Study of surfactant cross-linking by click chemistry on a model water/oil interface.

In this study, we explored how chemical reactions of amphiphile compounds can be characterized and followed-up on model interfaces. A custom-made surfactant containing three alkyne sites was first adsorbed and characterized at a water/oil interface. These amphiphiles then underwent interfacial crosslinking by click chemistry upon the addition of a second reactive agent. The monolayer properties and dilatational elasticity, were compared before and after the polymerization. Using bulk phase exchange, the composition of the aqueous bulk phase was finely controlled and washed to specifically measure the interfacial effects of the entities adsorbed and trapped at the interface. In this study, we aim to emphasize an original experimental approach to follow complex phenomena occurring on model interfaces, and also show the potential of this method to characterize multifactorial processes.

Revisiting the Three Vanadium Sandwich-Type Polyoxometalates: Structures, Solution Behavior, and Redox Properties.

It is well known that the trivacant anions α-B-[XW9O33]9- react with vanadyl ions to give the sandwich-type polyoxometalates [(VIVO)3(XW9O33)2]12- with X = AsIII or SbIII. Nevertheless, the oxidized derivatives have been obtained selectively by electrochemical oxidation from the fully reduced derivatives [(VIVO)3(XW9O33)2]12- allowing full characterization both in solution using UV-vis and multinuclear (17O, 51V, and 183W) NMR spectroscopies and in the solid state by single-crystal X-ray diffraction. Structural analysis of the oxidized [(VVO)3(XW9O33)2]9- polyanions is consistent with the idealized D3h symmetry, while solution studies reveal a fair hydrolytic stability in a wide pH range from 0 to 6. Besides, the D3h polyanions either as reduced or oxidized forms [(VO)3(AsW9O33)2]9/12- have been identified as the thermodynamic product that results from the conversion of the C2v polyanion [(H2O)(VO)3(AsW9O33)2]9/12- through moderate heating. Conversely, the SbIII-containing derivative gives exclusively the D3h polyanion, probably either due to the extended lone pair of the trigonal SbIII heterogroup that prevents the formation of the C2v arrangement or the lability of the oxo-metalate bonds that favor chemical exchange. The electrochemical studies of sandwich-type polyoxometalates revealed that each {V═O} group gives rise to a one-electron transfer process. At last, the redox properties appear strongly altered in the 0.3-5 pH range, consistent with proton-coupled electron transfers.

The pH-Induced Specific Area Changes of Unsaturated Lipids Deposited onto a Bubble Interface.

In this work, we used an original experimental setup to examine the behavior of insoluble monolayers made with pH-sensitive lipids. Two kinds of unsaturated lipids were chosen: a cationic one (lipid 1) bearing an ammonium headgroup and an anionic one (lipid 2) terminated with an acidic phenol group. The lipids were deposited onto an air bubble interface maintained in an aqueous phase and, after stabilization, were subjected to a series of compressions performed at different pH values. These experiments disclosed a gradual increase in the specific area per molecule when lipids were neutralized. Imposing a pH variation at constant bubble volume also provided surface pressure profiles that confirmed this molecular behavior. As complementary characterization, dilatational rheology disclosed a phase transition from a purely elastic monophasic system to a viscoelastic two-phase system. We hypothesized that this unexpected increase in the specific area with lipid neutralization is related to the presence of unsaturations in each of the two branches of the hydrophobic tails that induce disorder, thereby increasing the molecular area at the interface. Application of the two-dimensional Volmer equation of state allowed the generation of quantitative values for the specific areas that showed variations with pH. It also allowed the determination of apparent pKa values, which are affected by both the electrostatic potential within the monolayer and the affinity of the lipid polar head for the aqueous phase.

Probiotic encapsulation technology: from microencapsulation to release into the gut.

Probiotic encapsulation technology (PET) has the potential to protect microorgansisms and to deliver them into the gut. Because of the promising preclinical and clinical results, probiotics have been incorporated into a range of products. However, there are still many challenges to overcome with respect to the microencapsulation process and the conditions prevailing in the gut. This paper reviews the methodological approach of probiotics encapsulation including biomaterials selection, choice of appropriate technology, in vitro release studies of encapsulated probiotics, and highlights the challenges to be overcome in this area.

Deficiency of alpha-tocopherol in seminal fluid as a probable factor in low fertility in Côte d'Ivoire.

To evaluate the level of alpha-Tocopherol in seminal fluid of patients with low fertility, forty subjects with low fertility (17 with asthenospermia and 32 with oligoasthenospermia) and 21 subjects with normal sperm parameters were recruited into this study for assessing their alpha-Tocopherol seminal fluid level. The mean level of alpha-Tocopherol in subjects with normal sperm profile was 0.62 micromol/l compared to those with pathological profile such as asthenospermia (0.29 micromol/l) and oligoasthenospermia (0.28 micromol/l). The determination of alpha-Tocopherol in human seminal fluid provides useful information concerning the exploration of low fertility in Cote d'Ivoire.