Effects of bioactive ceramics on the pathogenesis of rat vascular smooth muscle cells treated with phorbol 12-myristate 13-acetate

Vascular smooth muscle cells (VSMCs) play a pivotal role in vascular injury through proliferation and migration. Pro-inflammatory cytokines and cyclooxygenase (COX)-2 and nitric oxide synthase (NOS) are highly associated with the pathogenesis of VSMCs. We investigated the effect of bioactive ceramics on the expression of inflammatory cytokines, COX-2, and inducible NOS (iNOS) induced by phorbol 12-myristate 13-acetate (PMA) in rat VSMCs. The ceramics inhibited mRNA expression of IL-1β, TNF-α, IL-6, COX-2, and iNOS. Prostaglandin release was also diminished by the ceramics. The bioactive ceramics effect on cytokines, COX-2, and iNOS expression was achieved by inhibition of NF-κB activity. Interestingly, the ceramics-induced up-regulation of expression of endothelial NOS resulted in an increase of nitric oxide production. Thus, bioactive ceramics may have dual effects on the pathogenesis of VSMCs by regulation of NF-κB activity and NO production.     

High-temperature tensile-hold crack-growth behavior of HASTELLOY<Superscript>®</Superscript> X alloy compared to HAYNES<Superscript>®</Superscript> 188 and HAYNES<Superscript>®</Superscript> 230<Superscript>®</Superscript> alloys

The creep–fatigue crack-growth tests of HASTELLOY^® X alloy were carried out at the temperatures of 649°C, 816°C, and 927°C in laboratory air. The experiments were conducted under a constant stress-intensity-factor-range (ΔK) control mode with a R-ratio of 0.05. In the constant ΔK tests, a ΔK of 27.5 MPa\(\sqrt{\mathrm{m}}\) and a triangular waveform with a frequency of 0.333 Hz were used. Various tensile hold times at the maximum load were imposed to study fatigue and creep–fatigue interactions. Crack lengths were measured by a direct current potential drop method. In this paper, effects of hold time and temperature on the crack-growth rates are discussed. Furthermore, the crack-growth rates of the HASTELLOY^® X alloy are compared to those of the HAYNES^® 188 and HAYNES^® 230^® superalloys.     

Development of an Electroosmotic Pump Using Nanosilica Particle Packed Capillary

High-pressure electroosmotic pumps (EOPs) operate on the principle that electroosmotic flow (EOF) can be generated through a packed-bed capillary by applying an electric field through it. In this paper, a novel packed-bed EOP design using nanosilica particles is described. The packed-bed capillary was fabricated using a capillary of 5 cm x 530 mum i.d. close packed with silica particles having an average particle size of 20-30 nm. The flow rates, pressures and pressure/flow rate (P-Q)characteristics, electric properties of the pump and the influence of phosphate buffer concentration on the pump were carefully studied. By increasing the pressure, decreasing the applied voltage, and the electric current, the thermodynamic efficiency was about 1%-2% for inorganic buffers and 3%-5% for organic solvents or their mixture without ions.     

Biological imaging of HEK293 cells expressing PLCgamma1 using surface-enhanced Raman microscopy

Surface-enhanced Raman scattering (SERS) imaging has been used for the targeting and imaging of specific cancer markers in live cells. For this purpose, Au/Ag core-shell nanoparticles, conjugated with monoclonal antibodies, were prepared. The procedures to label live cells with those bimetallic nanoprobes have been developed and used for highly sensitive SERS imaging of live cells. In the present study, live HEK293 cells expressing PLCgamma1 have been used as the optical imaging target. Our results demonstrate the potential feasibility of SERS imaging technology for the highly sensitive imaging of cancer biomarkers in live cells.     

A two-photon fluorescent probe for lipid raft imaging: C-laurdan

The lipid-rafts hypothesis proposes that naturally occurring lipid aggregates exist in the plane of membrane that are involved in signal transduction, protein sorting, and membrane transport. To understand their roles in cell biology, a direct visualization of such domains in living cells is essential. For this purpose, 6-dodecanoyl-2-(dimethylamino)naphthalene (laurdan), a membrane probe that is sensitive to the polarity of the membrane, has often been used. We have synthesized and characterized 6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (C-laurdan), which has the advantages of greater sensitivity to the membrane polarity, a brighter two-photon fluorescence image, and reflecting the cell environment more accurately than laurdan. Lipid rafts can be visualized by two-photon microscopy by using C-laurdan as a probe. Our results show that the lipid rafts cover 38 % of the cell surface.     

Synthesis and characterization of PS-clay nanocomposite by emulsion polymerization

Summary Polystyrene-Na⁺-montmorillonite(PS-Na⁺-MMT) nanocomposites are prepared by a simple emulsion polymerization. The X-ray diffraction(XRD) and infrared spectroscopy (IR) analysis confirm that polystyrene(PS) macromolecules can be inserted between lamella layers and whose layer separation is consequently higher than in the polymer-free clay. The enhanced thermal properties of composites are measured by differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA) thermogram and indicate that the glass transition and the decomposition onset temperature of obtained nanocomposites are found to be moved to the higher temperature region. The increased Young's modulus of the obtained nanocomposites is ascribed to the intercalation of PS in clay galleries as well as the fine dispersion of clay particles into the polymer matrix. Received: 23 February 1999/Revised version: 26 March 1999/Accepted: 1 April 1999     

Alternating copolymers as compatibilizer for blends of poly(ethylene terephthalate) and polystyrene

Compatibilization of blends of poly(ethylene terephthalate) (PET) and polystyrene with alternating copolymers of maleic anhydride and isobutylene (IM) and its partly phenol substituted product (PIM) has been studied. The characterization techniques applied were dynamic mechanical analysis, differential scanning calorimetry, scanning electron microscopy, and tensile testing. In all compositions studied, morphological observations demonstrated that the addition of approximately 5 wt % of copolymers led to the domain size reduction of dispersants. The PIM copolymer was most effective in reducing the domain size, whereas the IM copolymer was less satisfactory. The blends containing PIM also gave the more enhanced ultimate strength than those of other systems. The noncrystalline PIM copolymers lowered the tensile modulus of the blend as much as 60% even in the polystyrene‐rich region and varied linearly with values of quenched PET modulus throughout the compositions, indicating the formation of homogeneous amorphous phase. Based on the experimental observation that the reduced domain size with PIM copolymer, a compatibilization mechanism of the blend with PIM alternating copolymer is proposed and discussed in terms of the interactions between ester groups of PET and PIM (transesterification), and the possible formation of intermediate π‐complex between the π‐electron deficient aromatic ring of PIM and π‐electron rich aromatic ring of PS. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1998–2007, 2000     

Toughening of epoxy resins with aromatic polyesters

Polyesters, prepared by direct polycondensation from bisphenol A and aliphatic dicarboxylic acids [adipic acid (AD), suberic acid, sebacic acid (SE), and dodecanedioic acid], were used to improve the toughness of the diglycidyl ether of the bisphenol A/diaminodiphenyl methane epoxy system. Polyesters had the number average molecular weight (M_n) ranging from 4300 to 19,200 g/mole. The epoxy systems modified with the AD system (M_n = 6400 g/mole) and the SE system (M_n = 10,200 g/mole) showed phase separated structures with discrete domains of 0.2 μm, but other systems showed smooth fracture surfaces when observed by scanning electron microscopy. The modified epoxy systems except for the AD system and SE system showed two tan δ peaks corresponding to the α and β transitions of the epoxy resin. The modified epoxy systems showed maximum values of K_1c at around 10 wt % of polyester and maximum flexural properties at 5 wt % of polyester. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2464–2473, 2000     

Characterization of epoxy–clay hybrid composite prepared by emulsion polymerization

This article demonstrates the direct intercalation of an epoxy polymer in the interlayer of Na⁺–montmorillonite (MMT) by a step type of polymerization in an aqueous emulsion media. The synthesis and the results of structural and thermal characterizations for this hybrid composite are described. Equimolar quantities of bisphenol A and an epoxy prepolymer (n = 0.2) in an emulsion media were polymerized in the presence of Na⁺–MMT. X-ray diffraction (XRD) data obtained from the acetone-extracted products show that the basal spacing of the MMT is expanded from 0.96 to 1.64 nm. Thermal characterization for the postcured products by TGA and DSC gave evidence of enhanced thermal stabilities. SEM examination of the uncured products revealed that a disordered phase begins to appear with increasing polymer loading. However, the XRD profile supported that an overwhelming fraction of the nanocomposite contains intercalated clay. Also, the possibility of intercalation by the emulsion technique is proposed on the basis of the swelling characteristics of MMT in aqueous media and the sizes of micelles containing a monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1997–2005, 1998     

Comparison of characteristics of SAN–MMT nanocomposites prepared by emulsion and solution polymerization

Nonextractable styrene–acrylonitrile copolymer–montmollironite (SAN–MMT) nanocomposites were prepared by two different intercalation process: (1) a usual one‐step emulsion copolymerization in the presence of the Na⁺–MMT; and (2) a solution copolymerization with MMT modified by dimethyl dihydrogenated tallow ammonium. For comparative purposes, the copolymerization conditions (such as comonomer feed ratio and the polymerization temperature and times) were set up to be the same. The X‐ray diffraction pattern demonstrated that the net increase of basal spacing of the purified emulsion products (0.76 nm) far exceeded that of composite (0.39 nm) prepared by solution method. The average molecular masses recovered from the composite extracts revealed M_w = 53 × 10⁴ for emulsion products, while the composite made by solution yielded M_w = 4.8 × 10⁴ g/mol. Likewise, the hybrid from the emulsion polymerization exhibited higher stress at maximum load over the solution products. The dispersibility of MMT particles in the polymer matrix was investigated by using optical microscopy (OM) and scanning electron microscopy (SEM) for those unextracted samples. It was found that almost complete hybrids were obtained when the styrene (ST)–acrylonitryl (AN) comonomer was emulsion polymerized in the presence of Na⁺–MMT, yielding both better miscibility and intercalation capability. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2811–2819, 1999