Transport Properties in Multicomponent Systems Containing Cyclodextrins and Nickel Ions.

In this work, we propose a comprehensive experimental study of the diffusion of nickel ions in combination with different cyclodextrins as carrier molecules for enhanced solubility and facilitated transport. For this, ternary mutual diffusion coefficients measured by Taylor dispersion method are reported for aqueous solutions containing nickel salts and different cyclodextrins (that is, α-CD, ß-CD, and γ-CD) at 298.15 K. A combination of Taylor dispersion and other methods, such as UV-vis spectroscopy, will be used to obtain complementary information on these systems. The determination of the physicochemical properties of these salts with CDs in aqueous solution provides information that allows us to understand solute-solvent interactions, and gives a significant contribution to understanding the mechanisms underlying diffusional transport in aqueous solutions, and, consequently, to mitigating the potential toxicity associated with these metal ions. For example, using mutual diffusion data, it is possible to estimate the number of moles of each ion transported per mole of the cyclodextrin driven by its own concentration gradient.

Supramolecular gels of poly-α-cyclodextrin and PEO-based copolymers for controlled drug release.

The aim of this work was to prepare syringeable supramolecular gels of α-cyclodextrin-polymer (poly-αCD) with various poly(ethylene oxide) (PEO)-based copolymers, which can be suitable to form depots for controlled drug release. A series of water-soluble poly-αCDs was synthesized from αCD by crosslinking with epichlorohydrin in alkaline medium. The chemical composition of the polymers was characterized by NMR (αCD content>53%) and the molecular weight was evaluated using static light scattering (SLS). Supramolecular assemblies occurred by mixing poly-αCD (20-40% w/v) with a PEO-based polymer (i.e., PEG, Pluronic® F127 or Tetronic® 908) (10-15% w/v). Phase separation was observed and the αCD content in each phase was determined by means of the phenol-sulfuric acid colorimetric method. Formation of poly-αCD/PEO-based polymer 3D-supramolecular complexes was confirmed by diffusion-ordered NMR spectroscopy (DOSY) and X-ray diffractometry. The supramolecular assemblies showed good cytocompatibility against SAOS-2 cells and in the HET-CAM test. The supramolecular gels were able to sustain the release of vancomycin for at least 5 days at 37 °C, more efficiently than dispersions of each polymer component in separate. These results open new possibilities in the design of novel controlled delivery systems for the treatment of bone infections.

Calculations of Diffusion Coefficients of Iron Salts in Aqueous Solutions at 298.15 K: A Useful Tool for the Knowledge of the Structure of these Systems.

Diffusion coefficients, thermodynamic and mobility factors of iron salts in aqueous solutions are estimated from Onsager-Fuoss model. The influence of the ion size parameter a, "mean distance of closest approach of ions", determined from different approaches, on the variation of diffusion coefficients with concentration, is also discussed. The aim of this work is to have a better understanding of the structure of these systems and of the thermodynamic behaviour of iron salts in aqueous media.