Cell-laden scaffolds are widely investigated in tissue engineering because they can provide homogenous cell distribution after long culture periods, and deposit multiple types of cells into a ...designed region. However, producing a bioceramic 3D cell-laden scaffold is difficult because of the low processability of cell-loaded bioceramics. Therefore, designing a 3D bioceramic cell-laden scaffold is important for ceramic-based tissue regeneration. Here, we propose a new strategy to fabricate an alpha-tricalcium-phosphate (α-TCP)/collagen cell-laden scaffold, using preosteoblasts (MC3T3-E1), in which the volume fraction of the ceramic exceeded 70% and was fabricated using a two-step printing process. To fabricate a multi-layered cell-laden scaffold, we manipulated processing parameters, such as the diameter of the printing nozzle, pneumatic pressure, and volume fraction of α-TCP, to attain a stable processing region. A cell-laden pure collagen scaffold and an α-TCP/collagen scaffold loaded with cells via a simple dipping method were used as controls. Their pore geometry was similar to that of the experimental scaffold. Physical properties and bioactivities showed that the designed scaffold demonstrated significantly higher cellular activities, including metabolic activity and mineralization, compared with those of the controls. Our results indicate that the proposed cell-laden ceramic scaffold can potentially be used for bone regeneration.
Illite is a group of clay minerals that are expected to be widely used in catalyst fabrication, radioactive element adsorption, and so forth, due to its excellent adsorption properties. However, the ...shape control limitation of the illite product should be overcome to maximize its utilization and properties. We herein propose additive manufacturing (AM) as one of the best solutions to solve this structural drawback. Digital light processing (DLP) technology with the film‐type of the material supplying system was adapted instead of the general vat‐type DLP system to increase illite printability. The photo‐curability and printability of illite‐contained photocurable suspension were optimized. The color effect due to different ferric oxide content in yellow‐ and white‐illite which influence the photopolymerization process also adjusted thoroughly. White illite showed better photo‐curability and could be increased solid loading than yellow illite. The defect‐free illite products with three‐dimensional complex structures, which cannot be produced by typical ceramic processes, were obtained by DLP technology for both yellow‐ and white‐illite after sintering at 1100°C. The overcoming of shape control limitation of illites by ceramic AM proved in this study has excellent potential for expanding illite utilities in various applications.
A novel process was developed to fabricate core/shell-structured 3D scaffolds, made of calcium-deficient hydroxyapatite (CDHA) and alginate laden with pre-osteoblast MC3T3-E1 cells, through a ...combination of cement chemistry, dual paste-extruding deposition (PED), and cell printing. The cement reaction of calcium phosphates replaced the typical sintering process of the ceramic scaffold fabrication after the simultaneous printing of the ceramics and cell-laden hydrogel. The alginate crosslinking process was divided into two steps using different concentrations of CaCl
, during and after 3D printing, in order to obtain a stable 3D core/shell structure and high cell viability. The whole process was carried out under conditions (neutral pH and a temperature between room temperature and 37 °C) that were gentle to the cells, so the cells incorporated into the shell remained alive throughout the 3D scaffold for the entire culture period (35 days). The core/shell structured scaffold significantly enhanced the mechanical properties when compared with a hydrogel that uses a typical cell-printing process or with a ceramic scaffold, due to the co-operative effect of each material. The compressive strength of the CDHA/alginate scaffolds in the wet state was 3.2 MPa, whereas the compressive strength of alginate could not be determined in the wet state. The 3D structural morphology of CDHA/alginate scaffolds was well retained, even after a compression test, and showed less deformation because the CDHA ceramic-core was encapsulated within the elastic alginate. The process developed in this study suggests a new cell printing model that has excellent potential for application in the field of bone tissue regeneration.
Nano/microfibrous structure can induce high cellular activities because of the topological similarity of the extracellular matrix, and thus, are widely used in various tissue regenerative materials. ...However, the fabrication of a bioceramic (high weight percent)-based 3D microfibrous structure is extremely difficult because of the low process-ability of bioceramics. In addition, three-dimensional (3D) microfibrous structure can induce more realistic cellular behavior when compared to that of 2D fibrous structure. Hence, the requirement of a 3D fibrous ceramic-based structure is an important issue in bioceramic scaffolds. In this study, a bioceramic (α-TCP)-based scaffold in which the weight fraction of the ceramic exceeded 70% was fabricated using an electrohydrodynamic printing (EHDP) process. The fabricated ceramic structure consisted of layer-by-layered struts entangled with polycaprolactone microfibers and the bioceramic phase. Various processing conditions (such as applied electric field, flow rate, nozzle size, and weight fraction of the bioceramic) were manipulated to obtain an optimal processing window. A 3D printed porous structure was used as a control, which had pore geometry similar to that of a structure fabricated using the EHDP process. Various physical and cellular activities using preosteoblasts (MC3T3-E1) helped confirm that the newly designed bioceramic scaffold demonstrated significantly high metabolic activity and mineralization.
Abstract Mesoporous silica (MPS), synthesized via the supramolecular polymer templating method, is one of the most attractive nanomaterials for biomedical applications, such as drug delivery systems, ...labeling, and tissue engineering. The significant difference between MPS and general silica (colloidal silica) is the pore architectures, such as specific surface area and pore volume. The pore structures of nanomaterials have been considered to be one of the key conditions, causing nanotoxicity due to their different efficiency of cellular uptake and immune response. We first studied the influence of pore structural conditions of silica nanoparticles on both inflammation and apoptosis, in vitro and in vivo , by comparing MPS and colloidal silica, and defined underlying mechanisms of action. Both the MPS and colloidal silica nanoparticles are produced by almost similar synthetic conditions, except the use of polymer template for MPS. The specific surface area of colloidal silica and MPS was 40 and 1150 m2 g−1 , respectively, while other conditions, including particle size (100 nm) and shape (spherical), were kept constant. In both MTT assay and FACS analysis, MPS nanoparticles showed significantly less cytotoxicity and apoptotic cell death than colloidal silica nanoparticles. MPS nanoparticles induced lower expression of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6, in macrophages. The reduced inflammatory response and apoptosis elicited by MPS nanoparticles were resulting from the reduction of mitogen-activated protein kinases, nuclear factor-κB, and caspase 3. In addition, using the local lymph node assay, a standalone in vivo method for hazard identification of contact hypersensitivity, we showed that colloidal silica nanoparticles act as an immunogenic sensitizer and induce contact hypersensitivity but not MPS nanoparticles. In conclusion, the pore architecture of silica nanoparticles greatly influences their biocompatibility and should be carefully designed. The MPS nanoparticles exhibit better biocompatibility than colloidal silica and promise excellent potential usage in the field of biomedical and biotechnological applications.
We herein propose a novel low-temperature fabrication process of calcium deficient hydroxyapatite (CDHA) 3D scaffolds for bone tissue regeneration through a combination of material extrusion type 3D ...printing process and bone cement chemistry. The CDHA scaffolds with high porosity of 70% showed excellent mechanical property of 25 MPa (compressive strength), without any sintering process after 3D printing. By using this method, the final structures do not show size shrinkage, which must be considered in conventional ceramic sintering processes. We could therefore achieve both size- and 3D architecture-controlled porous CDHA scaffolds with high accuracy. In addition, the resulting ceramic cement scaffolds were not brittle and could be machined without chipping or fracturing the scaffold. The complete process takes place at physiological conditions (37 °C, pH=7), and heat sensitive drugs and biomolecules could be directly loaded onto the raw powder and achieve homogeneous distribution throughout the CDHA scaffold. In this study, we discuss various key factors to complete this low-temperature 3D printing fabrication of calcium phosphate, such as the pre-treatment conditions of particles, liquid-to-powder ratio, relationships between strut sizes, infill of structures, setting temperatures and the properties of 3D printed scaffolds. The low-temperature fabrication process of calcium phosphate scaffolds developed in this study has excellent potential for use in bone tissue engineering.
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Ceramic 3D printing based on stereolithography is an excellent alternative to overcome drawbacks of conventional subtractive manufacturing for 3D shape control. Optimization of photocurable ceramic ...slurry is one of the most essential conditions to achieve favorable 3D printed structures using SL. Homogeneity of ceramic particle dispersion in photocurable resin is particularly important to optimize ceramic suspension. Dispersant plays a significant role in increasing homogeneity. Dispersant in photocurable ceramic resin has an additional effect on photocurability and integrity of 3D printed green body. We herein discuss how dispersants influence 3D printing conditions based on stereolithography using various commercially available dispersants of BYK series such as BYK103, BYK111, BYK180, BYK182, and BYK2001. Both BYK111 and BYK180 showed better performances than others because of their lower volatilities under general temperature condition during a printing process. Both solubility and decomposition temperature of dispersants largely influenced the structural quality after washing and debinding processes. This study provides worthy information to design photocurable ceramic suspension for various types of ceramic materials.
Human-induced pluripotent stem cells (hiPSCs) can be applied in patient-specific cell therapy to regenerate lost tissue or organ function. Anisotropic control of the structural organization in the ...newly generated bone matrix is pivotal for functional reconstruction during bone tissue regeneration. Recently, we revealed that hiPSC-derived osteoblasts (hiPSC-Obs) exhibit preferential alignment and organize in highly ordered bone matrices along a bone-mimetic collagen scaffold, indicating their critical role in regulating the unidirectional cellular arrangement, as well as the structural organization of regenerated bone tissue. However, it remains unclear how hiPSCs exhibit the cell properties required for oriented tissue construction. The present study aimed to characterize the properties of hiPSCs-Obs and those of their focal adhesions (FAs), which mediate the structural relationship between cells and the matrix. Our in vitro anisotropic cell culture system revealed the superior adhesion behavior of hiPSC-Obs, which exhibited accelerated cell proliferation and better cell alignment along the collagen axis compared to normal human osteoblasts. Notably, the oriented collagen scaffold stimulated FA formation along the scaffold collagen orientation. This is the first report of the superior cell adhesion behavior of hiPSC-Obs associated with the promotion of FA assembly along an anisotropic scaffold. These findings suggest a promising role for hiPSCs in enabling anisotropic bone microstructural regeneration.
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Similar to calcium phosphates, magnesium phosphate (MgP) ceramics have been shown to be biocompatible and support favorable conditions for bone cells. Micropores below 25μm (MgP25), ...between 25 and 53μm (MgP53), or no micropores (MgP0) were introduced into MgP scaffolds using different sizes of an NaCl template. The porosities of MgP25 and MgP53 were found to be higher than that of MgP0 because of their micro-sized pores. Both in vitro and in vivo analysis showed that MgP scaffolds with high porosity promoted rapid biodegradation. Implantation of the MgP0, MgP25, and MgP53 scaffolds into rabbit calvarial defects (with 4- and 6-mm diameters) was assessed at two times points (4 and 8weeks), followed by analysis of bone regeneration. The micro-CT and histologic analyses of the 4-mm defect showed that the MgP25 and MgP53 scaffolds were degraded completely at 4weeks with simultaneous bone and marrow-like structure regeneration. For the 6-mm defect, a similar pattern of regeneration was observed. These results indicate that the rate of degradation is associated with bone regeneration. The MgP25 and MgP53 scaffold-implanted bone showed a better lamellar structure and enhanced calcification compared to the MgP0 scaffold because of their porosity and degradation rate. Tartrate-resistant acid phosphatase (TRAP) staining indicated that the newly formed bone was undergoing maturation and remodeling. Overall, these data suggest that the pore architecture of MgP ceramic scaffolds greatly influence bone formation and remodeling activities and thus should be considered in the design of new scaffolds for long-term bone tissue regeneration.
The pore structural conditions of scaffold, including porosity, pore size, pore morphology, and pore interconnectivity affect cell ingrowth, mechanical properties and biodegradabilities, which are key components of scaffold in bone tissue regeneration. In this study, we designed hierarchical pore structure of the magnesium phosphate (MgP) scaffold by combination of the 3D printing process, self-setting reaction and salt-leaching technique, and first studied the effect of pore structures of bioceramic scaffolds on bone tissue regeneration through both in vitro and in vivo studies (rabbit calvarial model). The MgP scaffolds with higher porosity promoted more rapid biodegradation and enhanced new bone formation and remodeling activities at the same time.
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