The Potential of Chitosan-Based Composites for Adsorption of Diarrheic Shellfish Toxins.

Okadaic acid (OA) is one of the most potent marine biotoxins, causing diarrheal shellfish poisoning (DSP). The proliferation of microalgae that produce OA and its analogues is frequent, threatening human health and socioeconomic development. Several methods have been tested to remove this biotoxin from aquatic systems, yet none has proven enough efficacy to solve the problem. In this work, we synthesized and characterized low-cost composites and tested their efficacy for OA adsorption in saltwater. For the synthesis of the composites, the following starting materials were considered: chitosan of low and medium molecular weight (CH-LW and CH-MW, respectively), activated carbon (AC), and montmorillonite (MMT). Characterization by vibrational spectroscopy (FTIR), X-ray diffraction (XRD), and microscopy revealed differences in the mode of interaction of CH-LW and CH-MW with AC and MMT, suggesting that the interaction of CH-MW with MMT has mainly occurred on the surface of the clay particles and no sufficient intercalation of CH-MW into the MMT interlayers took place. Among the composites tested (CH-LW/AC, CH-MW/AC, CH-MW/AC/MMT, and CH-MW/MMT), CH-MW/MMT was the one that revealed lower OA adsorption efficiency, given the findings evidenced by the structural characterization. On the contrary, the CH-MW/AC composite revealed the highest average percentage of OA adsorption (53 ± 11%). Although preliminary, the results obtained in this work open up good perspectives for the use of this type of composite material as an adsorbent in the removal of OA from marine environments.

Microencapsulation of selenium by spray-drying as a tool to improve bioaccessibility in food matrix.

Se in the form of sodium selenite was microencapsulated by spray - drying and added to a food matrix (yogurt) to study the potential improvement of its bioaccessibility. Yogurt samples were also supplemented with Se in free salt form. Se-loaded microparticles were successfully prepared by spray-drying with production yields above 70%. The supplementation of yogurt with Se in the form of free sodium selenite had a low effect on improving the bioaccessibility of this micronutrient (1%). In turn, Se microencapsulation with mannitol or mannitol/gastro-resistant polymer (Eudragit®) had a strong impact on bioaccessibility results. After the gastric phase, Se bioaccessibility reached values of 21 and 40% for the microencapsulated formulations, respectively. This percentage rose to 55% at the end of intestinal phase, showing no differences between both formulations. Our results show the relevance of microencapsulation as an effective tool to improve the bioaccessibility of micronutrients when they are used in food supplementation.

Dielectric Properties and Spectral Characteristics of Photocatalytic Constant of TiO2 Nanoparticles Doped with Cobalt.

Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc-Co[(C2H5)2NCS2]3). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO2:Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO2:0.1Co) where cobalt atoms can be uniformly distributed across the TiO2 matrix before metallic clusters start to form. It was also shown that CoTiO3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 °C and that oxygen defect Ti-O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO2 for all nanopowdered samples.

Extraordinary mechanical performance in disentangled UHMWPE films processed by compression molding.

An approach to obtain disentangled ultra-high molecular weight polyethylene (UHMWPE) films is proposed using a common compression molding. For that, disentangled UHMWPE nascent powders from reactor are processed at temperatures lower than the main melting peak and at high pressure. Then, disentangled UHMWPE films obtained from homogeneous polymerization powders and from those that incorporate SBA-15 mesoporous silica can be easily achieved by this simple methodology. These disentangled UHMWPE based materials show very high crystallinity and, consequently, outstanding elastic modulus and hardness, both further increasing by presence of mesoporous SBA-15 in the hybrids.

Spray-dried fucoidan microparticles for pulmonary delivery of antitubercular drugs.

Pulmonary tuberculosis accounts for 80% of cases and the delivery of antitubercular drugs into the lungs allows targeting the infected organ and, possibly, reducing systemic drug toxicity. This work aimed at using fucoidan as matrix of inhalable microparticles that associate two first-line antitubercular drugs, for an application in pulmonary tuberculosis therapy. Fucoidan is composed of fucose and sulphated sugar residues, moieties described as being recognised by surface receptors of alveolar macrophages, which host mycobacteria. Inhalable fucoidan microparticles loaded with antitubercular drugs were successfully produced with high association efficiencies of either isoniazid (95%) or rifabutin (81%). The microparticles evidenced no cytotoxicity on lung epithelial cells (A549). However, rifabutin-loaded microparticles showed a certain degree of toxicity on macrophage-like cells (THP-1) at the highest tested concentration (1 mg/mL). Furthermore, microparticles showed favourable aerodynamic properties for deep lung delivery (MMAD 2.0-3.8 µm) and, thus, show potential for an application as inhalable tuberculosis therapy.

Impact of Biohybrid Magnetite Nanoparticles and Moroccan Propolis on Adherence of Methicillin Resistant Strains of Staphylococcus aureus.

Biofilm bacteria are more resistant to antibiotics than planktonic cells. Propolis possesses antimicrobial activity. Generally, nanoparticles containing heavy metals possess antimicrobial and antibiofilm properties. In this study, the ability of adherence of Methicillin Resistant Strains of Staphylococcus aureus (MRSA) to catheters treated with magnetite nanoparticles (MNPs), produced by three methods and functionalized with oleic acid and a hydro-alcoholic extract of propolis from Morocco, was evaluated. The chemical composition of propolis was established by gas chromatography mass spectrometry (GC-MS), and the fabricated nanostructures characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbauer spectroscopy and Fourrier transform infrared spectroscopy (FTIR). The capacity for impairing biofilm formation was dependent on the strain, as well as on the mode of production of MNPs. The co-precipitation method of MNPs fabrication using Fe(3+) and Na2SO3 solution and functionalized with oleic acid and propolis was the most effective in the impairment of adherence of all MRSA strains to catheters (p < 0.001). The adherence of the strain MRSA16 was also significantly lower (p < 0.001) when the catheters were treated with the hybrid MNPs with oleic acid produced by a hydrothermal method. The anti-MRSA observed can be attributed to the presence of benzyl caffeate, pinocembrin, galangin, and isocupressic acid in propolis extract, along with MNPs. However, for MRSA16, the impairment of its adherence on catheters may only be attributed to the hybrid MNPs with oleic acid, since very small amount, if any at all of propolis compounds were added to the MNPs.

Inhalable Antitubercular Therapy Mediated by Locust Bean Gum Microparticles.

Tuberculosis remains a major global health problem and alternative therapeutic approaches are needed. Considering the high prevalence of lung tuberculosis (80% of cases), the pulmonary delivery of antitubercular drugs in a carrier system capable of reaching the alveoli, being recognised and phagocytosed by alveolar macrophages (mycobacterium hosts), would be a significant improvement to current oral drug regimens. Locust bean gum (LBG) is a polysaccharide composed of galactose and mannose residues, which may favour specific recognition by macrophages and potentiate phagocytosis. LBG microparticles produced by spray-drying are reported herein for the first time, incorporating either isoniazid or rifabutin, first-line antitubercular drugs (association efficiencies >82%). Microparticles have adequate theoretical properties for deep lung delivery (aerodynamic diameters between 1.15 and 1.67 µm). The cytotoxic evaluation in lung epithelial cells (A549 cells) and macrophages (THP-1 cells) revealed a toxic effect from rifabutin-loaded microparticles at the highest concentrations, but we may consider that these were very high comparing with in vivo conditions. LBG microparticles further evidenced strong ability to be captured by macrophages (percentage of phagocytosis >94%). Overall, the obtained data indicated the potential of the proposed system for tuberculosis therapy.

Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts.

Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N'-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] () and [MoO2Cl2(DEO)] (). The molecular structures of and were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55 °C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo(-1) h(-1) could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes and were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity.

Green synthesis of covellite nanocrystals using biologically generated sulfide: potential for bioremediation systems.

This work describes the synthesis of CuS powders in high yield and via an environmentally friendly and straightforward process, under ambient conditions (temperature and pressure), by adding to aqueous copper (II) a nutrient solution containing biologically generated sulfide from sulfate-reducing bacteria (SRB). The powders obtained were composed of CuS (covellite) nanoparticles (NPs) exhibiting a spheroid morphology (<5 nm). The relevance of this method to obtain CuS supported solid substrates has been demonstrated by performing the synthesis in the presence of TiO2 and SiO2 submicron particles. We further extended the work carried out, which substantiates the potential of using biogenic sulfide for the production of covellite nanocrystals and composites, using the effluent of a bioremediation column. Hence, such process results in the synthesis of added value products obtained from metal rich effluents, such as metallurgical and industrial ones, or Acid Mine Drainage (AMD), when associated with bioremediation processes.

The infrared spectrum of solid L-alanine: influence of pH-induced structural changes.

The influence of the pH on the infrared spectrum of L-alanine has been analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The amino acid was precipitated from aqueous solutions and dried at 36.5 degrees C, in order to stabilize cationic L-alanine or alaninium [CH3CH(NH3(+))COOH] at pH 1, the zwitterionic form [CH3CH(NH3(+))COO(-)] at pH 6, and anionic L-alanine or alaninate [CH3CH(NH2)COO(-)] at pH 13. New insight on the specific inter and intramolecular interactions in the different forms of L-alanine was reached by a novel methodological approach: an infrared technique not used before to analyze solid amino acid samples (DRIFTS), in combination with a detailed analysis based on spectral deconvolution. The frequency ranges of interest include the carbonyl/carboxyl stretching and amine deformation modes and the OH/NH stretching modes. It was shown that intermolecular hydrogen bonds between the NH3(+) and COO(-) groups are predominant in the zwitterionic form, whereas in cationic L-alanine, H bonds between the COOH groups are responsible for the formation of dimers. In anionic L-alanine, only strong electrostatic interactions between the COO(-) groups and Na(+) ions are proposed, evidencing the relevant role of the counterion.