Preparation and Cytotoxicity of Poly(Methyl Methacrylate) Nanoparticles for Drug Encapsulation

Summary: This work aimed to produce poly(methyl methacrylate) nanoparticles for use in drug encapsulation. The polymer nanoparticles were produced using miniemulsion polymerization technique. Monomer miniemulsion showed moderate stability and polymer average particle size was about 90 nm. PMMA nanoparticles were tested for toxicity in human leukemic cell strain K562 and they did not show any adverse effect on cell viability. Therefore, poly(methyl methacrylate) nanoparticles are suitable to encapsulate antitumor agents.     

Organocatalytic Control over a Fuel-Driven Transient-Esterification Network**

Signal transduction in living systems is the conversion of information into a chemical change, and is the principal process by which cells communicate. In nature, these functions are encoded in non-equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. However, man-made catalytically controlled networks are rare. We incorporated catalysis into an artificial fuel-driven out-of-equilibrium CRN, where the forward (ester formation) and backward (ester hydrolysis) reactions are controlled by varying the ratio of two organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. This fuel-driven strategy was expanded to a responsive polymer system, where transient polymer conformation and aggregation are controlled through fuel and catalyst levels. Altogether, we show that organocatalysis can be used to control a man-made fuel-driven system and induce a change in a macromolecular superstructure, as in natural non-equilibrium systems.     

Comparative bioavailability of two zolpidem hemitartrate formulations in healthy human Brazilian volunteers using high-performance liquid chromatography coupled to tandem mass spectrometry

To assess the bioequivalence of two zolpidem hemitartrate formulations in 30 healthy volunteers. Plasma samples were obtained over a 24 h period. Plasma concentrations of zolpidem were analyzed by liquid chromatography coupled to tandem mass spectrometry with positive ion electrospray ionization using multiple reaction monitoring. Values of peak concentration (C_max), area under curve (AUC), half-life, elimination constant, volume of distribution and clearance showed statistically significant differences when comparing women (604.34 ng h/ml, 127.36 ng/ml, 4.4 h, 0.18 1/h, 50.56 L and 8.55 L/h, respectively) and men (276.1 ng h/ml, 70.9 ng/ml, 3.3 h, 0.26 1/h, 91.42 L and 24.34 L/h, respectively), receiving the same dose (5 mg), respectively. The geometric means with corresponding 90% confidence interval for Test/Reference percentage ratios were 99.73% (CI 93.69–106.16) for C_max, 97.44% (90% CI = 91.85–103.37%) for area under curve of plasma concentration until the last concentration observed (AUC_last) and 98.30% (90% CI = 92.48–104.49) for the area under curve between the first sample (pre-dosage) and infinity (AUC_0–inf). Since the 90% CI for AUC_last, AUC_0–inf and C_max ratios were within the 80–125% interval proposed by the US Food and Drug Administration, it was concluded that zolpidem hemitartrate formulation (5 mg orodispersible tablet) is bioequivalent to the zolpidem hemitartrate formulation (Patz SL 5 mg sublingual tablet) with regard to both the rate and the extent of absorption. A new formulation of zolpidem 2.5 mg may be useful in women for the same clinical benefits as the 5 mg formulation in men.     

Fischer-Tropsch synthesis on anchored Co/Nb2O5/Al2O3 catalysts: the nature of the surface and the effect on chain growth

A series of Co/x%Nb2O5/Al2O3 catalysts were prepared by anchoring niobia on an Al2O3 support at different niobia concentrations. Characterization of the structure and nature of surface active sites was attempted in order to correlate the CO hydrogenation activity of these systems with those of the Co/Al2O3 and Co/Nb2O5 catalysts. The effect of the reduction temperature on the CO hydrogenation activity and selectivity was studied, showing that interaction of cobalt and niobia surface species favored the selectivity for hydrocarbon chain growth. However, this effect is less pronounced on the niobia-promoted Co/Al2O3 compared to Co/Nb2O5 catalysts. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS) results on Co/x%Nb2O5/Al2O3 showed prevailing amounts of Co2+ and Co3+ after calcination and reduction at 573 K, while, after reduction at 773 K, besides metallic cobalt, the Co2+ species still remains in contact with alumina, even for higher niobia loading. It seems that during this process formation and destruction of new interfaces involving Co0-NbOx sites takes place. Results suggest that Co0, Co0-Co2+, and Co0-NbOx are the active sites at the surface. The relative abundance of Co2+ species affects greatly the performance of the catalysts. DRIFTS and selectivity results suggest that these sites might be responsible for the reaction chain growth and therefore for the drastic change in the selectivity of CH4 and C5+ hydrocarbons mainly on the Co/Nb2O5 catalyst. DRIFTS results on Co/Nb2O5/Al2O3 showed the formation of -C=C- and -CH3- besides CHxO species. With increasing reduction temperature, the -C=C- species disappear while -CH3- fragments increased markedly, suggesting the formation of increasing amounts of hydrocarbons with higher chain length.     

Non-conventional oils for biodiesel production: a study of thermal and oxidative stability

Vegetable oils with variable proportions of oleic, linoleic, and linolenic acids are more susceptible to oxidative processes. In this subject, this study evaluates the physical chemical properties and oxidative stability of non-conventional oils such as andiroba, babassu, sesame, oiticica, jatropha, and grape through accelerated oxidation techniques (pressurized differential scanning calorimetry, Rancimat and PetroOxy). It was verified that babassu and andiroba oil do not showed detectable induction period presenting high oxidative stability; moreover, it was observed that the enthalpic events occurred in 1.19, >10, 0.53, 0.49, 0.49, and 0.60 h for the andiroba oil, babassu oil, sesame seeds, jatropha, oiticica oils, and grapes, respectively, stimulating the conclusion of greater stability for the babassu oil.     

Recycled high-density polyethylene/gypsum composites: evaluation of the microscopic,thermal, flammability,and mechanical properties

Sustainable composites comprising scraps of high-density polyethylene (HDPE) and gypsum waste in proportions HDPE/gypsum 100/0, 50/50, 40/60, and 30/70 wt% were prepared. The morphology of the injected specimens was core-shell. Thermal, flammability, water absorption, and compression resistance were also evaluated. Progressively, the presence of gypsum increased the HDPE crystallinity and T_onset. Concerning the flammability, the composite 30/70 exhibited the burning rate three times lower than HDPE, indicating that the gypsum played a role as a flame retardant. The HDPE acted as waterproofing for gypsum. The compression resistance of the composites was similar to HDPE.     

Influence of lanthanum exchange on the catalytic properties of HY zeolite in cyclohexene transformation

Cyclohexene transformation was used as test reaction to study the effect of lanthanum exchange on the catalytic behavior of HY zeolite cracking catalysts. Lanthanum has an overall positive effect increasing both acitivity and stability of HY zeolite and maximum selectivity towards isomerization products is obtained at higher conversion.

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Temperature dependent Raman scattering study of l-ascorbic acid

Temperature dependent Raman study of l-ascorbic acid has been performed from 15 to 418 K. Changes in the wavenumber vs. temperature plots for some internal modes were interpreted as conformational molecular change and the discontinuity in the wavenumber vs. temperature plots along with the appearance of a new vibrational mode in the temperature range 200-270 K suggests that l-ascorbic acid undergoes a structural phase transition. For temperatures higher than 300 K, no relevant modification was observed on the Raman spectra thus indicating a stable structure at high temperatures. Additionally, a correlation between OH stretching wavenumber and the behavior of hydrogen bond is also made.     

Determination of organophosphorous pesticides in the ppq range using a simple solid-phase extraction method combined with dispersive liquid-liquid microextraction

Solid-phase extraction combined with dispersive liquid-liquid microextraction (SPE-DLLME) was applied for the extraction of six organophosphorous pesticides (OPPs) in water samples. The analytes considered in this study were determined by gas chromatography with mass spectrometry and included prophos, diazinon, chlorpyrifos methyl, methyl parathion, fenchlorphos and chlorpyrifos. Several extraction conditions (extraction solvent and elution/dispersion solvents nature, extraction solvent volume, elution solvent volume, water volume and sample volume) were tested for SPE-DLLME with these analytes and the best results were obtained using carbon tetrachloride as the extraction solvent and acetone as the elution/dispersion solvent. Calibration curves for the determination of OPPs in water samples were constructed in the concentration range of 10-100 ng/L. Limits of detection (LODs) ranged from 38 to 230 pg/L values that are below the maximum admissible level for drinking water (100 ng/L). Relative standard deviations (RSD) were between 8.6 and 10.4% for a fortification level of 100 ng/L. At the same fortification level, the relative recoveries (R.R.) of tap, well and irrigation water samples were in the range of 30.2-97.1%.