Two‐dimensional electrolyte nature of exfoliated montmorillonite nanoplatelets fabricated by soap‐free emulsion polymerization and their affinity for cations

Montmorillonite (MMT) nanoplatelets, fabricated by the exfoliation of MMT during participating in the soap‐free emulsion polymerization of methyl methacrylate, were well‐dispersed in water and performed like a two‐dimensional electrolyte. Their ionic conductivity roughly follows the Manning's limiting law for the conduction of a polyelectrolyte. The dissociated MMT nanoplatelets that carry negative charges in water were able to rapidly adsorb cations, such as tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy)) and methylene blue (MB⁺), and recover into a smectic configuration floating as a separating phase. By using the Langmuir equation, we were able to estimate the occupied surface areas of MMT nanoplatelets by each Ru(bpy) and MB⁺ cations as 4.708 and 1.806 nm²/ion, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improved mechanical properties and special reinforcement mechanism of natural rubber reinforced by in situ polymerization of zinc dimethacrylate

The peroxide‐cured natural rubber (NR) was reinforced by in situ polymerization of zinc dimethacrylate (ZDMA). The experimental results showed NR could be greatly reinforced by ZDMA. The tensile strength and the hardness of NR/ZDMA composites increased with the content of ZDMA. The reinforcement mechanism was studied further. Both high crosslinking density provided by ionic crosslinking and strain‐induced crystallization improved the mechanical properties. The crosslinking density was determined by an equilibrium swelling method and the crystallization index was measured by Wide‐angle X‐ray diffraction (WXRD). When the amount of ZDMA was high, the ability of strain‐induced crystallization decreased, due to the strong interactions between the rubber phase and the hard poly‐ZDMA (PZDMA) nanodispersions. At the moment, the increasing ionic crosslinking density made up for the effect of the drop of the strain‐induced crystallization, and played a more important role in the reinforcement. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Intravenous bufadienolides‐loaded lipid microspheres for improving chemical stability

This study focused on the degradation kinetics of bufalin (B), cinobufagin (C), and resibufogenin (R) in bufadienolides‐loaded lipid microsphere (BU‐LM) and bufadienolides‐loaded aqueous solution (BU‐S). The chemical stability of bufadienolides both in BU‐LM and BU‐S at different pH values and temperatures was monitored by HPLC. Photon correlation spectroscopy and electrophoretic light scattering technology were used to evaluate the physical characteristic of BU‐LM. Under the most stable pH range of 6.0–6.5, the half‐lives of B, C, and R in BU‐LM were 22, 15, and 20 days at 80 °C but 4510, 1717, and 3300 days at 25 °C, whereas for BU‐S only 11, 3, and 10 days at 80 °C and 71, 18, and 49 days at 25 °C. The results indicated that BU‐LM significantly increased the chemical stability of bufadienolides, especially at low temperatures. The degradation of bufadienolides took place mostly in the aqueous phase and the diffusion process of bufadienolides from the oil phase through the interfacial layer to the aqueous phase was the rate‐limiting step for the drug degradation. A low temperature slowed down of the diffusion rate leading to a slower degradation and longer half‐lives. Among the three bufadienolides in BU‐LM, C was protected from degradation to the greatest extent. Practical applications : Bufadienolides, consisting of bufalin (B), cinobufagin (C), and resibufogenin (R) have poor aqueous solubility between 20 and 60 µg/mL and are easily degradable by acids or bases. Here we propose a new strategy to overcome stability problems by using lipid microspheres (LM) as the drug vehicle. By incorporating the drugs into the interior oil phase and the oil–water interfacial film, a direct contact of the drug with body fluids and tissues is avoided. Thus the drug is protected from degradation and possible side effects are minimized. Our results indicate that BU‐LM significantly increased the chemical stability of bufadienolides, especially at low temperatures. Among the three bufadienolides in BU‐LM, C was protected from degradation to the greatest extent.     

Influence of H4SiW12O40 loading on hydrocracking activity of non-sulfide Ni-H4SiW12O40/SiO2 catalysts

The effect of H₄SiW₁₂O₄₀ loading on the catalytic performance of the reduced Ni-H₄SiW₁₂O₄₀/SiO₂ catalysts for hydrocracking of n-decane with or without the presence of thiophene and pyridine is studied. The catalysts were characterized by BET, XRD, Raman, XPS, H₂-TPR, H₂-TPD, NH₃-TPD and FT-IR of pyridine adsorption. It was found that addition of H₄SiW₁₂O₄₀ to the system increases the catalytic activity and the promoting effect is a function of the H₄SiW₁₂O₄₀ loading. The best result was obtained on 5%Ni-50%H₄SiW₁₂O₄₀/SiO₂ catalyst which shows the highest activity for hydrocracking of n-decane and excellent tolerance to the sulfur and nitrogen compounds in the feedstock. The results showed that a suitable amount of H₄SiW₁₂O₄₀ loading on the 5%Ni/SiO₂ catalyst increases the amount of both hydrogen adsorbed and Brønsted acid and Lewis acid sites on the catalyst. The high catalytic performance of the catalyst can be related to the nature of H₄SiW₁₂O₄₀ and the proper balance between metal and acid functions.     

Advanced anticorrosive coatings prepared from electroactive polyimide-TiO2 hybrid nanocomposite materials

In this study, we present the first preparation and corrosion protection studies of a series of electroactive polyimide-TiO₂ (EPTs) hybrid nanocomposite materials containing conjugated segments of electroactive amino-capped aniline trimer (ATs) and TiO₂ nanoparticles of ∼10 nm in diameter. Redox behavior of as-prepared EPTs hybrid materials was identified by electrochemical cyclic voltammetry (CV) studies. Higher concentration of TiO₂ component in as-prepare corresponding EPTs was found to reveal better corrosion protection effect on cold-rolled steel (CRS) electrode based on sequential electrochemical corrosion measurements in 5 wt.% NaCl electrolyte. Enhancement of corrosion protection of EPTs coatings on CRS electrode could be interpreted by following three possible reasons: (1) Electroactive polyimide (EPI) could act as a physical barrier coating. (2) The redox catalytic capabilities of ATs units existed in EPTs may induce the formation of passive metal oxide layers on CRS electrode. (3) The well-dispersed TiO₂ nanoparticles in EPTs matrix could act as effective hinder to enhance the oxygen barrier property of EPTs.     

Adaptation to Endoplasmic Reticulum Stress Enhances Resistance of Oral Cancer Cells to Cisplatin by Up-Regulating Polymerase η and Increasing DNA Repair Efficiency

Endoplasmic reticulum (ER) stress response is an adaptive program to cope with cellular stress that disturbs the function and homeostasis of ER, which commonly occurs during cancer progression to late stage. Late-stage cancers, mostly requiring chemotherapy, often develop treatment resistance. Chemoresistance has been linked to ER stress response; however, most of the evidence has come from studies that correlate the expression of stress markers with poor prognosis or demonstrate proapoptosis by the knockdown of stress-responsive genes. Since ER stress in cancers usually persists and is essentially not induced by genetic manipulations, we used low doses of ER stress inducers at levels that allowed cell adaptation to occur in order to investigate the effect of stress response on chemoresistance. We found that prolonged tolerable ER stress promotes mesenchymal–epithelial transition, slows cell-cycle progression, and delays the S-phase exit. Consequently, cisplatin-induced apoptosis was significantly decreased in stress-adapted cells, implying their acquisition of cisplatin resistance. Molecularly, we found that proliferating cell nuclear antigen (PCNA) ubiquitination and the expression of polymerase η, the main polymerase responsible for translesion synthesis across cisplatin-DNA damage, were up-regulated in ER stress-adaptive cells, and their enhanced cisplatin resistance was abrogated by the knockout of polymerase η. We also found that a fraction of p53 in stress-adapted cells was translocated to the nucleus, and that these cells exhibited a significant decline in the level of cisplatin-DNA damage. Consistently, we showed that the nuclear p53 coincided with strong positivity of glucose-related protein 78 (GRP78) on immunostaining of clinical biopsies, and the cisplatin-based chemotherapy was less effective for patients with high levels of ER stress. Taken together, this study uncovers that adaptation to ER stress enhances DNA repair and damage tolerance, with which stressed cells gain resistance to chemotherapeutics.     

N3-Kethoxal-Based Bioorthogonal Intracellular RNA Labeling

There is growing interest in developing intracellular RNA tools. Herein, we describe a strategy for N₃-kethoxal (N₃K)-based bioorthogonal intracellular RNA functionalization. With N₃K labeling followed by an in vivo click reaction with DBCO derivatives, RNA can be modified with fluorescent or phenol groups. This strategy provides a new way of labeling RNA inside cells.     

A gas chromatography–mass spectrometry method for the detection of chlorpyrifos contamination in palm-based fatty acids

Chlorpyrifos is a Malaysian Pesticide Board-approved organophosphate insecticide, which may become concentrated during fractionation. The objective of this project was to develop and validate a method to detect and quantify chlorpyrifos in food-grade fatty acids ingredients, e.g. caprylic-capric acid mixture and oleic acid (OLA) used to synthesize triacylglyceride based food additives and in the cosmetic industry. A selective ion monitoring gas chromatography–mass spectrometry method with a matrix-matched calibration curve calibration was selected. The method involved the direct injection of chlorpyrifos spiked into the fatty acids matrix. The percentage recoveries at spiking levels of 0.5, 0.75, 2.5, and 4.0 μg g⁻¹ of chlorpyrifos in OLA and caprylic-capric acid ranged from 85.7%–101.1% to 97.2%–112%, respectively, with a relative standard deviation of within 11%. The intra-day and inter-day precision were deemed acceptable as indicated by an relative SD value of within 10%. A good linear relationship with a coefficient of correlation >0.99 for the matrix-matched calibration was achieved between 0.5 and 5 μg g⁻¹. The limit of detection and limit of quantification corresponded to 0.5 μg g⁻¹ for OLA and 0.55 μg g⁻¹ for caprylic-capric acid.     

Effect of special structure of clam shell powder on structure and properties of castor oil-based composites

Castor oil (CO) is an environmentally friendly renewable green resource and ideal alternative to petroleum resources. The preparation of high strength and high toughness castor oil-based polyurethane prepolymer (COPU) composites has significant applications such as supporting material and engineering plastic sheet. In this study, unmodified clam shell powder (CSP) with a unique CaCO₃-proteoglycan structure was used as a filler to prepare compatible reinforced COPU composite materials. Investigation of the mechanical properties revealed that the elastic modulus of the composite COPU reinforced with 50 wt% of CSP had increased to 5859.0 ± 8.4 MPa representing 187.77% to obtain stiffer and stronger material over pure COPU (2036.6 ± 196.9 MPa). Moreover, the scanning electron microscopy, thermogravimetric analysis and contact angle results demonstrated that the reinforced COPU composites have better compatibility, thermal stability, and water resistance than pure COPU. This work will promote the application prospects of CO-based polyurethane.