Migration of α-tocopherol from LDPE films to corn oil and its effect on the oxidative stability

The migration of α-tocopherol (α-T) from low density polyethylene (LDPE) films, added with 20 (film A) and 40 mg g^?1 (film B) to corn oil for 12 weeks at 5, 20 and 30 °C was determined. A LDPE film added with no α-T was used as control (film C). Diffusion coefficient (D) values for the film A system were 1.4 × 10^?11, 7.1 × 10^?11 and 30.3 × 10^?11 cm² s^?1 at 5, 20 and 30 °C, respectively. Meanwhile, D values for the film B system were 1.3 × 10^?11, 9.6 × 10^?11 and 51.1 × 10^?11 cm² s^?1 at the same temperatures. The activation energy (E_a) for the diffusion of α-T was 126.5 (film A) and 105.9 kJ mol^?1 (film B). The effect of the migration of α-T on the oxidative stability of corn oil was evaluated by monitoring hexanal content by solid phase micro-extraction (SPME) and gas chromatography. The hexanal content in the oil showed that both films added with α-T resulted suitable to maintain the oxidative stability of the oil for about 16 weeks at 30 °C, compared to 12 weeks for the oil in contact with the film C.     

Size-dependent antimicrobial properties of sugar-encapsulated gold nanoparticles synthesized by a green method

The antimicrobial properties of dextrose-encapsulated gold nanoparticles (dGNPs) with average diameters of 25, 60, and 120 nm (± 5) and synthesized by green chemistry principles were investigated against both Gram-negative and Gram-positive bacteria. Studies were performed involving the effect of dGNPs on the growth, morphology, and ultrastructural properties of bacteria. dGNPs were found to have significant dose-dependent antibacterial activity which was also proportional to their size. Experiments revealed the dGNPs to be bacteriostatic as well as bactericidal. The dGNPs exhibited their bactericidal action by disrupting the bacterial cell membrane which leads to the leakage of cytoplasmic content. The overall outcome of this study suggests that green-synthesized dGNPs hold promise as a potent antibacterial agent against a wide range of disease-causing bacteria by preventing and controlling possible infections or diseases.     

Tannins, phytic phosphorus, phytase activity in the seed of 12 sorghum grain hybrids (Sorghum bicolor (L) Moench)

In order to evaluate the variability in concentration of secondary metabolites among grains from different sorghum hybrids (Sorghum bicolor (L) Moench) and provide some information for rational use in animal feeds, grain samples were collected from 12 hybrids (Criollo 1, Criollo 27, Chaguaramas III, Chaguaramas VII, Cristiani Burkard H-8046-2, Guanipa 95, Himeca 101, Himeca 400, Pioneer 81-G67, Pioneer 83-G88, Pioneer 86-P42 y Tecsem 120) sowed on 2008 in the Turén municipality, Portuguesa State-Venezuela. Using standardized analytical methods, hybrids showed polyphenolics compounds contents (0.92 +/- 0.37% TaE), total (0.61 +/- 0.29% TaE) and condensed tannins (0.95 +/- 0.65% LeuE), phytic phosphorus (0.17 +/- 0.03%) and intrinsic phytase activity (12.3 +/- 6.74 U/kg) in the ranges described in the literature, with an important variation among hybrids that must be considered for their inclusion levels in the formulation of balanced feeds, as well as plant breeding programs.     

Sensitivity of single wall carbon nanotubes to oxidative processing: structural modification, intercalation and functionalisation

The effect of oxidation on modification of single wall carbon nanotubes (SWCNTs) through successive purification steps has been studied. The efficient elimination of metal impurities has been followed by induced coupled plasma spectroscopy. Upon acid treatment, Raman spectroscopy clearly proofed that HNO₃ molecules were intercalated into the bundles of SWCNTs. At the same time, SWCNTs also have suffered a high degree of degradation and defects were introduced. The subsequent thermal processes led to the removal of further defect carbon materials and to the almost complete de-intercalation of the HNO₃ molecules. Changes in the structure of the SWCNT bundles have been observed by transmission electron microscopy. While bundles tend to separate upon acid treatment, after the complete purification process, the remaining SWCNTs tend to form thick bundles again. The existence of functional groups in the raw single wall carbon nanotubes material and their modification and almost complete removal after the final annealing step has been studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and temperature programmed desorption. Nitrogen adsorption isotherms analysed according to Brunauer-Emmet-Teller showed important changes in the pore volume and surface area through the purification steps.     

Heavy metal removal with Mexican clinoptilolite: multi-component ionic exchange

This paper describes the interactions of Pb(II), Cd(II), and Cr(VI) competing for ion-exchange sites in naturally occurring clinoptilolite. Dissolved Pb and Cd were effectively removed within 18 h in batch reactors, with higher removal efficiencies (> 95%) in the acidic pH range. The presence of Cr(VI), which can interact with these metals to form anionic complexes, significantly diminished the Pb and Cd removal efficiencies. A decrease in the efficiency of clinoptilolite to remove Pb was also observed in the high (> or = 10) pH range. This was attributed to the formation of anionic hydroxo-complexes with little affinity for cationic ion exchange sites. Pb outcompeted Cd for ion exchange sites in a flow-through column packed with clinoptilolite (contact time = 10 s). The preferential removal of Pb in column, but not in batch reactors, reflects that competitive retention can be affected by contact time because diffusion kinetics may influence the removal efficiency to a greater extent than equilibrium partitioning. Phenol, which was tested as a representative organic co-contaminant, slightly hindered heavy metal removal in batch reactors. This was attributed to the formation of organometallic complexes that cannot penetrate the zeolite exchange channels. Altogether, these results show that natural zeolites hold great potential to remove cationic heavy metal species from industrial wastewater. Nevertheless, process efficiency can be hindered by the presence of ligands that form complexes with reduced accessibility and/or affinity for ion exchange.     

Takayasu's arteritis as a cause of renovascular hypertension in a non-Asian population

Takayasu's disease (TD) is a chronic inflammatory arteritis which affects the aorta and its main branches and occasionally the pulmonary artery. Its cause is not known. Clinical manifestations are due to the intensity and location of arterial inflammation in the acute phase, as well as chronic arterial stenosis over time; 50% of patients have hypertension. Although TD appears to be more common in Asia, increasing numbers of patients of different races are observed in Western countries. The most important pathogenetic mechanism of hypertension seems to be through renal artery stenosis. We show here seven Caucasian hypertensive patients with TD and renovascular stenosis and arterial hypertension. One case was diagnosed in the acute phase of the disease, while in the others diagnosis was established in an advanced occlusive phase. Basic diagnosis was established by angiographic study, with biopsy confirmation in two cases. All patients had at least three of the six criteria listed as diagnostic of TD (by the American College of Reumatology). All patients had the following criteria: age of disease onset before 40 years (symptoms or findings related to TD), vascular bruits in different areas and all patients also had aortic and renal arterial stenosis with some lesions of the main aortic branches. Six of them had claudication of the extremities. We describe their clinical, analytical and angiographic features and also the therapeutic approach. We discuss the aetiopathogenic mechanisms of hypertension in this disease and suggest that TD is not an unusual cause of vasculorenal hypertension.     

Immobilized enzyme-linked DNA-hybridization assay with electrochemical detection for Cryptosporidium parvum hsp70 mRNA

An electrochemical enzyme-linked immobilized DNA-hybridization assay for the detection of Cryptosporidium parvum in water has been developed. The target molecule was a 121-nucleotide sequence from the C. parvum heat shock protein 70 (hsp70 mRNA from U71181 gene). This analyte offers the possibility of distinguishing dead from live oocysts. The assay involves covalent attachment of a primary DNA probe via its 5'-amine-terminus to self-assembled monolayers of mercaptoundecanoic acid to a gold surface. The primary DNA probe was used to capture the target (sequence 1039-1082 of U71181 gene for the mRNA), by hybridization to a 20-base complementary sequence on the target (at sequence 1063-1082). A secondary DNA probe labeled with alkaline phosphatase (AP) was then hybridized to base sequence 1039-1062 on the target. p-Aminophenol, which is enzymatically generated by the immobilized AP from p-aminophenyl phosphate (PAPP), is detected using electrochemistry. The peak current of cyclic voltammograms from a PAPP solution, in which gold-coated silicon wafer modified with the complete assembly of the assay components was incubated, is linear with concentration of the target (5-50 microg/mL, where P1 and P2-AP concentrations are 50 microg/mL). A detection limit of 2 microg/mL (or 146 nM) of the DNA target was obtained. Cross-reactivity tests showed high selectivity for heat-shocked C. parvum. No signal was obtained for either the synthetic DNA for hsp70 of Campylobacter lari, Escherichia coli, Giardia lamblia, Salmonella typhimurium, and Listeria monocytogenes or for the products of heat-shocked whole organisms of E. coli, G. lamblia, Staphylococcus aureus, and Cryptosporidium muris.     

Self-contained microelectrochemical immunoassay for small volumes using mouse IgG as a model system

A self-contained, microelectrochemical immunoassay on the smallest volumes reported to date (1 microL for the antigen, 1 microL for the secondary antibody-enzyme conjugate, and 200 nL for the electrochemically detected species) has been developed using mouse IgG as a model system in a sandwich-type enzyme-linked immunosorbant assay, which takes less than 30 min to both complete the assembly of immunoassay components onto the antibody-modified surface and detect enzymatically generated species (excluding time for electrochemical cleaning of electrodes). These studies demonstrate the advantage of the close proximity of electrodes to modified surfaces and their application in the analysis of small volumes. Using a 50 microm diameter x 8 microm deep cavity with individually addressable electrodes on a microfabricated chip, the primary antibody was selectively and covalently attached at a gold, recessed microdisk (RMD) at the bottom of the microcavity to the free end of SAMs of either 11-mercaptoundecanoic acid or 11-mercapto-1-undecanol using 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride. Nonspecific adsorption to the surrounding material, polyimide, of the microcavity device was eliminated. Electrochemical desorption was used to confine the immunoassay activity at the RMD. Enzymatic conversion of the substrate p-aminophenyl phosphate top-aminophenol is detectable in less than 30 s using cyclic voltammetry at a gold, tubular nanoband electrode, which is on the wall of the microcavity and immediately adjacent to the modified RMD. A third electrode, also within the region of the microcavity, served as the pseudoreference/auxiliary electrode. Calibration curves obtained for 1-microL solutions of 5-100 ng/mL of IgG and for 200 nL-solutions of 5 microM to 4 mM of PAPR gave detection limits of 4.4 nM (6.4 ng/mL) or 880 fmol (129 pg) for PAPR and 56 fM (9 pg/mL) or 56 zmol (9 fg) for IgG. It is expected that the device may be suitable for analysis with volumes down to tens of picoliters.