Jong-Kil Kim

Expert drawbead models for finite element analysis of sheet metal forming processes

The expert drawbead model which computes the drawing characteristics of the drawbead used in a finite element analysis of sheet metal forming processes is developed. The mathematical models of the basic drawbeads such as the circular drawbead, stepped drawbead, and squared drawbead, whose dimensions and processes are various, are first derived using the bending theory, belt-pulley equation, and Coulomb friction law. Next, the experiments for finding the drawing characteristics of the drawbead are performed. Based on the mathematical model, the expert model of the basic drawbead is then developed employing a linear multiple regression method by which the difference in drawing characteristics between the drawing test and the mathematical model is minimized. For the expert models of combined drawbeads such as the double circular drawbead, double stepped drawbead, circular-and-stepped drawbead, etc., those of the basic drawbeads are summed. Finally, to verify the expert models developed, the drawbead restraining force and bead-exit pre-strain calculated by the expert models of the double circular drawbead and circular-and-stepped drawbead are compared with those obtained from the experiments. The predictions by expert models agree well with the measurements by the experiments.

Effective Gene Delivery into Human Stem Cells with a Cell‐Targeting Peptide‐Modified Bioreducible Polymer

Stem cells are poorly permissive to non-viral gene transfection reagents. In this study, we explored the possibility of improving gene delivery into human embryonic (hESC) and mesenchymal (hMSC) stem cells by synergizing the activity of a cell-binding ligand with a polymer that releases nucleic acids in a cytoplasm-responsive manner. A 29 amino acid long peptide, RVG, targeting the nicotinic acetylcholine receptor (nAchR) was identified to bind both hMSC and H9-derived hESC. Conjugating RVG to a redox-sensitive biodegradable dendrimer-type arginine-grafted polymer (PAM-ABP) enabled nanoparticle formation with plasmid DNA without altering the environment-sensitive DNA release property and favorable toxicity profile of the parent polymer. Importantly, RVG-PAM-ABP quantitatively enhanced transfection into both hMSC and hESC compared to commercial transfection reagents like Lipofectamine 2000 and Fugene. ∼60% and 50% of hMSC and hESC were respectively transfected, and at increased levels on a per cell basis, without affecting pluripotency marker expression. RVG-PAM-ABP is thus a novel bioreducible, biocompatible, non-toxic, synthetic gene delivery system for nAchR-expressing stem cells. Our data also demonstrates that a cell-binding ligand like RVG can cooperate with a gene delivery system like PAM-ABP to enable transfection of poorly-permissive cells.

Recovery of high surface area mesoporous silica from waste hexafluorosilicic acid (H2SiF6) of fertilizer industry

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H(2)SiF(6)) and 100ml, 0.297 M Na(2)CO(3) to generate the alkaline aqueous slurry. Silica was separated from the slurry by filtration and the sodium fluoride was extracted from the aqueous solution by evaporation method. The obtained mesoporous silica was characterized by N(2) absorption/desorption (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results confirm that the separation of silica and NaF was successful and the final products have high purity. The silica product was found to have an average pore diameter of 4.14 nm and a high surface area (up to 800 m(2)/g). The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries.

Application of an expert drawbead model to the finite element simulation of sheet forming processes

Abstract An expert model developed for the simple description of the drawbead in the numerical simulation of stamping processes is introduced. The drawbead restraining force and bead-exit thinning that the expert drawbead model calculates employing the drawbead dimensions and forming variables are used as a boundary condition of the node nearest to the drawbead position. In order to show the efficiency and accuracy of the expert drawbead model, the numerical simulation of auto-body panel stamping is performed. The new numerical model provides an accurate solution and stable convergence. It also has merit in not requiring excessive computation time.

Silencing CCR2 in Macrophages Alleviates Adipose Tissue Inflammation and the Associated Metabolic Syndrome in Dietary Obese Mice

Adipose tissue macrophage (ATM)-mediated inflammation is a key feature contributing to the adverse metabolic outcomes of dietary obesity. Recruitment of macrophages to obese adipose tissues (AT) can occur through the engagement of CCR2, the receptor for MCP-1 (monocyte chemoattractant protein-1), which is expressed on peripheral monocytes/macrophages. Here, we show that i.p. administration of a rabies virus glycoprotein-derived acetylcholine receptor-binding peptide effectively delivers complexed siRNA into peritoneal macrophages and ATMs in a mouse model of high-fat diet-induced obesity. Treatment with siRNA against CCR2 inhibited macrophage infiltration and accumulation in AT and, therefore, proinflammatory cytokines produced by macrophages. Consequently, the treatment significantly improved glucose tolerance and insulin sensitivity profiles, and also alleviated the associated symptoms of hepatic steatosis and reduced hepatic triglyceride production. These results demonstrate that disruption of macrophage chemotaxis to the AT through cell-targeted gene knockdown strategies can provide a therapeutic intervention for obesity-related metabolic diseases. The study also highlights a siRNA delivery approach for targeting specific monocyte subsets that contribute to obesity-associated inflammation without affecting the function of other tissue-resident macrophages that are essential for host homeostasis and survival.

Synthesis of silica support for biocatalyst immobilization

Abstract Bioconversion processes utilizing an immobilized biocatalyst (enzyme) are widely used to synthesize various kinds of medicines. The support for biocatalyst, such as silica, plays an important role in the overall yield of the bioconversion reaction because they determine the loading capacity of the active biocatalyst. In this study, nanoporous silicas suitable for the support, were synthesized via a salt route and the pore morphology in silicas were characterized. Then, D-amino acid oxydase, the enzyme for the conversion reaction to synthesize an antibiotic, was immobilized in the above silicas and the activity of immobilized enzyme was investigated in relation to the pore morphology.

Two-step rapid synthesis of mesoporous silica for green tire

We report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste material (hexafluorosilicic acid, H2SiF6) of phosphate fertilizer industry and sodium silicate (Na2O·SiO2). The reaction was performed in a newly innovated manufacturing apparatus. This apparatus produces mesoporous silica with uniform properties through controlled mixing of source materials at predetermined equivalent ratio. The precursors are rapidly mixed within the nozzles to enable uniform control of physical properties of the final product. The obtained mesoporous silica was characterized using N2 physisorption studies, scanning electron microscope (SEM), and EDS. The final product was found to have superior properties that are suitable for green tire (environmentally friendly tire) as inorganic filler. The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries. A project on innovative industrial application of our products for the tire industry is in progress.

Trileucine residues in a ligand-CPP-based siRNA delivery platform improve endosomal escape of siRNA

Abstract siRNA entrapment within endosomes is a significant problem encountered with siRNA delivery platforms that co-opt receptor-mediated entry pathways. Attachment of a cell-penetrating peptide (CPP), such as nona-arginine (9R) to a cell receptor-binding ligand like the Rabies virus glycoprotein, RVG, allows effective siRNA delivery to the cytoplasm by non-endocytic pathways, but a significant amount of siRNA complexes also enters the cell by ligand-induced receptor endocytosis and remain localized in endosomes. Here, we report that the incorporation of trileucine (3 Leu) residues as an endo-osmolytic moiety in the peptide improves endosomal escape and intracellular delivery of siRNA. The trileucine motif did not affect early non-endosomal mechanism of cytoplasmic siRNA delivery but enhanced target gene silencing by >20% only beyond 24 h of transfection when siRNA delivery is mostly through the endocytic route and siRNA trapped in the endosomes at later stages were subject to release into cytoplasm. The mechanism may involve endosomal membrane disruption as trileucine residues lysed RBCs selectively under endosomal pH conditions. Interestingly <3 Leu or >3 Leu residues were not as effective, suggesting that 3 Leu residues are useful for enhancing cytoplasmic delivery of siRNA routed through endosomes.

Proliferation of prostate epithelia induced by IL-6 from stroma reacted with Trichomonas vaginalis.

Benign prostatic hyperplasia (BPH) is characterized by the proliferation of stromal and epithelial cell types in the prostate, and interactions between the two types of cells. We demonstrated previously that proliferation of prostate stromal cells was induced by BPH epithelial cells in response to Trichomonas vaginalis (Tv) infection via crosstalk with mast cells. In this study, we investigated whether IL‐6 released by the proliferating stromal cells in turn induce the BPH epithelial cells to multiply. When culture supernatants of the proliferating prostate stromal cells were added to BPH epithelial cells, the latter multiplied, and expression of cyclin D1, FGF2 and Bcl‐2 increased. Blocking the IL‐6 signalling pathway with anti‐IL‐6R antibody or JAK1/2 inhibitor inhibited the proliferation of the BPH epithelial cells and reduced the expression of IL‐6, IL‐6R and STAT3. Also, epithelial‐mesenchymal transition was detected in the proliferating BPH epithelial cells. In conclusion, IL‐6 released from proliferating prostate stromal cells induced by BPH epithelial cells infected with Tv in turn induces multiplication of the BPH epithelial cells. This result provides first evidence that the inflammatory microenvironment of prostate stromal cells resulting from Tv infection induces the proliferation of prostate epithelial cells by stromal‐epithelial interaction.