Papers by Author: Dong Woo Cho

Abstract: Although tissue engineering is an area with great potential, it still has few applications due to the lack of biocompatible, biodegradable materials with suitable mechanical properties. Recently, several biodegradable materials were developed, of which poly(propylene fumarate (PPF) is one of the most notable. It degrades into fumaric acid and propylene glycol, which are both biocompatible products. Microstereolithography is a new technology that can be used to fabricate free-form 3-D microstructures by dividing a desired shape into many slices of a given horizontal thickness. This technology requires a low-viscosity resin to fabricate fine structures. However, the viscosity of PPF is too high to fabricate 3D structures using microstereolithography. Therefore, we reduced the viscosity of the resin by adding diethyl fumarate (DEF). Then, we added a photoinitiator to photo-crosslink the DEF/PPF resin, and fabricated 2.5-D scaffolds using our system. We confirmed that microstereolithography technology is effective in scaffold fabrication. The fabricated 2.5-D scaffolds were seeded with fibroblasts and the cells attached well after seeding.

Abstract: This paper compares the characteristics of chondrocyte adhesion on two types of threedimensional (3-D) scaffold: types A and B. These 3-D scaffolds can be repeatedly constructed with the same dimensions using microstereolithography, a system that allows the fabrication of predesigned internal structures, such as pore size and porosity, by stacking the photopolymerized material. In tissue engineering, chondrocyte adhesion to a scaffold should have a major effect on the regeneration of cartilage. In this regard, we evaluated chondrocyte adhesion to two types of scaffold and found that chondrocyte adhesion was better on the type B scaffold than on the type A, demonstrating the importance of scaffold geometry in chondrocyte adhesion.

Abstract: We fabricated micro-patterned 2.5-D scaffolds using micro-end-milling with controlled pore and island sizes and interconnectivity to determine the effects of the micro-patterns on the cell culturing process. Micro-end-milling can easily realize a high aspect ratio and accuracy, and can be applied to various materials, including those that are biocompatible and biodegradable. Sixteen types of micro-patterned scaffolds were designed and fabricated using the micro-end-milling process. Fibroblasts were seeded and cultured to examine the viability of the developed micropatterned scaffolds and their absorbed cell adhesion. The results confirmed that the fabricated micro-patterns functioned successfully as scaffolds.

Abstract: In this study, we investigated the effect of the use of alginate sponge as a chondrocyte-3D scaffold for the construction of a cartilage graft. Alginate sponge was made by 5% alginic acid which was crosslinked by CaCl2. Chondrocytes were obtained from a nasal septum after the operation and cultured in 3D alginate sponge. For analysis of cell differentiation, we have checked aggrecan, collagen type I and II using RT-PCR and performed the histological and scanning electron microscopy analysis. Our experiments showed that alginate sponge of 5% promoted sufficient chondrocyte proliferation and differentiation, resulting in the formation of a specific cartilage matrix. The sponge presents new perspectives with respect to in vitro production of "artificial" cartilage. We conclude that the alginate sponges have potential as a scaffold for cartilage tissue engineering.

Abstract: Understanding chondrocyte behavior inside complex, three-dimensional environments with controlled patterning of geometrical factors would provide significant insights into the basic biology of tissue regenerations. One of the fundamental limitations in studying such behavior has been the inability to fabricate controlled 3D structures. To overcome this problem, we have developed a three-dimensional microfabrication system. This system allows fabrication of predesigned internal architectures and pore size by stacking up the photopolymerized materials. Photopolymer SL5180 was used as the 3D microfabricated scaffolds. The results demonstrate that controllable and reproducible inner-architecture can be fabricated. Chondrocytes from human nasal septum were cultured in 3D scaffolds for cell adhesion behavior. Such 3D scaffolds might provide effective key factors to study cell behavior in complex environments and could eventually lead to optimum design of scaffolds in various tissue regenerations such as cartilage, bone, etc. in a near future.

Abstract: For effective rough milling, an optimized criterion is required to select the feedrate. In this study, a method to obtain the most appropriate reference cutting force for rough milling was developed. The reference cutting force was determined by considering the transverse rupture strength of the tool material and the area of the rupture surface. A finite element method analysis was performed to accurately calculate the area of the rupture surface. Using the analyzed results, the effect of various cutting parameters on the chipping phenomenon was determined. The calculation method for the reference cutting force considered the area of the rupture surface, the effect of the rake angle, and the axial depth of cut. The experimental results clearly show that the reference cutting force obtained from the proposed method met the desired constraints.