Structure of aggregates in diluted aqueous octyl glucoside/tetraethylene glycol monododecyl ether mixtures with different alkanols

A new automated system for the preparation of sclerosant foam: A study of the physical characteristics produced and the device settings required

OBJECTIVES

To determine the quality of sclerosant foam produced with an automated preparation system with multiple combinations of sclerosing agents, gases, and device settings.

METHODS

Single-use mixing capsules filled with air or O₂/CO₂ and polidocanol (0.25, 1, or 3%) or sodium tetradecyl sulfate (0.2 or 1%) were coupled to a customized magnetic stirrer. Stirring speed and time were adjusted between 1500 and 4000 r/min and 30 and 60 s, respectively, and characteristics of the foam produced were measured: half-life, bubble diameter, and gas-to-liquid ratio.

RESULTS

With optimized device settings, the following foam characteristics were obtained: half-life range, 1.4 ± 0.9 to 5.2 ± 0.6 min; bubble diameter, 84 ± 14 to 119 ± 6 µm; and gas-to-liquid ratio, 5:1-7:1. Sodium tetradecyl sulfate foam was quicker to form than polidocanol but faster to degrade. Foams with low sclerosant concentrations and O₂/CO₂ required higher speed and longer time.

CONCLUSIONS

Suitable foam characteristics could be obtained with all combinations of sclerosing agent, concentration, and gas.

Elucidation of Spatial Distribution of Hydrophobic Aromatic Compounds Encapsulated in Polymer Micelles by Anomalous Small-Angle X-ray Scattering

Spatial distribution of bromobenzene (BrBz) and 4-bromophenol (BrPh) as hydrophobic aromatic compounds incorporated in polymer micelles with vesicular structure consisting of poly(ethylene glycol)-b-poly(tert-butyl methacrylate) (PEG-b-PtBMA) in aqueous solution is investigated by anomalous small-angle X-ray scattering (ASAXS) analyses near Br K edge. Small-angle X-ray scattering (SAXS) intensities from PEG-b-PtBMA micelles containing BrBz and BrPh were decreased as the energy of incident X-ray approached to Br K edge corresponding to the energy dependence of anomalous scattering factor of Br. The analysis for the energy dependence of SAXS profiles from the PEG-b-PtBMA micelles containing BrBz revealed that BrBz molecules were located in hydrophobic layer of PEG-b-PtBMA micelles. On the contrary, it was found by ASAXS that BrPh existed not only in the hydrophobic layer but also in the shell layer. Since ASAXS analysis successfully accomplished to visualize the spatial distribution of hydrophobic molecules in polymer micelles, it should be expected to be a powerful tool for characterization of drug delivery vehicles.

Chiral Cyclobutane β-Amino Acid-Based Amphiphiles: Influence of Cis/Trans Stereochemistry on Solution Self-Aggregation and Recognition

Novel diastereomeric anionic amphiphiles based on the rigid cyclobutane β-amino acid scaffold have been synthesized and deeply investigated with the aim of generating new functional supramolecular architectures on the basis of the rational design of original amphiphilic molecules and the control of their self-assembly. The main interest has been focused on the effect that cis/trans stereochemistry exerts on their molecular organization and recognition. In diluted solutions, the relative stereochemistry mainly influences the headgroup solvation and anionic-charge stabilization, i.e., better stabilized in the cis diastereoisomer due to intramolecular hydrogen-bonding and/or charge-dipole interactions. This provokes differences in their physicochemical behavior (pKa, cmc, conductivity) as well as in the structural parameters of the spherical micelles formed. Although both diastereoisomers form fibers that evolve with time from the spherical micelles, they display markedly different morphology and kinetics of formation. In the lyotropic liquid crystal domain, the greatest differences are observed at the highest concentrations and can be ascribed to different hydrogen-bonding and molecular packing imposed by the stereochemical constraints. Remarkably, the spherical micelles of the two anionic surfactants show dramatically diverse enantioselection ability for bilirubin enantiomers. In addition, both the surfactants form heteroaggregates with bilirubin at submicellar concentrations but with a different expression of supramolecular chirality. This points out that the unlike relative configuration of the two surfactants influences their chiral recognition ability as well as the fashion in which chirality is expressed at the supramolecular level by controlling the molecular organization in both micellar aggregates and surfactant/bilirubin heteroaggregates. All these differential features can be appropriate and useful for the design and development of new soft materials with predictable and tunable properties and reveal the cyclobutane motif as a valuable scaffold for the preparation of new amphiphiles.