Synthesis of a high-performance citric acid-based polyester elastomer by a hot-pressing technique

Chon, Y.J.,Koo, J.M.,Park, Y.J.,Hwang, S.Y.,Jung, Y.M.,Im, S.S. IPC Science and Technology Press 2017 Polymer Vol.125 No.-

The high-performance bio-based elastomer, poly (1, 4-cyclohexanedimethanol succinate-co-citrate) (PCSC), was successfully synthesized through the combination of melt polymerization and hot pressing. Owing to the structural characteristics of citric acid (CA), an effective process of thermal- and pressure-integrated crosslinking was possible, revealing CA to be a progressive tetra-functional monomer. In the composition of PCSC, there can be four types of ester bonds amongst monomers, of which CA was used in three. Specifically, the stepwise hot-pressing method allowed β-carboxylic acid and hydroxyl group of CA to remain within the synthesized elastomer to enhance its crosslinking density via esterification. As a result, the synthesized PCSC possessed a wide range of mechanical properties along with good thermal resistance. The resulting characteristics were demonstrated by fourier-transform infrared spectroscopy (FT-IR), two-dimensional correlation spectroscopy (2D-COS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile and swelling tests. PCSC is a sustainable and versatile material that can be utilized in the field of engineering.

<i>In vivo</i> stem cell tracking with imageable nanoparticles that bind bioorthogonal chemical receptors on the stem cell surface

Lee, Sangmin,Yoon, Hwa In,Na, Jin Hee,Jeon, Sangmin,Lim, Seungho,Koo, Heebeom,Han, Sang-Soo,Kang, Sun-Woong,Park, Soon-Jung,Moon, Sung-Hwan,Park, Jae Hyung,Cho, Yong Woo,Kim, Byung-Soo,Kim, Sang Kyoon IPC Science and Technology Press 2017 Biomaterials Vol.139 No.-

<P><B>Abstract</B></P> <P>It is urgently necessary to develop reliable non-invasive stem cell imaging technology for tracking the <I>in vivo</I> fate of transplanted stem cells in living subjects. Herein, we developed a simple and well controlled stem cell imaging method through a combination of metabolic glycoengineering and bioorthogonal copper-free click chemistry. Firstly, the exogenous chemical receptors containing azide (-N<SUB>3</SUB>) groups were generated on the surfaces of stem cells through metabolic glycoengineering using metabolic precursor, tetra-acetylated <I>N</I>-azidoacetyl-<SMALL>D</SMALL>-mannosamine(Ac<SUB>4</SUB>ManNAz). Next, bicyclo[6.1.0]nonyne-modified glycol chitosan nanoparticles (BCN-CNPs) were prepared as imageable nanoparticles to deliver different imaging agents. Cy5.5, iron oxide nanoparticles and gold nanoparticles were conjugated or encapsulated to BCN-CNPs for optical, MR and CT imaging, respectively. These imageable nanoparticles bound chemical receptors on the Ac<SUB>4</SUB>ManNAz-treated stem cell surface specifically via bioorthogonal copper-free click chemistry. Then they were rapidly taken up by the cell membrane turn-over mechanism resulting in higher endocytic capacity compared non-specific uptake of nanoparticles. During <I>in vivo</I> animal test, BCN-CNP-Cy5.5-labeled stem cells could be continuously tracked by non-invasive optical imaging over 15 days. Furthermore, BCN-CNP-IRON- and BCN-CNP-GOLD-labeled stem cells could be efficiently visualized using <I>in vivo</I> MR and CT imaging demonstrating utility of our stem cell labeling method using chemical receptors. These results conclude that our method based on metabolic glycoengineering and bioorthogonal copper-free click chemistry can stably label stem cells with diverse imageable nanoparticles representing great potential as new stem cell imaging technology.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Assessment of long-term cryopreservation for production of hCTLA4Ig in transgenic rice cell suspension cultures

Kwon, J.Y.,Jeong, S.H.,Choi, J.W.,Pak, Y.Y.,Kim, D.I. IPC Science and Technology Press ; Elsevier Scienc 2013 Enzyme and microbial technology Vol.53 No.3

For the commercialization of plant-made pharmaceuticals (PMPs) using transgenic plant cell cultures, the establishment of a cell-banking system has been known to be an essential process. Plant cells are traditionally maintained by repeated subcultures. However, this method has several problems including genetic instability of transformed cell lines, time- and cost-consuming. In this study, long-term cryopreserved rice suspension cells were firstly investigated for the production of human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig). The cryopreserved cells for 5 years were regrowed to callus successfully and then suspended into the liquid medium. Consequently, the maximum cell mass and the hCTLA4Ig production were similar levels compared to those of the non-cryopreserved cells (control) even though hCTLA4Ig productivity was 1.7-fold higher than that of control. To further assess the level of improvements in hCTLA4Ig productivity in cryopreserved cells, hCTLA4Ig production profiles were statistically assessed between data of the cryopreserved cells for 5 years and annual data of non-cryopreserved cells maintained by subculture for 5 years. These results also indicate that hCTLA4Ig productivity in cryopreserved cells for 5 years was significantly increased (p-value: <0.001, 95% confidence interval) and it could be related to cell lysis resulting in release of hCTLA4Ig which was confirmed by the measurement of electrolyte leakage. In conclusion, we show that the long-term cryopreservation of transgenic rice cells was possible to support stable cell lines for the production of PMPs.

Enhanced optical properties and thermal stability of optically clear adhesives

Lee, S.W.,Park, J.W.,Park, C.H.,Kim, H.J. IPC Science and Technology Press ; Elseiver Scienc 2014 International journal of adhesion & adhesives Vol.50 No.-

To improve the optical properties of acrylic pressure-sensitive adhesives (PSAs) for liquid crystal displays (LCDs), hafnium carboxyethyl acrylate (HCA) was introduced as high refractive index material. Also, UV-curing was used to realize rapid crosslinking so as to enhance the degree of thermal stability. A prism coupler, a UV-visible spectrometer and a thermogravimetric analyzer were employed to assess the optical properties and thermal stability. The results show that the refractive index of the acrylic PSAs with HCA increases suitably compared to that of binder acrylic PSAs in the visible wavelength. Also, a substantial effect is shown on the thermal stability in that hafnium carboxyethyl acrylates are crosslinked due to the presence of tetra-functional acrylic groups caused by the rapid UV-curing.

An evaluation of the fatigue crack propagation rate for powder metallurgical nickel-based superalloys using the DCPD method at elevated temperatures

Na, S.,Yoon, D.,Kim, J.,Kim, H.,Kim, D. IPC Science and Technology Press ; Elsevier Scienc 2017 International journal of fatigue Vol.101 No.1

<P>This study investigates the fatigue-crack propagation behavior of a powder metallurgical nickel-based superalloy, used in aircraft turbine disks. Taking into consideration the various operating conditions, the fatigue-crack propagation tests were conducted at various temperatures and stress ratios. These tests were performed with using the direct current potential drop method suggested by ASTM E647. Using Paris' law, the fatigue life can be predicted and the fatigue strengths can be calculated for developing a damage-tolerant design to predict the defects at elevated temperatures. The fatigue crack propagation rates at elevated temperatures are higher than that at room temperature. In addition, scanning electron microscope (SEM) observations of the fracture surface at different temperatures were examined and compared. At elevated temperatures, intergranular fractures are appeared with the oxidation. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Preparation of glutaraldehyde-treated lipase-inorganic hybrid nanoflowers and their catalytic performance as immobilized enzymes

Lee, H.R.,Chung, M.,Kim, M.I.,Ha, S.H. IPC Science and Technology Press ; Elsevier Scienc 2017 Enzyme and microbial technology Vol.105 No.-

<P>The use of protein-inorganic hybrid nanoflowers for the immobilization of enzymes has received a significant degree of attention owing to their capability to retain high enzymatic activity and stability. However, the relative lack of reusability due to the weakness of the flower-like structure has limited their practical applications. Herein, we have developed a simple but efficient method to synthesize highly robust enzyme-inorganic hybrid nanoflowers,which relies on further crosslinking of the enzyme molecules entrapped in the hybrid nanoflowers by treatment with glutaraldehyde (GA). By employing lipase from Candida rugosa as a model enzyme with copper phosphate during 3 days incubation followed by the additional GA treatment for only 1 h, we could successfully synthesize GA-treated lipase nanoflowers having similar flower-like morphology and hydrolytic activity (ca. 95% compared with the free lipase) as conventionally synthesized lipase nanoflowers without GA treatment. Importantly, the conventional lipase nanoflowers seemed not to be reusable because they lost most of their activity (90%) after recycling 4 times, whereas GA-treated lipase nanoflowers exhibited higher retention of their initial activity (over 70%) after 4 reuses, which was also accompanied by an efficient maintenance of their flower-like morphology. Based on our results, we expect that this simple GA-mediated strategy to synthesize enzyme-inorganic hybrid nanoflowers can be readily extended to other enzymes for various biotechnological applications.</P>

UV- and thermal-curing behaviors of dual-curable adhesives based on epoxy acrylate oligomers

Park, Y.-J.,Lim, D.-H.,Kim, H.-J.,Park, D.-S.,Sung, I.-K. IPC Science and Technology Press ; Elseiver Scienc 2009 International journal of adhesion & adhesives Vol.29 No.7

Dual-curable adhesives were prepared using various epoxy acrylate oligomers, a reactive diluent, photoinitiators, a thermal-curing agent and a filler. The UV- and thermal-curing behaviors of the dual-curable adhesives were investigated using photo-differential scanning calorimetry (photo-DSC), Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, and the determination of the gel fraction, pendulum hardness and adhesion strength. The reaction rate and extent of UV curing were found to be strongly dependent on the concentration of C?C bonds in the epoxy acrylate oligomers. The FTIR-ATR absorption peak areas representing the relative concentration of C?C bonds in the epoxy acrylate oligomers and trifunctional monomer decreased with increase in UV dose because of photopolymerization. When the dual-curable adhesives were irradiated with UV light, the gel fraction increased with increase in C?C bond contents in the epoxy acrylate oligomers. Also, after thermal curing, the gel fraction was highly enhanced due to the cross-linking reaction of the unreacted glycidyl groups in epoxy acrylate oligomers induced by the thermal-curing agent. This cross-linked structure of the dual-curable adhesives affects the pendulum hardness and adhesion strength.

Effect of laminating parameters on the adhesion property of flexible copper clad laminate with adhesive layer

Noh, B.-I.,Yoon, J.W.,Jung, S.B. IPC Science and Technology Press ; Elseiver Scienc 2010 International journal of adhesion and adhesives Vol.30 No.1

In this study, the effect of two laminating parameters, laminating pressure and holding time, on the adhesion strength of flexible copper clad laminate (FCCL) with an epoxy-type adhesive layer was evaluated. The changes in the adhesion property, fracture surface, morphology, and chemical bonding state were characterized by 90<SUP>o</SUP> peel test, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that the adhesion strength of the FCCL was decreased as the laminating pressure was increased beyond the suitable level. Laminating pressure exerted the greatest influence over the FCCL adhesion strength. On the other hand, the holding time did not significantly affect the peel strength of the FCCL. The fracture of FCCL occurred at the interface between the rolled Cu and the adhesive layer. In addition, the FCCL with high adhesion strength was stable with the variation of adhesion strength after temperature and humidity test.

Development of Escherichia coli MG1655 strains to produce long chain fatty acids by engineering fatty acid synthesis (FAS) metabolism

Jeon, E.,Lee, S.,Won, J.I.,Han, S.O.,Kim, J.,Lee, J. IPC Science and Technology Press ; Elsevier Scienc 2011 Enzyme and microbial technology Vol.49 No.1

The goal of this research was to develop recombinant Escherichia coli to improve fatty acid synthesis (FAS). Genes encoding acetyl-CoA carboxylase (accA, accB, accC), malonyl-CoA-[acyl-carrier-protein] transacylase (fabD), and acyl-acyl carrier protein thioesterase (EC 3.1.2.14 gene), which are all enzymes that catalyze key steps in the synthesis of fatty acids, were cloned and over-expressed in E. coli MG1655. The acetyl-CoA carboxylase (ACC) enzyme catalyzes the addition of CO<SUB>2</SUB> to acetyl-CoA to generate malonyl-CoA. The enzyme encoded by the fabD gene converts malonyl-CoA to malonyl-[acp], and the EC 3.1.2.14 gene converts fatty acyl-ACP chains to long chain fatty acids. All the genes except for the EC 3.1.2.14 gene were homologous to E. coli genes and were used to improve the enzymatic activities to over-express components of the FAS pathway through metabolic engineering. All recombinant E. coli MG1655 strains containing various gene combinations were developed using the pTrc99A expression vector. To observe changes in metabolism, the in vitro metabolites and fatty acids produced by the recombinants were analyzed. The fatty acids (C16) from recombinant strains were produced 1.23-2.41 times higher than that from the wild type.

Extracellular synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 and their biological applications

Singh, P.,Singh, H.,Kim, Y.J.,Mathiyalagan, R.,Wang, C.,Yang, D.C. IPC Science and Technology Press ; Elsevier Scienc 2016 Enzyme and microbial technology Vol.86 No.-

<P>The present-study highlights the microbial synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 strain, in an efficient way. The synthesized nanoparticles were characterized by ultraviolet visible spectrophotometry, which displayed maximum absorbance at 424 nm and 531 nm for silver and gold nanoparticles, respectively. The spherical shape of nanoparticles was characterized by field emission transmission electron microscopy. The energy dispersive X-ray spectroscopy and elemental mapping were displayed the purity and maximum elemental distribution of silver and gold elements in the respective nanoproducts. The X-ray diffraction spectroscopy results demonstrate the crystalline nature of synthesized nanoparticles. The particle size analysis demonstrate the nanoparticles distribution with respect to intensity, volume and number of nanoparticles. For biological applications, the silver nanoparticles have been explored in terms of MIC and MBC against pathogenic microorganisms such as Vibrio parahaemolyticus, Escherichia coli, Salmonella enterica, Bacillus anthracis, Bacillus cereus and Staphylococcus aureus. Moreover, the silver nanoparticles in combination with commercial antibiotics, such as vancomycin, rifampicin, oleandomycin, penicillin G, novobiocin, and lincomycin have been explored for the enhancement of antibacterial activity and the obtained results showed that 3 mu g concentration of silver nanoparticles sufficiently enhance the antimicrobial efficacy of commercial antibiotics against pathogenic microorganism. Furthermore, the silver nanoparticles potential has been reconnoitered for the biofilm inhibition by S. aureus, Pseudomonas aeruginosa and E. coli and the results revealed sufficient activity at 6 mu g concentration. In addition, gold nanoparticles have been applied for catalytic activity, for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride and positive results were attained. (C) 2016 Elsevier Inc. All rights reserved.</P>