Biomedical subjects
Publications and source records attributed to Young Ku.
New bone formation on an RGD-containing oligopeptide-coated surface in vitro and in vivo was investigated. The surface showed two-fold higher osteoblastic cell adhesion and differentiation in vitro, and revealed statistically significant in vivo bone formation compared with the control (P < 0.05).
BACKGROUND: Recombinant human bone morphogenetic protein (rhBMP)-2 has been shown to stimulate significant regeneration of alveolar bone and cementum in periodontal defects clinically. The aim of this study was to evaluate the osteopromotive effect of oligopeptide domain-coated bovine bone mineral granules in a rabbit calvarial defect model. METHODS: The peptide-coated bovine bone was fabricated by incubating the graft material in a solution of oligopeptide domain. The cell attachment and proliferation were measured in vitro. Peptide-coated (test group) or uncoated (control group) bone minerals were implanted into 10-mm calvarial defects in rabbits, and the animals were sacrificed at 1, 2, or 4 weeks post-surgery. RESULTS: The cells grown with peptide-coated bone showed significantly higher proliferation activity at all times compared to cells grown with peptide-uncoated bone mineral. At 2 weeks post-surgery, the control wounds showed a limited amount of osteoid formation in a centripetal pattern around the grafted bone, but the oligopeptide domain-coated grafted bone had formed new bone around the grafted area. At 4 weeks post-surgery, the control sites showed increased new bone formation, but they still showed a significant difference from the peptide-coated bone-implanted sites. CONCLUSIONS: At 2 and 4 weeks, accelerated new bone formation was observed within the experimental sites compared to control groups. The use of deproteinized bovine bone combined with a synthetic oligopeptide seems to be a more beneficial material for bone regeneration in the early healing period.
Synthetic receptor binding motif mimicking bone morphogenetic protein-2 (BMP-2) was covalently linked to titanium (Ti) surfaces through a chemical conjugation process. The composition and properties of surface-modified Ti were investigated by XPS as well as by measuring surface radioactivity. In vitro tests were conducted with osteoblast-like MC3T3-E1 cells to assess cell attachment, morphology, and expression of osteogenic marker in the cells grown on modified Ti surfaces. In addition, in vivo experiments involved implants in mandibular bone defects of beagles to evaluate the effect of surface modification on bone regeneration. Results of XPS measurements showed a complete and homogeneous peptide overlayer on the Ti surfaces; the content was further measured by gamma counting. Biological evaluations showed that the biochemically modified Ti samples were active in terms of cell attachment behavior. The MC3T3-E1 cell growth rate, marker protein expression, and alkaline phosphatase production of the peptide-modified surfaces were all higher than those of control Ti. Importantly, the implants in the canine mandibles showed significant increase of bone growth when modified with bioactive peptide, thereby confirming that biochemical modifications of Ti surfaces can enhance the rate of bone healing as compared with untreated Ti surfaces.
The decomposition of 2-chlorophenol by UV/TiO2 process with the application of external bias voltage was examined in this study. Experiments were conducted in a batch reactor using TiO2-coated titanium sheet as anode and platinum sheet as cathode. The anode photocatalysis of 2-chlorophenol was totally inhibited for experiments conducted with the application of external anodic bias voltage lower than the flat band potential of TiO2. The decomposition rate of 2-chlorophenol was then increased with increasing external anodic bias voltage applied up to 0.0 V (versus SCE). The application of external bias voltage higher than 1.0 V did not markedly promote the photocatalysis of 2-chlorophenol possibly because the photocurrent induced was constant. Experimental results indicated that the decomposition of 2-chlorophenol was more effective for experiments conducted in acidic solutions due to the lower flat band potential of TiO2 and the higher photocurrent induced. The presence of electron scavengers in aqueous solution, such as oxygen molecules, may increase the decomposition rate of 2-chlorophenol. However, the effect of dissolved oxygen was diminished for experiments conducted with applied external bias voltage. The photocatalytic decomposition rate of 2-chlorophenol was enhanced linearly with the increasing UV light intensity when the external bias voltage was applied.
Photocatalytic processes using TiO(2) as a catalyst have attracted extensive attention for decomposition of organic contaminants. The determination of optimum reactor design and operational conditions are the major concerns for the development and potential application of the photocatalytic process. Various photoreactor types, photocatalyst arrangements, light sources, and operation conditions were reported. This study was focused on the application of the ultraviolet light emitting diode (UV-LED) as the UV light source for the photocatalytic decomposition of Reactive Red 22 (RR 22). The temporal behavior of the photocatalytic decomposition of RR 22 in aqueous solution by the UV-LED/TiO(2) with a rectangular planar fixed-film reactor operated in a recirculation mode was studied under various conditions including initial dye concentration, periodic illumination, light intensity, and arrangements of TiO(2) coating. The decomposition of RR 22 in aqueous solution by TiO(2) photocatalytic processes with the UV-LED was found to be technically feasible with a high TiO(2) coated weight (1.135g) and low pH value (pH 2). A Langmuir-Hinshelwood-type kinetic equation was adequate for modeling the photocatalytic decomposition of RR 22 by the UV-LED/TiO(2) photocatalytic processes. The experimental results indicated that the photonic efficiency with periodic illumination was much higher than those with continuous illumination. The photonic efficiencies with the quartz-liquid-catalyst (QLC) arrangement were higher than those with the quartz-catalyst-liquid (QCL) arrangement for experiments conducted at lower applied light intensity; however, the photonic efficiencies for these two arrangements were nearly identical for experiments conducted at higher light intensities.
BMP-2 (bone morphogenetic protein-2) has been used in promoting bone formation and, in combination with various delivery carriers, in bone regeneration or bone tissue-engineering practice. In the present study, BMP-2 was immobilized directly on a GBR (guided bone-regenerative) membrane surface made of chitosan nanofibres, providing a bioactive surface that can enhance bone-regeneration capacity. The BMP-2-conjugated membrane surface retained bioactivity for up to 4 weeks of incubation, as well as holding over 50% of the initial BMP-2 attached. The BMP-2-conjugated surface increased osteoblastic cell attachment in accordance with the amount of BMP-2 conjugated. In addition, the BMP-2-conjugated chitosan membrane significantly promoted cell proliferation, alkaline phosphatase activity, as well as calcium deposition when compared with BMP-2-adsorbed membrane, indicating a stable localization of BMP-2 at the surface of the chitosan membrane. Taking these findings together, the conjugation of BMP-2 on a chitosan nanofibrous membrane would seen to be applicable for inducing significant and localized bone formation in future GBR procedures.
The decomposition of 2-nitrophenol in aqueous solutions by ozone and UV/ozone processes was found to be technically feasible under adequate experimental conditions. Formation of nitrate ions was observed following the decomposition of 2-nitrophenol by ozone and UV/ ozone processes. Increasing ozone dosage and UV light intensity accelerated the decomposition rate of 2-nitrophenol in an aqueous solution. The species distribution of 2-nitrophenol under various solution conditions plays a significant role in determining decomposition behavior. In most experiments conducted in this study, the decomposition of 2-nitrophenol by ozone and UV/ozone processes was favored to occur in alkaline conditions. The addition of 2-butanol accelerated the rate of gaseous ozone transfer to an aqueous phase by reducing the surface tension of aqueous solution and therefore enhancing the decomposition rate of 2-nitrophenol by ozone and UV/ozone processes.
This study was designed to examine the sequential progress of healing, at two different time intervals, following delayed sinus augmentation using bovine hydroxyapatite (BHA) as the sole grafting material. Fourteen pairs of bone biopsies were taken from 10 patients after 6 and 12 months of healing, respectively. The biopsy specimens were examined histologically and histomorphometrically. The bone that was formed following sinus augmentation with BHA increased and matured over time up to 12 months after grafting; meanwhile, no overt signs of resorption of BHA were visible within the study period.
The favorable biological properties of silk fibroin (SF) nanofiber membrane make it a good candidate for clinical applications as a device in bone and periodontal regenerative therapy. The purpose of this study is to evaluate the biocompatibility of the SF nanofiber membrane, and to examine its effect on bone regeneration in a rabbit calvarial model. To examine the biocompatibility of the electrospun SF membrane, we investigated cell proliferation, morphology, and differentiation. The bone regenerative efficacy of the membrane was evaluated in the calvarial defect of rabbits. The cell numbers and osteocalcin production labels were significantly increased in accordance with culture period. Cells had a stellate shape and broad cytoplasmic extensions on the membrane. The cells showed activity of ALPase that was comparable to culture dishes, and were calcified similarly to culture dishes. In in vivo tests, a complete bony union across the defects was observed after 8 weeks. At 12 weeks, the defect had completely healed with new bone. In conclusion, the SF nanofiber membrane was shown to possess good biocompatibility with enhanced bone regeneration and no evidence of any inflammatory reaction. These results strongly suggest that the SF membrane should be useful as a tool for guided bone regeneration.
The surface of titanium implants is in direct contact with host tissue and plays a critical role in determining biocompatibility. Fibronectin (FN) and vitronectin (VN) are major cell adhesive proteins found in the extracellular matrix (ECM) of various tissues, and in circulating blood. The aim of this study was to evaluate the engineered biomimetic surface of titanium by using recombinant fragment of FN(8-10) and VN(NTD) that contains the binding site for integrins. MC3T3-E1 cells seeded upon the FN(8-10)-coated titanium showed a marked increase in cell adhesion, proliferation, and differentiation over VN(NTD)-coated titanium. In addition, we confirmed that the surface properties of titanium prefer for FN(8-10) over VN(NTD) (p<0.05) in protein adhesion. These results suggest that the FN(8-10)-modified titanium surface can be used to improve the osseointegration of titanium implants by enhancing bone formation.
The decomposition rates of several monochlorophenol by sonolysis were enhanced by the presence of hydrogen peroxide. An optimum concentration of hydrogen peroxide was observed for achieving maximum sonolysis rate of monochlorophenol. The decomposition rates of 3-chlorophenol by sonolysis were higher than those for 2- and 4-chlorophenol for most experiments conducted, suggesting that the ring structure of 3-chlorophenol provides more sites available for free radical attack. The temporal decomposition behavior of monochlorophenol in aqueous solutions is markedly influenced by the species distribution and the volatility of specific monochlorophenol.
BACKGROUND: Chitosan is known as a biodegradable and non-toxic natural polymer that enhances wound healing and bone formation. The aims of this study are to evaluate the biocompatibility of chitosan nanofiber membranes and to examine the effect of the chitosan nanofiber membranes on bone regeneration in rabbit calvarial defects. METHODS: In vitro cell proliferation tests using human osteosarcoma cell line MG63 and reverse transcription-polymerase chain reaction (RT-PCR) to evaluate the expression of alkaline phosphatase (ALP), collagen, osteocalcin (OCN), and GAPDH were done on chitosan nanofiber membranes. Chitosan nanofiber membranes were implanted in subcutaneous connective tissue and observed for 2, 4, and 6 weeks in rats. Ten-millimeter diameter round cranial defects were made in rabbits and covered by chitosan nanofiber membranes for 4 weeks. Specimens were decalcified and observed by a light microscope. RESULTS: MG63 cells proliferated for 28 days on the chitosan nanofiber membranes and expressed ALP, collagen, OCN, and GAPDH at 2 weeks. Chitosan nanofiber membranes that were grafted into rat subcutaneous tissue maintained their shape and space for bone regeneration for as long as 6 weeks. No inflammation could be seen on the membrane surface or in the surrounding tissues. In the rabbit calvarial defects, new bone filled the defects and fused to the original old bone in 4 weeks. CONCLUSIONS: The biocompatibility of the chitosan nanofiber membrane was confirmed, with enhanced bone regeneration and no evidence of an inflammatory reaction. This experiment shows that the novel biodegradable chitosan nanofiber membrane may be useful as a tool for guided bone regeneration.
An anodized surface significantly enhanced the adhesion of human osteoblast-like MG-63 cells to titanium. Using cDNA microarray analysis, five genes were differentially expressed while the rest remained unaltered. The results demonstrated that the anodized surface enhances cellular adhesion without significantly affecting the pattern of gene expression.
BACKGROUND: This study evaluated the efficacy and safety of a subantimicrobial dose of doxycycline (SDD) in conjunction with scaling and root planing (SRP). METHODS: The study was a 9-month, double masked, randomized, placebo-controlled, parallel-group trial. A total of 41 patients with moderate chronic periodontitis who received SRP were randomly allocated to receive either a doxycycline hyclate or a placebo 2 weeks after SRP. Clinical attachment level (CAL), the probing depth (PD), gingival crevicular fluid (GCF) levels, and matrix metalloproteinase (MMP)-8 and -13 levels were measured throughout the study. The effect of SDD in conjunction with SRP on the dynamics of the periodontal microflora was also assessed using dark-field microscopic and culture analysis. Information on adverse events was collected throughout the study. RESULTS: During the treatment period, per-patient reductions in PD and CAL were demonstrated for both treatment groups, with a significantly greater reduction for the SDD group. The mean value of per-patient change in the GCF was much greater for the SDD group. Microbial analysis showed there were a general tendency for cocci, non-motile rods, and aerobes to increase with increasing treatment duration and a general decreasing tendency for spirochetes, motile rods, and anaerobes and black pigmented bacteria in both treatment groups, but no significant difference between the groups. The MMP-8 and -13 levels of the SDD group gradually reduced with time, and the mean perpatient average was significantly higher than in the placebo group. The adverse events in the SDD group were similar to those in the placebo group. CONCLUSION: This study suggests that a submicrobial dose of doxycycline as an adjunct therapy with SRP might be safe and effective in the long-term management of chronic periodontitis.
BACKGROUND: Periodontal ligament (PDL) cells, connecting root cementum with alveolar bone, are important for periodontal wound healing. In order to obtain a predictable periodontal regeneration, selective adhesion and proliferation of PDL cells are essential. The purpose of this study was to investigate the effects of synthetic peptides mimicking cell-binding domain of fibronectin (FN) on human PDL cells. METHODS: Two types of oligopeptides, Gly3-Pro-His-Ser-Arg-Asn-Gly6-Arg-Gly-Asp-Gly (G3PHSRNG6RGDG) and Gly3-His-Pro-Asn-Arg-Ser-Gly6-Arg-Gly-Asp-Gly (G3HPNRSG6RGDG), were constructed using a solid-phase peptide synthesizer. Fibronectin type III ninth to tenth domain (FN III 9-10) and Arg-Gly-Asp-Ser (RGDS) were prepared for comparison with the effects of synthetic peptides. These peptides were coated onto 96-well cell culture plates with 0.001 approximately 100 microM concentrations. Cultured human PDL cells were then applied to the peptide-coated wells at a density of 1 x 10(4)/well. After 1 hour incubation at 37 degrees C, adhered cells were fixed, stained, and examined by phase contrast microscopy for cell spreading assay. Attached PDL cells were solubilized with 2% sodium dodecyl sulfate (SDS) for the cell attachment assay by measuring absorbance at 595 nm in microplate reader. Western blot analysis was performed to determine extracellular signal-regulated kinase (ERK1/2) activity. RESULTS: Cell attachment and spreading assays revealed that G3PHSRNG6RGDG (> or = 10 microM) possesses similar adhesive behavior to FN III 9-10. G3PHSRNG6RGDG showed a comparable ERK1/2 activity when compared to FN III 9-10. CONCLUSIONS: G3PHSRNG6RGDG enhanced an attachment and spreading of human PDL cells thereby increasing ERK1/2 activity. Taken together, it is anticipated that this peptide might be a potential tool for arranging a biologically attractive environment for PDL cells, which would enhance periodontal regeneration efficacy.
Photocatalytic decomposition of gaseous benzene at room temperature was studied with a fixed-bed annular reactor using titania as the photocatalyst. The effects of humidity, UV light intensity and benzene concentration on the conversion and mineralization of benzene were presented. Experimental results can be adequately described by using the Langmuir-Hinshelwood (L-H) kinetic model. The concentration distribution of benzene in the annular reactors of various dimensions can be described by combining the reactor design equation with L-H kinetics. Deactivation of catalyst was observed and attributed to the adsorption of reaction intermediates on TiO2 surface. The deactivated TiO2 catalyst could be photochemically regenerated by ozone-purging in the presence of humidity.
The light delivery and distribution phenomena along the optical fiber coated with the P-25 TiO(2) particles by dipping was investigated. The surface properties (coverage, roughness and thickness) of the TiO(2) layer coated on the optical fiber were characterized by SEM micrographs. For TiO(2) layer prepared from solutions containing less than 20 wt.% of TiO(2) slurry, the thickness of layer was increased linearly with the TiO(2) slurry content in solutions. The UV light intensity transmitted along a TiO(2)-coated optical fiber decreased more rapidly than that transmitted along a non-coated fiber. Based on the experimental results, the light intensity distribution around a coated optical fiber was modeled to determine the optimum configuration for the design of optical fiber reactors under various operational conditions.
A fibronectin fragment, which spans from the ninth to tenth type III domain, showed > 95% biological activity in promoting osteoblast adhesion, proliferation and differentiation level compared with those of native fibronectin (FN) molecule. This suggests that the FN type III ninth-tenth domain fragment serves a good substitute for native FN in biomimetic application for osteogenesis.