[Show abstract][Hide abstract] ABSTRACT: Due to its simplicity and effectiveness, the physical blending of polymers is considered to be a practical strategy for developing a versatile scaffold having desirable mechanical and biochemical properties. In the present work, an indirect three-dimensional (i3D) printing technique was proposed to fabricate a 3D free-form scaffold using a blend of immiscible materials, such as polycaprolactone (PCL) and gelatin. The i3D printing technique includes 3D printing of a mold and a sacrificial molding process. PCL/chloroform and gelatin/water were physically mixed to prepare the blend solution, which was subsequently injected into the cavity of a 3D printed mold. After solvent removal and gelatin cross-linking, the mold was dissolved to obtain a PCL-gelatin (PG) scaffold, with a specific 3D structure. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis indicated that PCL masses and gelatin fibers in the PG scaffold homogenously coexisted without chemical bonding. Compression tests confirmed that gelatin incorporation into the PCL enhanced its mechanical flexibility and softness, to the point of being suitable for soft-tissue engineering, as opposed to pure PCL. Human adipose-derived stem cells, cultured on a PG scaffold, exhibited enhanced in vitro chondrogenic differentiation and tissue formation, compared with those on a PCL scaffold. The i3D printing technique can be used to blend a variety of materials, facilitating 3D scaffold fabrication for specific tissue regeneration. Furthermore, this convenient and versatile technique may lead to wider application of 3D printing in tissue engineering.
[Show abstract][Hide abstract] ABSTRACT: One of the main issues in tissue engineering has been the development of a three-dimensional (3D) structure, which is a temporary template that provides the structural support and microenvironment necessary for cell growth and differentiation into the target tissue. In tissue engineering, various biomaterials and their processing techniques have been applied for the fabrication of 3D structures. In particular, 3D printing technology enables the fabrication of a complex inner/outer architecture using a computer-aided design and manufacturing (CAD/CAM) system, and it has been widely applied to the fabrication of 3D structures for tissue engineering. Novel cell/organ printing techniques based on 3D printing have also been developed for the fabrication of a biomimetic structure with various cells and biomaterials. This paper presents a comprehensive review of the functional scaffold and cell-printed structures based on 3D printing technology and the application of this technology to various kinds of tissues regeneration.
No preview · Article · Oct 2014 · Transactions of the Korean Society of Mechanical Engineers B
[Show abstract][Hide abstract] ABSTRACT: One of the major issues in tissue engineering has been the development of three-dimensional (3D) scaffolds, which serve as a structural template for cell growth and extracellular matrix formation. In scaffold-based tissue engineering, 3D printing (3DP) technology has been successfully applied for the fabrication of complex 3D scaffolds by using both direct and indirect techniques. In principle, direct 3DP techniques rely on the straightforward utilization of the final scaffold materials during the actual scaffold fabrication process. In contrast, indirect 3DP techniques use a negative mold based on a scaffold design, to which the desired biomaterial is cast and then sacrificed to obtain the final scaffold. Such indirect 3DP techniques generally impose a solvent-based process for scaffold fabrication, resulting in a considerable increase in the fabrication time and poor mechanical properties. In addition, the internal architecture of the resulting scaffold is affected by the properties of the biomaterial solution. In this study, we propose an advanced indirect 3DP technique using projection-based micro-stereolithography and an injection molding system (IMS) in order to address these challenges. The scaffold was fabricated by a thermal molding process using IMS to overcome the limitation of the solvent-based molding process in indirect 3DP techniques. The results indicate that the thermal molding process using an IMS has achieved a substantial reduction in scaffold fabrication time and has also provided the scaffold with higher mechanical modulus and strength. In addition, cell adhesion and proliferation studies have indicated no significant difference in cell activity between the scaffolds prepared by solvent-based and thermal molding processes.
[Show abstract][Hide abstract] ABSTRACT: Artificial tracheal grafts should have not only enough compressive strength to maintain an open tracheal lumen, but also sufficient flexibility for stable mechanical behavior, similar to the native trachea at the implant site. In this study, we developed a new 3D artificial tracheal graft using a bellows design for considering its mechanical behavior. To investigate the mechanical behavior of the bellows structure, finite element method (FEM) analysis in terms of longitudinal tension/compression, bending and radial compression was conducted. The bellows structure was then compared with the cylinder structure generally used for artificial tracheal grafts. The FEM analysis showed that the bellows had outstanding flexibility in longitudinal tension/compression and bending. Moreover, the bellows kept the lumen open without severe luminal deformation in comparison with the cylinder structure. A three-dimensional artificial tracheal graft with a bellows design was fabricated using indirect solid freeform fabrication technology, and the actual mechanical test was conducted to investigate the actual mechanical behavior of the bellows graft. The fabricated bellows graft was then applied to segmental tracheal reconstruction in a rabbit model to assess its applicability. The bellows graft was completely incorporated into newly regenerated connective tissue and no obstruction at the implanted site was observed for up to 8 weeks after implantation. The data suggested that the developed bellows tracheal graft could be a promising alternative for tracheal reconstruction.
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stromal cells (MSCs) are multipotent progenitor cells in adult tissues. Current challenges for the clinical application of MSCs include donor site morbidity, which underscores the need to identify alternative sources of MSCs. This study aimed to explore potential new sources of multipotent MSCs for use in tissue regeneration and the functional restoration of organs.
Mixed methods research.
Tertiary care center.
The authors isolated MSCs from human inferior turbinate tissues discarded during turbinate surgery of 10 patients for nasal obstruction. The expression of surface markers for MSCs was assessed by fluorescence-activated cell sorting. The differentiation potential of human turbinate mesenchymal stromal cells (hTMSCs) was analyzed by immunohistochemistry, reverse transcriptase-polymerase chain reaction, and Western blot analysis.
Surface epitope analysis revealed that hTMSCs were negative for CD14, CD19, CD34, and HLA-DR and positive for CD29, CD73, and CD90, representing a characteristic phenotype of MSCs. Extracellular matrices with characteristics of cartilage, bone, and adipose tissue were produced by inducing the chondrogenic, osteogenic, and adipogenic differentiation of hTMSCs, respectively. The expression of neuron-specific markers in hTMSCs was confirmed immunocytochemically.
The hTMSCs represent a new source of multipotent MSCs that are potentially applicable to tissue engineering and regenerative medicine. The availability of differentiated adult cells will allow the development of an effective tissue regeneration method.
No preview · Article · May 2012 · Otolaryngology Head and Neck Surgery
[Show abstract][Hide abstract] ABSTRACT: Projection-based stereolithography (pSL) is a powerful technique for fabricating three-dimensional (3-D) freeform structures. This study developed a new pixel-based solidification model for pSL to predict the patterning results. pSL technology makes it possible to create a two-dimensional (2-D) pattern in a single exposure, using a dynamic mask capable of generating 2-D images with micro-resolution. Then, a 3-D structure can be fabricated by stacking the 2-D patterns. Therefore, pixel-based modeling is crucial for predicting the patterning results because the pixel is the fundamental component of the illuminated 2-D images in the patterning process. This study constructed a mathematical model to describe the intensity distribution of an illuminated image. The model was used to predict solidified shapes by calculating the exposure energy and compared with patterning results. The findings showed that our model is quite useful for estimating fabrication results obtained using pSL technology.
No preview · Article · May 2012 · Sensors and Actuators A Physical
[Show abstract][Hide abstract] ABSTRACT: Microstereolithography (MSTL) is a SFF technology that has been used to fabricate 3-D scaffolds in tissue engineering. Projection-based microstereolithography (pMSTL) offers the advantage of increased fabrication speed compared with a line-scan-based MSTL by creating 2-D patterns with single-section image exposure and then stacking them. To fabricate a complex 3-D structure for a target tissue (liver, blood vessel, etc.) using the pMSTL system, we introduce a new algorithm that automatically generates projection image information. The procedure uses the STL file format as the raw data for a 3-D model. First, the STL file data are converted into slicing data composed of closed loops, including layer thicknesses. Projection image data are then generated from the closed loops calculated during the slicing process. Finally, the projection image data are converted into pixel information. The proposed technique is evaluated by fabricating a complex 3-D vascular network structure, and is shown to be quite practical for automated fabrication of complex 3-D structures in tissue engineering.
Full-text · Article · Mar 2012 · International Journal of Precision Engineering and Manufacturing
[Show abstract][Hide abstract] ABSTRACT: Scaffolds play an important role in the regeneration of artificial tissues or organs. A scaffold is a porous structure with a micro-scale inner architecture in the range of several to several hundreds of micrometers. Therefore, computer-aided construction of scaffolds should provide sophisticated functionality for porous structure design and a tool path generation strategy that can achieve micro-scale architecture. In this study, a new unit cell-based computer-aided manufacturing (CAM) system was developed for the automated design and fabrication of a porous structure with micro-scale inner architecture that can be applied to composite tissue regeneration. The CAM system was developed by first defining a data structure for the computing process of a unit cell representing a single pore structure. Next, an algorithm and software were developed and applied to construct porous structures with a single or multiple pore design using solid freeform fabrication technology and a 3D tooth/spine computer-aided design model. We showed that this system is quite feasible for the design and fabrication of a scaffold for tissue engineering.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to maximize oxygen diffusion within a three-dimensional scaffold in order to improve cell viability and proliferation. To evaluate the effect of pore architecture on oxygen diffusion, we designed a regular channel shape with uniform diameter, referred to as cylinder shaped, and a new channel shape with a channel diameter gradient, referred to as cone shaped. A numerical analysis predicted higher oxygen concentration in the cone-shaped channels than in the cylinder-shaped channels, throughout the scaffold. To confirm these numerical results, we examined cell proliferation and viability in 2D constructs and 3D scaffolds. Cell culture experiments revealed that cell proliferation and viability were superior in the constructs and scaffolds with cone-shaped channels.
No preview · Article · Oct 2010 · Journal of Biomechanical Engineering
[Show abstract][Hide abstract] ABSTRACT: We developed a hybrid scaffold and a bioreactor for cartilage regeneration. The hybrid scaffold was developed as combination
of two components: a biodegradable framework and hydrogel-containing chondrocytes. We performed the MTT cell proliferation
assay to compare the proliferation and viability of chondrocytes on three types of scaffolds: an alginate gel, the hybrid
scaffold, and an alginate sponge. Cells were encapsulated in 2% agarose gel. The bioreactor consisted of a circulation system
and a compression system. We performed dynamic cell culture on these agarose gels in the bioreactor for 3 days.
Full-text · Article · Oct 2009 · Chinese Science Bulletin
[Show abstract][Hide abstract] ABSTRACT: Mechanical stimulation plays a role in improving cell growth in the skeletal system. Many studies have reported the development of bioreactors to stimulate cell-seeded, three-dimensional scaffolds. In this study, we developed a bioreactor capable of applying controlled compression to a cell-seeded agarose hydrogel. This bioreactor consists of a circulation system and compression system. In the circulation system, the culture chamber was sealed to prevent contamination and a pump circulated the medium. In the compression system, mechanical stimuli were controlled by LabVIEW software and a mechanical transfer system. To compare the effects of mechanical stimulation on agarose hydrogel scaffolds, we cultured MC3T3-E1 cells statically and dynamically. The number of cells was increased by 43% at seven days under the intermittent condition than under the static conditions.
No preview · Article · Apr 2009 · Microelectronic Engineering