphology of HA-Alumina-Zirconia coatings is more homogenous in the second process with 2 hours final sol stirring time, 20 hours aging time under stirring at 60, 675°C calcination temperature for coating and 850°C for powder and 60mm/min rate of dip coating.