Inorganic Nanoparticles and the Immune System: Detection, Selective Activation and Tolerance

The immune system is the responsible for body integrity and prevention of external invasion. On one side, nanoparticles are no triggers that the immune system is prepared to detect, on the other side it is known that foreign bodies, not only bacteria, viruses and parasites, but also inorganic matter, can cause various pathologies such as silicosis, asbestosis or inflammatory reactions. Therefore, nanoparticles entering the body, after interaction with proteins, will be either recognized as self-agents or detected by the immune system, encompassing immunostimulation or immunosuppression responses. The nature of these interactions seems to be dictated not specially by the composition of the material but by modifications of NP coating (composition, surface charge and structure). Herein, we explore the use of gold nanoparticles as substrates to carry multifunctional ligands to manipulate the immune system in a controlled manner, from undetection to immunostimulation. Murine bone marrow macrophages can be activated with artificial nanometric objects consisting of a gold nanoparticle functionalized with peptides. In the presence of some conjugates, macrophage proliferation was stopped and pro-inflammatory cytokines were induced. The biochemical type of response depended on the type of conjugated peptide and was correlated with the degree of ordering in the peptide coating. These findings help to illustrate the basic requirements involved in medical NP conjugate design to either activate the immune system or hide from it, in order to reach their targets before being removed by phagocytes. Additionally, it opens up the possibility to modulate the immune response in order to suppress unwanted responses resulting from autoimmunity, or allergy or to stimulate protective responses against pathogens.

Isolation of compounds attractive to the leaf-cutting ant Atta sexdens rubropilosa forel (hymenoptera: Formicidae) from Mabea fistulifera elaiosome

Mabea fistulifera (Euphorbiaceae)is a pioneer plant species with seeds dispersed by the ant Atta sexdens rubropilosa. Since the ants are attracted to the seeds to use its elaiosome as a source of energy, we investigated its composition. The elaiosomes from 13,000 seeds were extracted with a methanol:chloroform mixture (2:1 v/v) and yielded 22% of a residue. This residue was fractionated by column chromatography and its composition determined by infrared spectroscopy and chromatography/mass spectrometry (GC-MS). The elaiosome lipids are constituted mainly by free fatty acids, triacylglycerols and minor quantities of monoacylglycerols or diacylglycerols.

A multi-screening approach for marine-derived fungal metabolites and the isolation of cyclodepsipeptides from Beauveria felina

Extracts obtained from 57 marine-derived fungal strains were analyzed by HPLC-PDA, TLC and ¹H NMR. The analyses showed that the growth conditions affected the chemical profile of crude extracts. Furthermore, the majority of fungal strains which produced either bioactive of chemically distinctive crude extracts have been isolated from sediments or marine algae. The chemical investigation of the antimycobacterial and cytotoxic crude extract obtained from two strains of the fungus Beauveria felina have yielded cyclodepsipeptides related to destruxins. The present approach constitutes a valuable tool for the selection of fungal strains that produce chemically interesting or biologically active secondary metabolites.

Highly selective transport of mercury(II) ion through a bulk liquid membrane

In this work carrier-facilitated transport of mercury(II) against its concentration gradient from aqueous 0.04 M hydrochloric acid solution across a liquid membrane containing isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE) as the mobile carrier in chloroform has been investigated. Sodium thiocyanate solution (1.6 M) was the most efficient receiving phase agent among several aqueous reagents tested. Various parameters such as investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is more than 97% after 2.5 h. The carrier, IIDE, selectively and efficiently could able to transport Hg (II) ions in the presence of other associated metal ions in binary systems.

Low metal loading catalysts used for the selective hydrogenation of styrene

A series of Group VIII metal catalysts was obtained for the semi-hydrogenation of styrene. Catalysts were characterized by Hydrogen Chemisorption, TPR and XPS. Palladium, rhodium and platinum low metal loading prepared catalysts presented high activity and selectivity (ca. 98%) during the semi-hydrogenation of styrene, being palladium the most active catalyst. The ruthenium catalyst also presented high selectivity (ca. 98%), but the lowest activity. For the palladium catalyst, the influence of the precursor salt and of the reduction temperature on the activity and selectivity were studied. The following activity series was obtained: PdN-423 > PdCl-673 > PdCl-373> PtCl-673 > RhCl-673 >> RuCl-673. As determined by XPS, differences in activity could be attributed, at least in part, to electronic effects.

Selective hydrogenation of furfural on Ir/TiO2 catalysts

Titania-supported Ir catalysts were used in the hydrogenation of furfural. Reactions were carried out in a stirred batch type reactor at 0.62MPa and 363K using a 0.10M solution of furfural in a 1:1 mixture n-heptane -ethanol as solvent. Catalysts containing 2 wt% of Ir were reduced in H2 flow at different temperatures in the range 473-773K. The catalysts were characterized by H2 chemisorption, TEM, TPR, TPD of NH3 and XPS. Conversion of furfural is higher at lower reduction temperatures, but leads to byproducts whereas reduction at higher temperatures shows selectivity to furfuryl alcohol close to 100%.

Influence of ni addition to a low-loaded palladium catalyst on the selective hydrogenation of 1-heptyne

Semi-hydrogenation of alkynes has industrial and academic relevance on a large scale. To increase the activity, selectivity and lifetime of monometallic catalysts, the development of bimetallic catalysts has been investigated. 1-Heptyne hydrogenation over low-loaded Pd and Ni monometallic and PdNi bimetallic catalysts was studied in liquid phase at mild conditions. XPS results suggest that nickel addition to Pd modifies the electronic state of palladium as nickel loading is increased. Low-loaded Pd catalysts showed the highest selectivities (> 95%). The most active prepared catalyst, PdNi(1%), was more selective than the Lindlar catalyst.

Synchronous scanning phosphorimetry for the selective determination of chrysene: a metrological study

Room-temperature phosphorimetry was used to quantify trace levels of chrysene in sugar-cane spirits and in fish bile. A selective phosphorescence enhancer (AgNO3) and synchronous scanning allowed the detection of ng amounts of chrysene. Accuracy (113 ± 17%) and selectivity was evaluated using the CRM-NIST-1647d - Priority Pollutant Polycyclic Aromatic Hydrocarbons in acetonitrile. Analysis of sugar-cane spirit samples enabled recovery of 108 ± 18% which agreed with the one achieved using HPLC. Method's uncertainty was equivalent to 3.4 ng of the analyte, however, the analyte pre-concentration (SPE) improved sensibility and minimized the relative uncertainty. Characterization and homogeneity studies in fish bile were also performed.

Selective and non-extractive spectrophotometric determination of cefdinir in formulations based on donor-acceptor complex formation

Cefdinir has broad spectrum of activity and high prescription rates, hence its counterfeiting seems imminent. We have proposed a simple, fast, selective and non-extractive spectrophotometric method for the content assay of cefdinir in formulations. The method is based on complexation of cefdinir and Fe under reducing condition in a buffered medium (pH 11) to form a magenta colored donor-acceptor complex (λ max = 550 nm; apparent molar absorptivity = 3720 L mol-1 cm-1). No other cephalosporins, penicillins and common excipients interfere under the test conditions. The Beer's law is followed in the concentration range 8-160 µg mL-1.

Extraction and isolation of dictamnine, obacunone and fraxinellone from Dictamnus dasycarpus Turcz. by supercritical fluid extraction and high-speed counter-current chromatography

Supercritical fluid extraction was used to extract active compounds from the Chinese traditional medicinal D. dasycarpus under the pressure of 30 MPa and temperature of 45 ºC. Further separation and purification was established by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:0.8:1.3:0.9, volume ratio). The separation yielded a total of 47 mg of dictamnine, 24 mg of obacunone and 83 mg of fraxinellone from 1.0 g of the crude extract in one step separation with the purity of 99.2, 98.4 and 99.0%, respectively, as determined by HPLC. The chemical structures of these compounds were identified by ESI-MS, IR, ¹H-NMR and 13C-NMR.

Isolation and quantitative HPLC-PDA analysis of lupeol in phytopharmaceutical intermediate products from Vernonanthura ferruginea (Less.) H. Rob.

Prior to obtain a standardized dried extract from V. ferruginea, lupeol was first time isolated from leaves and used as chemical maker. An analytical method using HPLC-PDA for lupeol determination in V. ferruginea intermediate products was developed using a C8 reverse-phase column, acetonitrile-acetic acid (99.99:0.01, v/v) as mobile phase at 0.8 mL min-1, oven temperature at 23-25 ºC, sample injection volume at 30 µL and detection at 210 nm. The method presented linearity from 10 to 160 µg mL-1, accuracy, precision, robustness and suitable sensitivity proving to be a useful tool to the obtainment process of lupeol standardized dried extracts of V. ferruginea.

Phytotoxic effects of metabolites from Alternaria euphorbiicola against its host plant Euphorbia heterophylla

A bioassay-guided fractionation of culture filtrates of the fungus Alternaria euphorbiicola, a pathogen of the weed Euphorbia heterophylla, led to the isolation of anhydromevalonolactone (1), tyrosol (2), (R)-( - )-mevalonolactone (3), and cycloglycylproline (4). When tested on the punctured leaves of the host plant, these compounds produced bleached lesions with dark brown margins at concentrations as low as 80 µM. When tested on the leaves of other relevant weeds, only cycloglycylproline showed selective activity against E. heterophylla. This is the first report on the isolation of phytotoxins from A. euphorbiicola and on the phytotoxicity of anhydromevalonolactone, (R)-( - )-mevalonolactone, and cycloglycylproline.

Isolation and antitrichomonal activity of the chemical constituents of the leaves of Maytenus phyllanthoides Benth. (Celastraceae)

Cyclolignan (+)-lyoniresinol (1), veratric acid (2), vanillic acid (3), lupeol, oleanolic acid, 3β-hydroxy-urs-11-en-28,13β-lactone (4), the mixture of α- and β-amyrin, trans-polyisoprene, and β-sitosterol were isolated from the leaves of Maytenus phyllanthoides. The structures of the isolated compounds were established based on spectroscopic data, mainly ¹H and 13C nuclear magnetic resonance (NMR). Compound 1, its acetate analog 1a, and compounds 2, 3, and 4 were tested against Trichomonas vaginalis. (+)-Lyoniresinol showed activity corresponding to IC50 17.57 µM. This is the first report on the occurrence of 3β-hydroxy-urs-11-en-28,13β-lactone (4) in the Celastraceous family and lyoniresinol in the Maytenus genus, and on the antitrichomonal activity of lyoniresinol.

Selective detection of fluoride based on a pyridinium n-phenolate-calix[4]pyrrole displacement assay: an undergraduate laboratory experiment

A two-step experiment is proposed for a third year class in experimental organic chemistry. Over a period of five weeks, the students synthesized calix[4]pyrrole, a receptor that is highly selective for fluoride, and a pyridinium N-phenolate dye. Subsequently, the students used the synthesized compounds to investigate a displacement assay on the basis of the competition in acetonitrile between fluoride and the dye for calix[4]pyrrole. The experiment increased the students' skills in organic synthesis and in the characterization of organic compounds, provided a very attractive and accessible illustration of important supramolecular phenomena, and allowed the study of a chromogenic chemosensor.

ISOLATION AND CHARACTERIZATION OF NANOFIBRILLATED CELLULOSE FROM OAT HULLS

The objectives of this work were to investigate the microstructure, crystallinity and thermal stability of nanofibrillated cellulose obtained from oat hulls using bleaching and acid hydrolysis at a mild temperature (45 ºC) followed by ultrasonication. The oat hulls were bleached with peracetic acid, and after bleaching, the compact structure around the cellulosic fibers was removed, and the bundles became individualized. The extraction time (30 or 60 min) did not affect the properties of the nanofibrillated cellulose, which presented a higher crystallinity index and thermal stability than the raw material (oat hulls). The nanocellulose formed interconnected webs of tiny fibers with diameters of 70-100 nm and lengths of several micrometers, producing nanofibers with a relatively high aspect ratio, thus indicating that these materials are suitable for polymer reinforcement.