Superparamagnetic poly(methyl methacrylate) nanoparticles surface modified with folic acid presenting cell uptake mediated by endocytosis

The encapsulation of superparamagnetic nanoparticles (MNPs) in polymeric nanoparticles (NPs) with modified surfaces can improve targeted delivery and induce cell death by hyperthermia. The goals of this study were to synthesize and characterize surface modified superparamagnetic poly(methyl methacrylate) with folic acid (FA) prepared by miniemulsion polymerization (MNPsPMMA-FA) and to evaluate their in vitro cytotoxicity and cellular uptake in non-tumor cells, murine fibroblast (L929) cells and tumor cells that overexpressed folate receptor (FR) β, and chronic myeloid leukemia cells in blast crisis (K562). Lastly, hemolysis assays were performed on human red blood cells. MNPsPMMA-FA presented an average mean diameter of 135 nm and a saturation magnetization (Ms) value of 37 emu/g of iron oxide, as well as superparamagnetic behavior. The MNPsPMMA-FA did not present cytotoxicity in L929 and K562 cells. Cellular uptake assays showed a higher uptake of MNPsPMMA-FA than MNPsPMMA in K562 cells when incubated at 37 °C. On the other hand, MNPsPMMA-FA showed a low uptake when endocytosis mechanisms were blocked at low temperature (4 °C), suggesting that the MNPsPMMA-FA uptake was mediated by endocytosis. High concentrations of MNPsPMMA-FA showed hemocompatibility when incubated for 24 h in human red blood cells. Therefore, our results suggest that these carrier systems can be an excellent alternative in targeted drug delivery via FR.     

Two-part fractional regression model with conditional FDH responses: an application to Brazilian agriculture

We extend the notion of a two-part fractional regression model with conditional free disposal hull efficiency responses to accommodate two-stage regression analysis. The two-part regression model includes the binomial model with a nonlinear specification for the expected response in (0,1] and is a more general formulation in the context of fractional regressions. We use nonlinear least squares to assess the effect of covariates in the conditional efficiency response. The approach is applied to Brazilian agricultural county data, as reported in the Brazilian agricultural census of 2006. The efficiency measure is output oriented and assumes variable returns to scale. Output is rural gross income and inputs are land expenses, labor expenses and expenses on other technological inputs. The covariates affecting production are credit, technical assistance, a rural development index, income concentration, measured by the Gini index, and regional dummies. Overall Brazilian rural production performance responds positively to all covariates.

     

The Synthesis and Photoisomerization of 5-Methyl-5-Vinyl-1,3-Cyclopentadiene

A versatile scheme for the synthesis of geminally disubstituted cyclopentadienes is used to prepare the title compound 4 . This remarkably stable vinyl-cyclopentadiene, distinguished by its C_s symmetry, undergoes exclusively electrocyclic ring closure upon direct π–π* excitation at 254 nm. The epimeric vinyl-housenes 11 and 12 , which, for geometric reasons, are insensitive to the walk rearrangement, are suggested to be the primary photo-products. One of them, 12 , due to its syn-oriented vinyl group, undergoes spontaneous copy rearrangement to give 2-methylbicyclo[3.2.1]hepta-2,6-diene ( 13 ). The other, 11 , having an anti-oriented vinyl group, can only undergo thermal return to the starting material 4 . Whereas no leakage to a 1,5-vinyl migration is discernible for the S₁ state of 4 , the benzophenone-sensitized photolysis at 350 nm is shown to be governed by this rearrangement. 1-Methyl-5-vinylcyclopenta-1,3-diene ( 14 ), the unstable primary product of the sensitized photoreaction, is trapped by 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione (PTAD).     

Effets de substituant,d'hétéroatome et de solvant sur les cinétiques de décoloration thermique et les spectres d'absorption de photomérocyanines en série spiro[indoline-oxazine]

Substituent, Heteroatom, and Solvent Effects on the Thermal-Bleaching Kinetics and Absorption Spectra of Photomerocyanines Issued from Spiro[indoline-oxazines] Quantitative information useful for the development of new photochromic systems is obtained from the study of heteroatom and substituent effects on the thermal-bleaching kinetics and the absorption spectra of the photomerocyanines issued from spiro[indoline-oxazines]. The effect on photochromic properties of the presence of N-atoms either in the dimethine bridge or in the aromatic rings has been investigated through the comparison of spiro[indoline-naphthopyrans] C with spiro[indoline-naphthoxazines] A and with spiro[indoline-quinolinoxazines] B . Besides the occurrence of biexponential thermal-bleaching kinetics in non-polar solvents is observed: a tentative explanation for this observation is given which involves the formation, in either sequential or parallel steps, of energetically distinct stereoisomers of the opened form.     

AFM investigation of Pseudomonas aeruginosa lectin LecA (PA-IL) filaments induced by multivalent glycoclusters

Atomic force microscopy reveals that Pseudomonas aeruginosa LecA (PA-IL) and a tetra-galactosylated 1,3-alternate calix[4]arene-based glycocluster self-assemble according to an aggregative chelate binding mode to create monodimensional filaments. Lectin oligomers are identified along the filaments and defects in chelate binding generate branches and bifurcations. A molecular model with alternate 90° orientation of LecA tetramers is proposed to describe the organisation of lectins and glycoclusters in the filaments.     

Application of multivariate techniques in the optimization of a procedure for the determination of bioavailable concentrations of Se and As in estuarine sediments by ICP OES using a concomitant metals analyzer as a hydride generator

A procedure has been developed for the determination of bioavailable concentrations of selenium and arsenic in estuarine sediments employing inductively coupled plasma optical emission spectrometry (ICP OES) using a concomitant metals analyzer device to perform hydride generation. The optimization of hydride generation was done in two steps: using a two-level factorial design for preliminary evaluation of studied factors and a Doehlert design to assess the optimal experimental conditions for analysis. Interferences of transition metallic ions (Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺ and Ni²⁺) to selenium and arsenic signals were minimized by using higher hydrochloric acid concentrations. In this way, the procedure allowed the determination of selenium and arsenic in sediments with a detection limit of 25 and 30 μg kg⁻¹, respectively, assuming a 50-fold sample dilution (0.5 g sample extraction to 25 mL sample final volume). The precision, expressed as a relative standard deviation (% RSD, n = 10), was 0.2% for both selenium and arsenic in 200 μg L⁻¹ solutions, which corresponds to 10 μg g⁻¹ in sediment samples after acid extraction. Applying the proposed procedure, a linear range of 0.08-10 and 0.10-10 μg g⁻¹ was obtained for selenium and arsenic, respectively. The developed procedure was validated by the analysis of two certified reference materials: industrial sludge (NIST 2782) and river sediment (NIST 8704). The results were in agreement with the certified values. The developed procedure was applied to evaluate the bioavailability of both elements in four sediment certified reference materials, in which there are not certified values for bioavailable fractions, and also in estuarine sediment samples collected in several sites of Guanabara Bay, an impacted environment in Rio de Janeiro, Brazil.     

Direct determination of manganese in produced waters from petroleum exploration by Electrothermal Atomic Absorption Spectrometry using Ir-W as permanent modifier

This present work reports the development and evaluation of a method for the direct determination of manganese in waters extracted during petroleum exploitation by Electrothermal Atomic Absorption Spectrometry (ET AAS) using Ir-W as permanent modifier. These waters, usually called produced waters, contain a wide range of organic and inorganic substances and are characterized by their high salinity. In order to achieve suitable experimental conditions for the method application, studies about the effect of operational variables (chemical modifier, pyrolysis and atomization temperatures) were performed, as well as the establishment of convenient calibration strategy. The best results were verified when the temperatures of pyrolysis and atomization were 1000 °C and 2300 °C, respectively, and using Ir-W as permanent modifier. The results showed that manganese can be determined by the standard addition method or employing external calibration with standard solutions prepared in the same salinity of the samples (with NaCl). Three real samples with salinities varying between 74 and 84‰ were successfully analyzed by the developed procedure. The limits of detection and quantification were 0.24 and 0.80 μg L⁻¹, respectively, in purified water, and 0.34 and 1.1 μg L⁻¹, respectively, in 0.4 mol L⁻¹ NaCl medium (approximately 23‰ salinity).     

Influence of the compatibilizer polarity and molar mass on the morphology and the gas barrier properties of polyethylene/clay nanocomposites

In this study, different modified polyethylenes with different molar masses and different modification rates were examined as compatibilizers to prepare high density polyethylene/organoclay nanocomposites. Nanocomposites having 5 wt % organo-modified clay and 20 wt % interfacial agent were prepared by melt blending. The effect of compatibilizer molar mass and polarity was investigated on the clay dispersion and on the gas barrier properties. It was observed that the amount of large and dense fillers aggregates was considerably reduced by introduction of an interfacial agent. The nanocomposite final morphology was governed by a diffusion/shear mechanism. A high degree of clay delamination was obtained with the high molar mass compatibilizers, whereas highly swollen clay aggregates resulted from the incorporation of the low molar mass interfacial agents. In the investigated nanocomposites series, the barrier properties could not be directly related to the clay dispersion state but resulted also from the matrix/clay interfacial interactions. A gas transport mechanism based on these both parameters was proposed to explain the barrier properties evolution in these low polar nanocomposites series. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2593–2604, 2008     

Synthesis of Homo- and Heterofunctionalized Glycoclusters and Binding to Pseudomonas aeruginosa Lectins PA-IL and PA-IIL

Homo- and heterofunctionalized glycoclusters with galactose and/or fucose residues targeting both PA-IL and PA-IIL lectins of Pseudomonas aeruginosa were synthesized using "Click" chemistry and DNA chemistry. Their binding to lectins (separately or in a mixture) was studied using a DNA Directed Immobilization carbohydrate microarray. Homoglycoclusters bind selectively to their lectin while the heteroglycocluster binds simultaneously both lectins with a slight lower affinity.     

Voltammetric Determination of Folic Acid Using a Graphite Paste Electrode

A simple differential pulse voltammetric method based on a graphite paste electrode (GPE) was developed for the quantitative determination of folic acid (FA) in tablets. The electrode exhibits a clear improvement of the current response. A linear response in the electroanalytical approach exists from 4.97×10^?6 to 2.94×10^?5 mol L^?1 with a limit of detection of about 2.67×10^?6 mol L^?1 in KCl solutions. The developed procedure was tested by recovery studies and compared with spectrophotometric and chromatographic methods. The results are described and discussed in the light of existing literature.