Processing nanoparticles with A4F-SAXS for toxicological studies: Iron oxide in cell-based assays

Nanoparticles are not typically ready-to-use for in vitro cell culture assays. Prior to their use in assays, powder samples containing nanoparticles must be dispersed, de-agglomerated, fractionated by size, and characterized with respect to size and size distribution. For this purpose we report exemplarily on polyphosphate-stabilized iron oxide nanoparticles in aqueous suspension. Fractionation and online particle size analysis was performed in a time-saving procedure lasting 50 min by combining asymmetrical flow field-flow fractionation (A4F) and small-angle X-ray scattering (SAXS). Narrowly distributed nanoparticle fractions with radii of gyration (R(g)) from 7 to 21 nm were obtained from polydisperse samples. The A4F-SAXS combination is introduced for the preparation of well-characterized sample fractions originating from a highly polydisperse system as typically found in engineered nanoparticles. A4F-SAXS processed particles are ready-to-use for toxicological studies. The results of preliminary tests of the effects of fractionated iron oxide nanoparticles with a R(g) of 15 nm on a human colon model cell line are reported.     

1H, 13C and 15N NMR spectral assignments of adenosine derivatives with different amino substituents at C6-position

The complete (1)H, (13)C and (15)N NMR signals assignment of adenosine derivatives differently substituted at C(6)-position was achieved using one- and two-dimensional experiments (gs-COSY, gs-NOESY, gs-HSQC and gs-HMBC).     

Synthesis of enantiomerically pure (R)-and (S)-1-benzoyloxypropane-2,3-diol and revision of the stereochemical outcome of the Candida antarctica lipase-catalyzed benzoylation of glycerol

Enantiomerically pure (R)- and (S)-1-benzoyloxypropane-2,3-diol have been prepared from (S)-(+)-2,2-dimethyl-1,3-dioxolane-4-methanol and used as reference compounds to correct the reported stereochemical outcome of the Candida antarctica lipase (CAL)-catalyzed benzoylation of glycerol.     

Synthesis of Differently Protected 1‐C‐Methyl‐Ribofuranoses Intermediates for the Preparation of Biologically Active 1′‐C‐Methyl‐Ribonucleosides

Starting from D‐ribose, differently protected 1‐C‐methyl‐D‐ribofuranoses have been prepared as intermediates for the synthesis of variously modified 1′‐C‐methyl‐ribonucleosides, a class of compounds potentially endowed with interesting biological activity.     

Spherical aggregates obtained from N-carboxymethylation and acetylation of chitosan

Chitosan is a biopolymer with great industrial potential. However, solubility in aqueous solutions limits some applications. In this paper, the N-carboxymethylation (CM) of chitosan generated five derivatives namely, N-carboxymethylchitosan (NCMC) 1, NCMC2, NCMC3, NCMC4, and NCMC5, from 10.1% to 80% of CM. Afterwards, a new NCMC6 (∼60% of CM) was acetylated to produce the NCMCAc derivate. The modifications were confirmed by ¹³C nuclear magnetic resonance. A globular conformation to NCMC derivatives was confirmed by association of static and dynamic light scattering in which the form factor (ρ) is ∼1.3 in phosphate buffer (pH 7.4). The NCMCAc showed a ρ of 0.75, which is characteristic of dense spheres. Topographical analyses were performed by atomic force microscopy images in which dense spheres were observed. The critical aggregation concentration (CAC) was determined using pyrene as a hydrophobic fluorescent probe. For NCMC1–6 and NCMCAc, a CAC of 1.0 and 0.1 mg mL⁻¹ were, respectively, observed. NCMC1–6 and NCMCAc showed a globular and dense spherical conformation, respectively.     

Effects of natural convection on thermal explosion in a closed vessel

A new way of ascertaining whether or not a reacting mixture will explode uses just three timescales: that for chemical reaction to heat up the fluid containing the reactants and products, the timescale for heat conduction out of the reactor, and the timescale for natural convection in the fluid. This approach is developed for an nth order chemical reaction, A --> B occurring exothermically in a spherical, batch reactor without significant consumption of A. The three timescales are expressed in terms of the physical and chemical parameters of the system. Numerical simulations are performed for laminar natural convection occurring; also, a theoretical relation is developed for turbulent flow. These theoretical and numerical results agree well with previous experimental measurements for the decomposition of azomethane in the gas phase. The new theory developed here is compared with Frank-Kamenetskii's classical criterion for explosion. This new treatment has the advantage of separating the two effects inhibiting explosion, viz. heat removal by thermal conduction and by natural convection. Also, the approach is easily generalised to more complex reactions and flow systems.     

A structural study of the retinal photoreceptor, plexiform and ganglion cell layers following exposure to UV-B and UV-C radiation in the albino rat

Over the last two decades, ultraviolet radiation levels (UV), reaching the Earth's surface, have been increasing at a rate of 1.5% per each 1% loss of the ozone layer. Moreover, artificial UV-sources have also proliferated and contributed to the rising UV-stress that many organisms have to face. To assess how the vertebrate retina responds to an exposure of short wavelength UV, we focused our attention on the rat retina, observing photoreceptor (containing outer and inner segments of rods and cones), inner plexiform, and ganglion cell layers by light and transmission electron microscopy using conventional and cytochemical techniques. We analyzed how cells of the layers in question responded to a 30 min exposure to UV-C and UV-B radiation with doses of 7200 and 590 J/cm², respectively. The results show that there are significant changes in the nuclei and cytoplasmic organelles of the exposed retinae when compared with those of the unexposed controls. The changes include an increase in heterochromatin, distension of rough endoplasmic reticulum, mitochondrial disruptions, and increases in the number of myelin bodies. The recorded morphological changes, especially those of the ganglion cells, are suggestive of apoptotic processes and show that the exposure of vertebrate retina to wavelengths ranging from 254 to 312 nm can produce alterations that are likely to impact negatively on the retina's proper functioning.     

Influence of N-doping on the structure and electronic properties of titania nanoparticle photocatalysts

N-containing TiO(2)-based nanostructured materials (average particle size approximately 10 nm) with an anatase-type structure were investigated using oxygen (O) K-edge and titanium (Ti) K- and L-edge X-ray absorption near-edge spectroscopy (XANES). The Ti K pre-edge features indicate that samples predominantly contain ([6])Ti with some ([5])Ti, and there is no evidence for ([4])Ti. We observed that those samples with a larger fraction of Ti in a fivefold coordination, that is, with a significant number of oxygen vacancies, also present a modified Ti environment at the medium-range scale. The presence of these defects drastically modifies the electronic structure of the conduction band, as evidenced by the O K XANES spectra, but does not result in the presence of reduced Ti(3+) states. We discuss the influence of N-doping on titania nanoparticles and their structure, electronics and photocatalytic activity.     

Validation of the antifactor Xa and antifactor IIa assays for the potency assessment of nadroparin in pharmaceutical formulations

The low-molecular weight heparin nadroparin calcium is used clinically for the prevention and treatment of venous and arterial thrombosis. The antifactor Xa and antifactor IIa assays were validated by investigating the parameters of range, linearity (r2 = 0.9905 and r2 = 0.9914, respectively) precision, accuracy, and robustness. The 2 methods incorporated a chromogenic endpoint and detection at 405 nm, yielding good results with detection limits of 0.004 and 0.01 IU/mL and quantitation limits of 0.01 and 0.03 IU/mL, respectively, for the antifactor Xa and antifactor IIa assays. Nadroparin calcium pharmaceutical products were evaluated by the antifactor Xa assay and the antifactor IIa assay, giving potencies between 93.86 and 109.88%, with an antifactor Xa/antifactor IIa ratio between 3.2 and 3.7. The results demonstrated the validity of the assays that are useful methodologies for the routine quality control of nadroparin in pharmaceutical formulations.     

Unusual calibration curves observed for iron using high-resolution continuum source graphite furnace atomic absorption spectrometry

The simultaneous determination of cadmium and iron in plant and soil samples has been investigated using high-resolution continuum source graphite furnace atomic absorption spectrometry. The primary cadmium resonance line at 228.802 nm and an adjacent secondary iron line at 228.726 nm, which is within the spectral interval covered by the charge-coupled device (CCD) array detector, have been used for the investigations. Due to the very high iron content in most of the soil samples the possibility has been investigated to reduce the sensitivity and extend the working range by using side pixels for measurement at the line wings instead of the line core. It has been found that the calibration curves measured at all the analytically useful pixels of this line consisted of two linear parts with distinctly different slopes. This effect has been independent of the positioning of the wavelength, i.e., if the Cd line or the Fe line was in the center of the CCD array. The most likely explanation for this unusual behavior is a significant difference between the instrument width Δλ_Instr and the absorption line width Δλ_Abs, which is quite pronounced in the case of Fe. Using both parts of the calibration curves and simultaneous measurement at the line center and at the wings made it possible to extend the working range for the iron determination to more than three orders of magnitude.