In vivo 212Pb/212Bi generator using indium-DTPA-tagged liposomes

International audienceIndium-DTPA-tagged liposomes were studied in the present work as carriers of in vivo 212Pb / 212Bi generator to be used in targeted alpha therapy. The liposomal uptake of 212Pb, into preformed liposomes, was investigated using different lipophilic chelate (DCP, 2,3-dimercapto-1-propanol (BAL), sodium acetate, and A23187), as a function of various parameters (temperature, concentrations of lipids, Pb, DTPA,...) with 212Pb as a tracer. Different formulations of liposomes were tested to evaluate the radiolabeling efficiency. No complexing agent was necessary for the passage of Pb2+ through the membrane. It occurs naturally via a partial permeability of the lipid bilayer which increases with the temperature. A complexing agent (DTPA) appears necessary to concentrate Pb in the internal compartment of the liposomes. Conditions were found (T = 65°C, internal DTPA concentration of 0.025 M, pH 7.4, ...) yielding a high and rapid uptake of 212Pb in liposomes. The protocol established provides a novel method for the efficient entrapment of about 2-3 Pb atoms per liposome with a yield of 75% in conditions relevant for nuclear medicine

3D front face fluorescence spectroscopy as a tool for monitoring the oxidation level of edible vegetable oil during storage at 60 °C

International audienc

Front Face Fluorescence Spectroscopy Combined with PLS‐DA Allows to Monitor Chemical Changes of Edible Vegetable Oils during Storage at 60 °C

International audienc

Protocoles analytiques pour l'étude de la vanilline par RMN 13C isotopique en abondance naturelle (reproductibilté méthodologique, purification, origines du fractionnement isotopique)

La nouvelle méthodologie RMN 13C pour mesurer les teneurs en 13C site par site en abondance naturelle a permis d'envisager l'étude des mécanismes de biotransformation de l'acide férulique en vanilline. Dans un premier temps, il a fallu montrer que la RMN 13C donnait accès à des données fiables. Une étude de reproductibilité interne a été entreprise, ce qui a contribué à l'identification des points les plus sensibles de la méthode. Puis durant l'investigation des méthodes de purification des molécules sondes, des fractionnements isotopiques 13C normaux et inverses, ont été observés durant la chromatographie sur phase normale. Cette étude participe à la compréhension des effets isotopiques non-covalents. Un protocole analytique, permettant de limiter l'impact du fractionnement isotopique a été proposé. Enfin, la détermination de la filiation isotopique entre le substrat acide férulique et le produit vanilline a mis en évidence que l'intermédiaire "hydroquinone" est vraisemblablement l'étape commune aux deux micro-organismes étudiés (Streptomyces setonii et Amycolatopsis sp.). Une modélisation par calculs d'énergie appuie les données 13C obtenus. Une double perspective du travail de thèse est envisagée: (i) les effets isotopiques non-covalents étudiés par RMN 13C peuvent se transposer, par exemple, à l'étude de l'interaction entre des polluants et des sols contaminés, (ii) une méthodologie générale basée sur la RMN 13C isotopique peut devenir la technique de référence pour caractériser le statut naturel de la vanillineIsotopic 13C NMR can measure the site by site isotopic deviation in 13C, making it possible to study the mechanism of the biotransformation of ferulic acid to vanillin. A priori, it was necessary to developed conditions for the reliable measurement of very small deviations with sufficient precision. Hence, it was show that, during the purification of vanillin and ferulic acid by silica gel column chromatography, unexpected site-specific isotopic deviation was introduced in different fractions recovered from the eluting peak. Both normal and inverse effects occurred, indicating that each isotopomers has a characteristic elution profile due to specific interactions with the stationary/mobile phases used. Thus, insights into the causes of non-covalent isotopic fractionation in chromatography have been obtained. The technique was applied to the biotransformation of ferulic acid to vanillin by micro-organisms, Streptomyces setonii and Amycolatopsis sp. These experiments provided clear evidence supporting the prior hypothesis of a role of a hydroquinone intermediate in the C6C3 to C6C1 chain-shortening mechanism. This conclusion was supported by theoretical calculations of the predicted isotope effects. Future developments will include studies of the role of non-covalent interactions in isotopic fractionation, notably within the context of interactions between pollutants and contaminated soils, and the development of a general method for the authentication of the origin of natural vanillin through the analysis of the site-by-site deviations in 13C determined by 13C NMRNANTES-BU Sciences (441092104) / SudocSudocFranceF

Impact of storage period and lipid unsaturation on the kinetic of 5-hydroxymethylfurfural and furfural generation in pound cakes

International audienc

Nuclear Magnetic Resonance, Thermogravimetric and Differential Scanning Calorimetry for Monitoring Changes of Sponge Cakes During Storage at 20 °C and 65 % Relative Humidity

This paper presents a study on sponge cakes produced at the pilot scale and monitored during ageing (i.e. 1, 3, 6, 9, 16 and 20 day(s)) by different analytical techniques: nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results from NMR showed that the spin–lattice relaxation time (T1), measured on the crumb part, decreased from day 1 to day 16 while the spin–spin relaxation time (T2) increased throughout the whole storage time (i.e. 1 to 20 day(s)). Based on the analysis of the state of water, TGA allowed to establishing a kinetic profile of retrogradation degree of starch contained in sponge cakes. This approach evidenced that the evolution of the sponge cakes freshness and staling closely depends on the dynamic of the water in the crumb during ageing. These results were supported by DSC thermograms exhibiting a variation of three main endotherms detected in sponge cakes at −15, +5 and +45 °C throughout ageing. The enthalpy changes of these endotherms reflected the evolution of chemical and physical reactions occurring in the sponge cakes during storage. The analysis of the endotherm enthalpy change at 45 °C allowed to determine the time τ (i.e. τ≈9 days) corresponding to the apparition of amylopectin crystallites that could be considered as a reference time to separate fresh sponge cakes from the aged ones

Potentiality of front-face fluorescence and mid-infrared spectroscopies coupled with partial least square regression to predict lipid oxidation in pound cakes during storage

International audienc

Mid infrared as a tool to study the conformational structure of starch and proteins with oil addition during gelatinization

International audienc

Development of 2D and 3D front face fluorescence spectroscopy for monitoring ultrasound treatment in the removal of pesticides residues from fresh lettuces at the laboratory and pilot scales

International audienc