Biomedical subjects

C Tondre

Publications and source records attributed to C Tondre.

11 recordsLinked to original sources

PubMed2002

Glucose encapsulation in catanionic vesicles and kinetic study of the entrapment/release processes in the sodium dodecyl benzene sulfonate/cetyltrimethylammonium tosylate/water system.

The sodium dodecyl benzene sulfonate (SDBS)/cetyltrimethyl-ammonium tosylate (CTAT)/water ternary system has previously been shown to give rise to the formation of vesicles for well-defined compositions requiring an excess of one of the surfactants over the other. Two types of vesicular systems can thus be obtained (named V(+) and V(-), depending on the nature of the excess surfactant, i.e., CTAT or SDBS, respectively). In addition, the pure ion-pair amphiphile (IPA) can be obtained after removing the counterions. These different systems (V(+), V(-), and IPA) were investigated in regards to their ability to susbtantially retain a hydrophilic probe such as glucose. The influence of the initial glucose and surfactant concentrations was studied, and dialysis experiments were conducted with a view to determine the kinetics of glucose entrapment and release by the vesicles and, thus, to assess the possibility of a long-term encapsulation. The results indicate that all the vesicular systems studied here are characterized by quite a high permeability of the amphiphilic bilayer. However, SDBS-rich (V(-)) and IPA vesicles proved to be less permeable than CTAT-rich (V(+)) vesicles.

Benzenesulfonates↗

PubMed2001

Properties of the amphiphilic films in mixed cationic/anionic vesicles: a comprehensive view from a literature analysis.

The so-called 'catanionic' vesicles are made from mixtures of cationic and anionic surfactants. They are attracting much interest because they form spontaneously and they can be obtained from a variety of surfactants, either commercially available or issued from original synthesis. A distinction can be made between the properties of simple surfactant mixtures and of ion pair amphiphiles (IPA), in which the counterions have been removed. We have drawn up in this paper, an inventory of the different vesicular systems which have been described in the literature, insisting on the specific features associated with these two categories of systems. We have collected here especially, information concerning the phase behaviors, the microscopic composition of the vesicular particles, their structural and size determinations, the dynamic aspects (including the micelle-vesicle transition), the theoretical predictions from thermodynamic models and the entrapment of probe molecules. We discuss the potential of catanionic vesicles as delivery systems and we show that a full understanding of their entrapment/release properties will call for much more experimental work with well defined protocols. We also point out some unsolved questions concerning the role of the excess surfactant in the stabilization of the particles and the conditions required to obtain a favourable curvature of the surfactant film.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

Ultrafiltration of Micellar Solutions in the Presence of Electrolytes

Micellar extraction coupled with ultrafiltration techniques represents a potentially attractive tool for the removal of different kinds of contaminants from waste waters. Even though most industrial streams to be treated contain large amounts of electrolytes, very little is known about the behavior of micellar solutions in ultrafiltration when large amounts of salts are present. This paper is concerned with an investigation of two cationic surfactants (cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)) and one anionic surfactant (sodium dodecylsulfate (SDS)) in the presence of several salts occurring in specific industrial processes (carbonates and hydrogenocarbonates, nitrites, nitrates). The ultrafiltration behavior of these systems, with individual salt concentrations up to 0.9 M, is studied from the viewpoint of the fluxes obtained, the amount of surfactant leakage and of the membrane "gel point." Two types of polymeric membranes with molecular weight cutoff of 10,000 Da are considered (cellulose and polysulfone), which show significantly different behaviors.

Journal Article↗

PubMed1996

On the Behavior of Micellar Solutions in Tangential Ultrafiltration Using Mineral Membranes

Tangential ultrafiltration associated with the technology of mineral membrane is expected to offer several advantages compared to stirred cell ultrafiltration (often used at the laboratory level): (i) easier operating and cleaning procedures; (ii) better resistance to corrosion; (iii) reduced concentration polarization effects. The behavior of surfactant micelles, which can be used as the extracting phase in such processes, has been given little attention so far. The present work was aimed at investigating the behavior of different kinds of surfactants from the viewpoints of the permeate flux and of the amount of surfactant passing through the membrane. We have used two types of zirconium-titanium oxide membranes with molecular weight cutoff of 10,000 or 15,000 Da. The influence of parameters such as applied pressure, retentate flow rate, added salt, and value of pH was taken into consideration. The results obtained with cetylpyridinium chloride (CPC, cationic), sodium dodecyl sulfate (SDS, anionic), and polyethylene glycol tert-octylphenyl ether (Triton X-100, nonionic) are discussed in terms of their possible interactions with (or adsorption onto) the membranes and their supporting material.

Journal Article↗

PubMed1984