Transesterification reaction of the BaSO4‐filled PBT/poly(ethylene terephthalate) blend

For the poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) blend system, the addition of a barium sulfate (BaSO₄) particle, the surface of which was modified with a titanate coupling agent, suppressed the transesterification reaction. The polyester chain ends, considered one of the main sites of transesterification reactions, were blocked through a chemical reaction with the surface hydroxyl groups of the BaSO₄ particle; a block copolymer‐like architecture was obtained with a BaSO₄ linkage. The formation of the block copolymer‐like structure for the polyesters stuck to the BaSO₄ particle facilitated crystallization by providing a crystallization nucleus without a significant transesterification reaction, resulting in higher mechanical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2589–2597, 2001     

Specific interaction governing the melt intercalation of clay with poly(styrene‐co‐acrylonitrile) copolymers

In the melt intercalation of cation‐exchange clay, mixtures of montmorillonite and poly(styrene‐co‐acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amount of SAN penetrating the gallery of the layered structure of the clay and the corresponding increase in the gallery height occurred at a much higher rate because of the attractive specific interaction between acrylonitrile groups and polar groups on the clay surface. However, there was a limit to the increase in the gallery height, and the tendency for the gallery height to increase with the acrylonitrile group content disappeared when the acrylonitrile content was greater than 30 wt %, implying that excessive attractive interaction on the clay surfaces and polymer molecules glued the two adjacent silicate layers together; consequently, the increase in the gallery height could not be accomplished. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2430–2435, 2001     

Multifunctional Fe3O4/TaO(x) core/shell nanoparticles for simultaneous magnetic resonance imaging and X-ray computed tomography

Multimodal imaging is highly desirable for accurate diagnosis because it can provide complementary information from each imaging modality. In this study, a sol-gel reaction of tantalum(V) ethoxide in a microemulsion containing Fe(3)O(4) nanoparticles (NPs) was used to synthesize multifunctional Fe(3)O(4)/TaO(x) core/shell NPs, which were biocompatible and exhibited a prolonged circulation time. When the NPs were intravenously injected, the tumor-associated vessel was observed using computed tomography (CT), and magnetic resonance imaging (MRI) revealed the high and low vascular regions of the tumor.     

Evaluation of Thermal and Analytical Properties of Two Liquid Crystals in Capillary GC

Comparative gas chromatographic applications of two new liquid crystals were investigated. The characterization of the two mesogenic compounds was performed with ¹H NMR and mass spectrometry. The thermal properties were established by differential scanning calorimetry. The optical characterization of the liquid crystal was made by using polarizing optical microscopy. The chromatographic separation abilities of the mesogenic compounds were studied using fused silica capillary columns. Interesting analytical performances were obtained notably in the separation of volatile aroma compounds and derivatives phenols.     

Isoflavone-deprived soy peptide suppresses mammary tumorigenesis by inducing apoptosis

During carcinogenesis, NF-κB mediates processes associated with deregulation of the normal control of proliferation, angiogenesis, and metastasis. Thus, suppression of NF-κB has been linked with chemoprevention of cancer. Accumulating findings reveal that heat shock protein 90 (HSP90) is a molecular chaperone and a component of the IκB kinase (IKK) complex that plays a central role in NF-κB activation. HSP90 also stabilizes key proteins involved in cell cycle control and apoptosis signaling. We have determined whether the exogenous administration of isoflavone-deprived soy peptide prevents 7,12-dimethylbenz[α]anthracene (DMBA)-induced rat mammary tumorigenesis and investigated the mechanism of action. Dietary administration of soy peptide (3.3 g/rat/day) significantly reduced the incidence of ductal carcinomas (50%), the number of tumors per multiple tumor-bearing rats (49%; P < 0.05), and extended the latency period of tumor development (8.07 ± 0.92 weeks) compared to control diet animals (10.80 ± 1.30; P < 0.05). Our results have further demonstrated that soy peptide (1) dramatically inhibits the expression of HSP90, thereby suppressing signaling pathway leading to NF-κB activation; (2) induces expression of p21, p53, and caspase-3 proteins; and (3) inhibits expression of VEGF. In agreement with our in vivo data, soy peptide treatment inhibited the growth of human breast MCF-7 tumor cells in a dose-dependent manner and induced apoptosis. Taken together, our in vivo and in vitro results suggest chemopreventive and tumor suppressive functions of isoflavone-deprived soy peptide by inducing growth arrest and apoptosis.     

Effect of the chain length on the thermal and analytical properties of laterally biforked nematogens

Three laterally substituted liquid crystals were synthesized in order to investigate the effect of a lateral biforked chain on the thermal and analytical properties. The mesogenic molecules have the same core containing four aromatic rings connected by two ester and one diazo linkages, they differ by the length of one chain within the lateral biforked substituent. The phase transition temperatures were obtained by polarized light microscopy and differential scanning calorimetry (DSC). The clearing temperature and the nematic range decrease with increasing length of the lateral biforked chain. The stationary phases derived from these nematogens provide excellent resolution of various classes of compounds, including aromatic hydrocarbons (AH), substituted benzenes, polycyclic aromatic hydrocarbons (PAH), phenols and volatile organic compounds (VOC) present in the essential oils. The selectivities of the stationary phases were found to decrease according to the length of the side chain.     

Control of Osteogenic Differentiation and Mineralization of Human Mesenchymal Stem Cells on Composite Nanofibers Containing Poly[lactic‐co‐(glycolic acid)] and Hydroxyapatite

We fabricated composite fibrous scaffolds from blends of poly(lactide‐co‐glycolide) (PLGA) and nano‐sized hydroxyapatite (HA) via electrospinning. SEM‐EDX and AFM analysis demonstrated that HA was homogeneously dispersed in the nanofibers, and the roughness increased along with the amount of incorporated HA. When hMSCs were cultured on these PLGA/HA composite nanofibers, we found that incorporation of HA on the nanofibers did not affect cell viability whereas increased ALP activity and expression of osteogenic genes as well as the calcium mineralization of hMSCs. Our results indicate that the composite nanofibers can be offered as a potential bone regenerative biomaterial for stem cell based therapies.