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ABSTRACT: Magnesium and its alloys are candidate materials for biodegradable implants; however, excessively rapid corrosion behavior restricts their practical uses in biological systems. For such applications, surface modification is essential, and the use of anticorrosion coatings is considered as a promising avenue. In this study, we coated Mg with hydroxyapatite (HA) in an aqueous solution containing calcium and phosphate sources to improve its in vitro and in vivo bio-corrosion resistance, biocompatibility and bone response. A layer of needle-shaped HA crystals was created uniformly on the Mg substrate even when the Mg sample had a complex shape of a screw. In addition, a dense HA-stratum between this layer and the Mg substrate was formed. This HA coating layer remarkably reduced the corrosion rate of the Mg tested in a simulated body fluid. Moreover, the biological response, including cell attachment, proliferation and differentiation, of the HA-coated samples was enhanced considerably compared to samples without a coating layer. The preliminary in vivo experiments also showed that the bio-corrosion of the Mg implant was significantly retarded by HA coating, which allowed for good mechanical stability. In addition, in the case of the HA-coated implants, biodegradation was mitigated, particularly over the first six weeks of implantation. This considerably promoted bone growth at the interface between the implant and bone. These results confirmed that HA-coated Mg is a promising material for biomedical implant applications.
Journal of Biomedical Materials Research Part A 03/2013; · 2.63 Impact Factor
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ABSTRACT: Hydroxyapatite was deposited on pure magnesium (Mg) with a flexible poly(ε-caprolactone) interlayer to reduce the corrosion rate of Mg and enhance coating flexibility. The poly(ε-caprolactone) interlayer was uniformly coated on Mg by a spraying method, followed by hydroxyapatite deposition on the poly(ε-caprolactone) using an aerosol deposition method. In scanning electron microscopy observations, inorganic/organic composite-like structure was observed between the hydroxyapatite and poly(ε-caprolactone) layers, resulting from the collisions of hydroxyapatite particles into the poly(ε-caprolactone) matrix at the initial stage of the aerosol deposition. The corrosion resistance of the coated Mg was examined using potentiodynamic polarization tests. The hydroxyapatite/poly(ε-caprolactone) double coating remarkably improved the corrosion resistance of Mg in Hank's solution. In the in vitro cell tests, the coated Mg showed better cell adhesion compared with the bare Mg due to the reduced corrosion rate and enhanced biocompatibility. The stability and flexibility of hydroxyapatite/poly(ε-caprolactone) double coating was investigated by scanning electron microscopy inspections after the coated Mg was deformed. The hydroxyapatite coating on the poly(ε-caprolactone) interlayer revealed enhanced coating stability and flexibility without cracking or delamination during bending and stretching compared with the hydroxyapatite single coating. These results demonstrated that the hydroxyapatite/poly(ε-caprolactone) double coating significantly improved the surface corrosion resistance of Mg and enhanced coating flexibility for use of Mg as a biodegradable implant.
Journal of Biomaterials Applications 12/2012; · 2.08 Impact Factor
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ABSTRACT: This study investigated the utility of poly(ether imide) (PEI) coating for improving the corrosion resistance and biocompatibility of magnesium (Mg) implants for orthopedic application. In particular, the microstructure of the PEI coating layers was controlled by the adjustment of the temperature used to dry the spin-coated wet PEI films. When a wet PEI film was dried at 4°C, a relatively thick and porous coating layer was achieved as a result of an extensive exchange of the solvent with water in a moist environment. In contrast, when a wet PEI film was dried at 70°C, a relatively thin and dense layer was created due to the faster evaporation of the solvent with a negligible exchange of the solvent with water. The porous PEI coating layer showed higher stability than did the dense one when immersed in a simulated body fluid (SBF), which was presumably attributed to the formation of chemical bonding between the PEI and the Mg substrate. Both the porous and the dense PEI coated Mg specimens showed significantly improved in vitro biocompatibility, which were assessed in terms of cell attachment, proliferation and differentiation. However, interestingly, the dense PEI coating layer showed greater cell proliferation and differentiation than did the porous layer. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.
Journal of Biomedical Materials Research Part A 11/2012; · 2.63 Impact Factor
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ABSTRACT: Nanofibrous membranes, consisting of a poly(L-lactic acid) (PLLA)-silica xerogel hybrid material, were successfully fabricated from a hybrid sol using the electrospinning technique for guided bone regeneration (GBR) application. These hybrid nanofibers exhibited a homogeneous and continuous morphology, with a nano-sized dispersed silica xerogel phase in the PLLA fiber matrix. The mechanical properties, such as the tensile strength and the elastic modulus, were improved as the silica xerogel content increased up to 40%. All of the hybrid membranes exhibited highly hydrophilic surfaces and good proliferation levels. After culturing for 13 days, the cells that were cultured on the hybrid membranes exhibited a significantly higher ALP activity compared to the pure PLLA membrane. Moreover, the in vivo animal experiments that used the rat calvarial defect model revealed a remarkably improved bone regeneration ability for the hybrid membrane compared to pure PLLA. These results demonstrated the feasibility of these hybrid membranes for efficient GBR. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.
Journal of Biomedical Materials Research Part B Applied Biomaterials 11/2011; · 2.15 Impact Factor
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ABSTRACT: Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF(2) interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF(2) and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF(2) coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF(2) interlayer could be used as a potential candidate for biodegradable implant materials.
Journal of Materials Science Materials in Medicine 09/2011; 22(11):2437-47. · 2.32 Impact Factor
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ABSTRACT: Oxide coating layers were formed on a pure magnesium (Mg) substrate through anodization and micro-arc oxidation (MAO) in order to enhance the biocompatibility and reduce the degradation rate. A thin, smooth MgO coating layer was formed after the anodization. On the other hand, when the Mg was treated using the MAO process, a relatively thick, rough MgO layer was formed. The corrosion properties were investigated using electrochemical and ion release tests in a simulated body fluid. Both the anodization and the MAO treatment enhanced the corrosion resistance of the Mg specimens. However, the MgO layers that formed on the surface were not stable enough to render favorable environments for cell growth. The anodized and MAO-treated specimens were post-treated in a cell-culturing medium in order to improve the stability of the coating layer. The biocompatibility was evaluated using in vitro cell tests, including cell attachment, DNA measurement, and alkaline phosphatase (ALP) activity tests. The DNA levels of the surface-treated Mg were about 6-10 times higher than the bare Mg. The ALP activity levels were also more than double after either the anodization or the MAO followed by the post-treatments. These results demonstrated that the biocompatibility and the corrosion resistance of Mg were significantly improved by the series of surface treatments.
Journal of Biomaterials Applications 08/2011; · 2.08 Impact Factor
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ABSTRACT: In this study, a poly(epsilon-caprolactone) (PCL)/bioactive glass (BG) nanocomposite was fabricated using BG nanofibers (BGNFs) and compared with an established composite fabricated using microscale BG particles. The BGNFs were generated using sol-gel precursors via the electrospinning process, chopped into short fibers and then incorporated into the PCL organic matrix by dissolving them in a tetrahydrofuran solvent. The biological and mechanical properties of the PCL/BGNF composites were evaluated and compared with those of PCL/BG powder (BGP). Because the PCL/BG composite containing 20 wt % BG showed the highest level of alkaline phosphatase (ALP) activity, all evaluations were performed at this concentration except for that of the ALP activity itself. In vitro cell tests using the MC3T3 cell line demonstrated the enhanced biocompatibility of the PCL/BGNF composite compared with the PCL/BGP composite. Furthermore, the PCL/BGNF composite showed a significantly higher level of bioactivity compared with the PCL/BGP composite. In addition, the results of the in vivo animal experiments using Sprague-Dawley albino rats revealed the good bone regeneration capability of the PCL/BGNF composite when implanted in a calvarial bone defect. In the result of the tensile test, the stiffness of the PCL/BG composite was further increased when the BGNFs were incorporated. These results indicate that the PCL/BGNF composite has greater bioactivity and mechanical stability when compared with the PCL/BG composite and great potential as a bone regenerative material.
Journal of Biomedical Materials Research Part B Applied Biomaterials 06/2009; 91(1):213-20. · 2.15 Impact Factor
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ABSTRACT: Currently there is no consensus on which staging system is the best in predicting the survival of patients with hepatocellular carcinoma (HCC). The aim of this study was to identify independent factors to predict survival and to compare 4 available prognostic staging systems in patients with early HCC after radiofrequency ablation.
We retrospectively studied 100 Korean patients with early HCC. Prognostic factors for survival were analysed by univariate and multivariate analysis using the Kaplan-Meier method and Cox proportional hazard regression models. Okuda, Cancer of the Liver Italian Program (CLIP), TNM and Japanese integrated staging score (JIS score) were evaluated before the treatments.
Overall survival rates of 12, 24 and 36 months were 89%, 76%, and 64% respectively and the mean survival duration was 45 months. Multivariable analysis showed that albumin, total bilirubin and size of tumor were independent prognostic factors. Multivariate analysis showed that TNM and JIS score staging systems were significant staging systems for the prediction of prognosis.
Both TNM and JIS score are more effective than the Okuda and CLIP staging systems in stratifying patients into different risk groups with early HCC. However, JIS score gives better prediction of prognosis in patients with HCC after radiofrequency ablation.
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi 02/2007; 49(1):17-23.
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ABSTRACT: Benign metastasizing leiomyoma (BML) is composed of well-differentiated smooth muscle cells and dense connective tissue. BML affects middle-aged women who have had previous hysterectomies due to a histologically benign-appearing uterine leiomyoma. We report here on a case of BML from the uterine leiomyoma in a 39-year-old woman that involved the soft tissues, skeletal muscles, lungs and breasts. She underwent a hysterectomy for the uterine leiomyoma, double oophorectomy for hormonal ablation and lung wedge resection to confirm the diagnosis. The microscopic findings of the breast and lung tumor were similar to those of the benign uterine leiomyoma. Therefore, we consider that these lesions were breast and pulmonary metastases of the uterine leiomyoma. We report here on a rare case of benign metastasizing uterine leiomyoma that involved the soft tissue, skeletal muscles, lungs and breasts, and we include a review of the relevant literature.
The Korean Journal of Internal Medicine 10/2006; 21(3):199-201.
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Gi Hoon Son,
Dongho Geum,
Sooyoung Chung,
Eun Joo Kim, Ji-Hoon Jo,
Chang-Mee Kim,
Kun Ho Lee,
Hyun Kim,
Sukwoo Choi,
Hyun Taek Kim,
Chang-Joong Lee,
Kyungjin Kim
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ABSTRACT: Stress in adulthood can have a profound effect on physiology and behavior, but the extent to which prolonged maternal stress affects the brain function of offspring when they are adult remains primarily unknown. In the present work, chronic immobilization stress to pregnant mice affected fetal growth and development. When pups born from stressed mice were reared to adulthood in an environment identical to that of nonstressed controls, several physiological parameters were essentially unaltered. However, spatial learning and memory was significantly impaired in the maternally stressed offspring in adulthood. Furthermore, electrophysiological examination revealed a significant reduction in NMDA receptor-mediated long-term potentiation in the CA1 area of hippocampal slices. Subsequent biochemical analysis demonstrated a substantial decrease in NR1 and NR2B subunits of the NMDA receptor in synapses of the hippocampus, and the interaction between these two subunits appeared to be reduced. These results suggest that prolonged maternal stress leads to long-lasting malfunction of the hippocampus, which extends to and is manifested in adulthood.
Journal of Neuroscience 04/2006; 26(12):3309-18. · 7.11 Impact Factor
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ABSTRACT: To determine the activity and the toxicity associated with a low dose regimen of leucovorin (LV) plus 5-fluorouracil (5-FU) combined with oxaliplatin every two weeks (modified FOLFOX 4) as a salvage therapy for advanced gastric cancer patients.
Between December 2003 and December 2004, 33 patients were enrolled in this study. The patients were treated with oxaliplatin 85 mg/m(2) as a 2-hour infusion on the first day plus LV 20 mg/m(2) over 10 minutes. Subsequently, the patients were given a 5-FU bolus 400 mg/m(2) followed by a 22-hour continuous infusion of 600 mg/m(2) on days 1 approximately 2. The treatment was repeated at 2 week intervals.
The median age of the patients was 50 years (range: 31 approximately 74), 82% (27/33) had the Eastern Cooperative Oncology Group performance status was 0 and 1. Of the 30 patients who could be evaluated for their tumor response, 8 achieved a partial response, with an overall response rate of 26.7% (95% confidence interval (CI): 20.5 approximately 32.7%). Fifteen patients (50%) showed stable disease and 7 patients (23.3%) progressed during the course of treatment. The median time from the start of chemotherapy to progression was 3.5 months (95% CI: 2.6 approximately 4.4 months) and the median overall survival time was 7.9 months (95% CI: 5.9 approximately 9.9 months). The major grade 3/4 hematological toxicity encountered included neutropenia (45.4%) and thrombocytopenia (3.0%). Neutropenic fever occurred during only 2 of the 178 cycles. The most common non-hematological toxicity encountered was grade 1/2 nausea/vomiting, which occurred in 18.2% of patients, diarrhea in 12.1% and neuropathy in 15.2%. There were no treatment related deaths.
The modified FOLFOX 4 regimen appears to be a safe and effective salvage therapy for advanced gastric cancer patients.
Cancer Research and Treatment 10/2005; 37(5):279-83.
