Papers by Author: Byung Ju Choi

Abstract: The effect of anodic oxide films produced by β-glycerophosphate (β-GP) and calcium acetate (CA) anodizing on osteoblast-like cell attachment and spreading were evaluated in this study. Anodic oxide films were produced in different conditions: Group 1, 0.02 M β-GP and 0.2 M CA; Group 2, 0.03 M β-GP and 0.2 M CA; Group 3, 0.03 M β-GP and 0.2 M CA. Anodic oxide surface was significantly rougher in comparison to the control untreated titanium surfaces, and the surface roughness and composition of phosphate and oxide increased as the concentration of β-GP was increased. There was no significant difference in the cell viability when cells were cultured on the control or anodized surface using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Scanning electron micrographs revealed more spread cells on the anodized surface than on the smooth control surface. In conclusion, we suggested that the positive effects of anodized surfaces produced by β-GP and CA on spreading of osteoblast-like cells may be the result of the difference of surface roughness and amount of Ca and P in the oxide layer.

Abstract: The response of osteoblast-like cells cultured on blasted and/or acid etching surfaces and the influence of surface texture or microtopography on cell attachment, cell proliferation, and the gene expression of the osteoblastic phenotype using ROS 17/2.8 cell lines were evaluated. The blasted and/or acid etching surfaces were significantly rougher in comparison to machined and etched surfaces (p < 0.05). On X-ray diffraction analysis, titanium hydride (TiH2) was observed on the surface etched with a mixture of HCl-H2SO4 solution, whereas TiH2 was not observed on machined and blasted surfaces. After 24 h incubation, most of the cells of all the groups had a flattened, polygonal shape and were fully spread, exhibiting the onset of proliferation. The MTT assay showed a significant decrease on the blasted surface compared to the machined surface at 7 day culture (p < 0.05). The expression of osteopontin mRNA, α1 (I) collagen mRNA, and alkaline phosphatase mRNA on rough surfaces was higher than on the machined surfaces, and was highest on the blasted surface at day 7.

Abstract: This study was performed to evaluate the effect of anorganic bone mineral (ABM) coated with Tetra-Cell Adhesion Molecule (T-CAM) for bone formation in rabbit calvarial defects and compare the capability of bone formation in ABM coated with T-CAM (ABM/T-CAM) to that in commercially available ABM coated with a synthetic peptide (P-15) which mimics the cell-binding domain of type I collagen, PepGen P-15TM. T-CAM composed of four cell adhesion molecules (RGD, PHSRN, EPDIM, and YH) was synthesized and ABM/T-CAM were prepared by absorbing T-CAM on ABM (OsteoGraf/N-300; Densply Friadent Ceramed Corp., USA). Two 9-mm diameter, full-thickness calvarial defects were made in each rabbit parietal bone and sixteen adult male rabbits were used in this experiment. The defects were reconstructed according to four treatment groups: unfilled, BM-grafted, PepGen P-15TM-grafted, and ABM/T-CAM-grafted. The animals were sacrificed at 2 and 4 weeks after surgery for histologic and histomorphometric evaluation. An active new bone formation were observed in the defects of ABM/T-CAM and PepGen P-15TM grafted groups at 2 and 4 weeks of healing in histologic observation. The results of histomorphometric analysis revealed higher new bone formation in ABM/T-CAM-grafted (14.62±0.6% at 2 weeks, 15.33±2.4% at 4 weeks) and PepGen P-15TM-grafted (12.46±1.0% at 2 weeks, 18.14±1.7% at 4 weeks) groups than in unfilled control (7.03±2.3% at 2 weeks, 8.71±3.4% at 4 weeks) and ABMgrafted (6.59±1.7% at 2 weeks, 9.25±0.8% at 4 weeks) groups at 2 and 4 weeks of healing with statistical significance (P<0.01). The results of this study indicated that the immobilizing T-CAM on ABM enhances the capability of bone substitutes to serve as an effective habitat for bone forming cells in vivo. In conclusion, we suggested that this composite graft material, ABM/T-CAM may be served as an effective tissue-engineered bone graft material in osseous reconstructive surgery.

Abstract: The objective of this study was to evaluate the biocompatibility and effects of the particulated and surface modified Ostrich eggshell (OES) as bone graft substitutes in healing of calvarial defects in rats. Additionally we compared the bone forming ability of the surface modified OES to that of BioCoral (Inoteb, France), which has the same chemical compositions as OES, calcium carbonate (CaCO3). Surface modified OES particles were fabricated by alkaline etching (microroughened-OES) and biomimetic calcium phosphate coating (CaP coated-OES). 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to evaluate cell viability at 1, 4, and 7days using ROS 17/2.8 cells, a rat osteosarcoma cell line. To evaluate the bone forming ability, surface modified OES and BioCoral were filled in the calvarial defects of fourteen adult male Sprague-Dawley rats. After 4 weeks of healing, animals were sacrificed and evaluated histologically and histomorphometrically. The MTT assay indicated the increases in viable cell numbers of all groups according to the time, and significantly increased cell numbers were observed on CaP coated-OES and BioCoral at 7 day (P<0.01). The histomorphometric results showed that significantly increased amount of new bone formation in the microroughened-OES, CaP coated-OES, and BioCoral grafted defects compared with unfilled defects (P<0.0001). The degree of ossification was most prominent in CaP coated-OES grafted defects. The results of this study suggest that surface modified OES particles are biocompatible and yield favorable bone formation in rat calvarial defects. In conclusion, surface modified OES grafts may be considered as effective osteoconductive grafting materials, but further studies are needed to produce more optimal surface modification and confirm long-term results.