154 research outputs found
Development of nano-encapsulation systems for the food antifungal natamycin: Formulation, characterization and post-processing
No full textFood spoilage has become in the last decades one of the biggest challenges faced by the food industry, with a significant amount of products thrown away at every step of the supply chain. Microbial contamination is listed as one of the major causes of food spoilage and can be at a large extent prevented by application of antimicrobial compounds. Recent trends on the market such as an increasing demand of consumers for natural preservatives and their application in reduced quantities, coupled with the difficulty for industrials to get new antimicrobials approved by health authorities, lead the food industry to a process of reformulation and improvement of functionality and efficiency of already approved ingredients. Natamycin, a naturally-occurring food preservative widely used for the protection of food surfaces, is one of the most popular antifungal agents currently used. This molecule presents several advantages linked to its natural origin, long history of safe use, efficiency at low concentrations and limited modification of food products when applied. Current formulations of the preservative offer however limited specificity or tunability towards applications and little possibilities of controlled/triggered release. This compound also presents a relatively poor aqueous solubility detrimental for its antifungal action and is very sensitive to early-stage degradation by environmental factors such as extreme pH, oxidation and UV exposure. The main goal of this PhD thesis was to determine if the incorporation of this molecule within nano-encapsulation systems could provide benefits for availability, tunability and degradation issues. As a first step, formulation, optimization and characterization of two model nano-encapsulation systems (biodegradable polymeric nanospheres and nano-liposomes) were performed and compared in terms of relative benefit for the encapsulation, delivery, antifungal performance and stability of the antimicrobial. Post-processing of the most promising nano-encapsulation systems in order to obtain commercial products was further evaluated by purification/concentration (tangential flow filtration) or by transformation into redispersible dry products by lyophilization.Nano-liposomes were found overall superior to polymeric nanospheres for the encapsulation and delivery of our molecule and offer higher possible levels of tunability in terms of release rates and antifungal performance. Lyophilization in presence of carbohydrates turned out to be a valuable method for the preparation of dried products with enhanced long-term stability of the antifungal, compared to concentrates prepared by tangential flow filtration, a tedious process that impacted negatively the stability of the preservative
Lanthanide(III) and actinide(III) complexes [M(BH4)2 (THF)5][BPh4] and [M(BH4)2(18-crown-6)][BPh4] (M = Nd, Ce, U): synthesis, crystal structure, and density functional theory investigation of the covalent contribution to metal-borohydride bonding.
No full textInternational audienceTreatment of [M(BH4)3(THF)3] with NEt3HBPh4 in THF afforded the cationic complexes [M(BH4)2(THF)5][BPh4] [M = U (1), Nd (2), Ce (3)] which were transformed into [M(BH4)2(18-crown-6)][BPh4] [M = U (4), Nd (5), Ce (6)] in the presence of 18-crown-6; [U(BH4)2(18-thiacrown-6)][BPh4] (7) was obtained from 1 and 18-thiacrown-6 in tetrahydro-thiophene. Compounds 1, 3.C4H8S, 4.THF, 5, and 6.THF exhibit a penta- or hexagonal bipyramidal crystal structure with the two terdentate borohydride ligands in apical positions; the BH4 groups in the crystals of 7.C4H8S are in relative cis positions, and the thiacrown-ether presents a saddle shape, with two diametrically opposite sulfur atoms bound to uranium in trans positions. The crystal structures of these complexes, as well as those of previously reported [M(BH4)2(THF)5]+ cations, do not reveal any clear-cut lanthanide(III)/actinide(III) differentiation. The structural data obtained for [M(BH4)2(18-crown-6)]+ (M = U, Ce) by relativistic density functional theory (DFT) calculations are indicative of a small shortening of the U...B with respect to the Ce...B distance, which is accompanied by a lengthening of the U-Hb bonds and an opening of the Hb-B-Hb angle (Hb = bridging hydrogen atom of the eta3-BH4 ligand). The Mulliken population analysis and the natural bond orbital analysis indicate that the BH4 -->M(III) donation is greater for M = U than for M = Ce, as well as the overlap population of the M-Hb bond, thus showing a better interaction between the uranium 5f orbitals and the Hb atoms. The more covalent character of the B-H-U three-center two-electron bond was confirmed by the molecular orbital (MO) analysis. Three MOs represent the pi bonding interactions between U(III) and the three Hb atoms with significant 6d and 5f orbital contributions. These MOs in the cerium(III) complex exhibit a much lesser metallic weight with practically no participation of the 4f orbitals
Lanthanide(III) and Actinide(III) Complexes [M(BH<sub>4</sub>)<sub>2</sub>(THF)<sub>5</sub>][BPh<sub>4</sub>] and [M(BH<sub>4</sub>)<sub>2</sub>(18-crown-6)][BPh<sub>4</sub>] (M = Nd, Ce, U): Synthesis, Crystal Structure, and Density Functional Theory Investigation of the Covalent Contribution to Metal-Borohydride Bonding
No full textTreatment of [M(BH4)3(THF)3] with NEt3HBPh4 in THF afforded the cationic complexes [M(BH4)2(THF)5][BPh4] [M = U (1), Nd (2), Ce (3)] which were transformed into [M(BH4)2(18-crown-6)][BPh4] [M = U (4), Nd (5), Ce (6)] in the presence of 18-crown-6; [U(BH4)2(18-thiacrown-6)][BPh4] (7) was obtained from 1 and 18-thiacrown-6 in tetrahydro-thiophene. Compounds 1, 3·C4H8S, 4·THF, 5, and 6·THF exhibit a penta- or hexagonal bipyramidal crystal structure with the two terdentate borohydride ligands in apical positions; the BH4 groups in the crystals of 7·C4H8S are in relative cis positions, and the thiacrown-ether presents a saddle shape, with two diametrically opposite sulfur atoms bound to uranium in trans positions. The crystal structures of these complexes, as well as those of previously reported [M(BH4)2(THF)5]+ cations, do not reveal any clear-cut lanthanide(III)/actinide(III) differentiation. The structural data obtained for [M(BH4)2(18-crown-6)]+ (M = U, Ce) by relativistic density functional theory (DFT) calculations are indicative of a small shortening of the U···B with respect to the Ce···B distance, which is accompanied by a lengthening of the U−Hb bonds and an opening of the Hb−B−Hb angle (Hb = bridging hydrogen atom of the η3-BH4 ligand). The Mulliken population analysis and the natural bond orbital analysis indicate that the BH4 → M(III) donation is greater for M = U than for M = Ce, as well as the overlap population of the M−Hb bond, thus showing a better interaction between the uranium 5f orbitals and the Hb atoms. The more covalent character of the B−H−U three-center two-electron bond was confirmed by the molecular orbital (MO) analysis. Three MOs represent the π bonding interactions between U(III) and the three Hb atoms with significant 6d and 5f orbital contributions. These MOs in the cerium(III) complex exhibit a much lesser metallic weight with practically no participation of the 4f orbitals
Effect of citrate additive on the electrodeposition and corrosion behaviour of Zn–Co alloy
No full textTHE INFLUENCE OF Β-PBO2 ON PZT PHASE FORMATION
No full textThe reactional mechanism of the formation of solid solution lead-zircono-titanate PZT has been studied using β-PbO2, TiO2 and ZrO2 as starting materials. PZT ceramics were prepared by solid state reaction between oxides at different temperatures. After calcination samples are characterized by thermogravimetry (TGA), differential thermal analysis (DTA), differential scanning, Infrared spectroscopy and x-ray diffraction (XRD). Using lead dioxide (β-PbO2) allows PZT powder to be sintered at a temperature as low as 700°C
Multifunctional polymeric nanoparticles prepared from O/W nano-emulsions by a low-energy method
No full textPeer reviewe
THE INFLUENCE OF Β-PBO2 ON PZT PHASE FORMATION
No full textThe reactional mechanism of the formation of solid solution lead-zircono-titanate PZT has been studied using β-PbO2, TiO2 and ZrO2 as starting materials. PZT ceramics were prepared by solid state reaction between oxides at different temperatures. After calcination samples are characterized by thermogravimetry (TGA), differential thermal analysis (DTA), differential scanning, Infrared spectroscopy and x-ray diffraction (XRD). Using lead dioxide (β-PbO2) allows PZT powder to be sintered at a temperature as low as 700°C
ChemInform Abstract: Tri‐ and Tetranuclear Palladium‐Cobalt Clusters Containing Bridging Ph2PCH2PPh2(dppm) Ligands. Crystal Structures of (Pd2Co2(μ3‐CO)2(CO)5(μ‐dppm)2) and (Pd2Co(μ3‐CO)2(CO)2(μ‐dppm)2) (PF6).
No full textAge and Sex as Risk Factors for Lung Cancer in Setif Region - Algeria: Fuzzy Inference Modeling
No full text- …
