Comparative chemical examination of inclusion complexes formed with ß-cyclodextrin derivatives and basic amino acids.

In this study, we have investigated the host-guest inclusion complexes between ß-cyclodextrin (ßCD), 2-hydroxypropyl-ß-cyclodextrin (2-HPßCD), and mono-6-tosyl-ß-cyclodextrin (TS-ßCD) excipients and two amino acids, such as L-arginine (L-Arg) and L-lysine (L-Lys). The formation of inclusion complexes was detected, and a comparative study was conducted at different pH, density, and viscosity. A physical mixture, comprising equal amount of amino acids was used to prepare the complex in a solid-state form. The experimental parameters, such as apparent molar volume, limiting apparent molar volume, partial molar volume were analyzed by measuring density at infinite dilution. The other quantities, such as dynamic viscosity, kinematic viscosity, relative viscosity, intrinsic viscosity, spatial viscosity, activation energy were determined for amino acid/ßCD complexes at various mass fractions of ßCDs and different temperatures. Finally, we found moderate (R2 > 0.5) and strong (R2 > 0.7) linear relationships (p-value < 0.0001) between the dynamic viscosity and the temperature: the temperature evaluation promotes the decrease in dynamic viscosity for amnio acid-ßCD (its derivatives) complexes. The results of this study emphasize important properties of analyzed complexes that can be utilized in the development of controlled drug delivery vectors.

Probing inclusion complexes of 2-hydroxypropyl-ß-cyclodextrin with mono-amino mono-carboxylic acids: physicochemical specification, characterization and molecular modeling.

Density (ρ), viscosity (η) and surface tension (γ) of three amino acids (valine, alanine, and glycine) have been measured at a different mass fraction (0.002 - 0.009) of aqueous hydroxypropyl-ß-cyclodextrin (HPßCD) mixtures and different temperatures (278.15 - 295.15 K). The formation of inclusion complexes has been analyzed via evaluating the amounts of apparent and limiting apparent molar volumes, limiting apparent molar expansibilities, activation energy, kinematic, relative, intrinsic, spatial, and dynamic viscosities. The surface tension studies indicated that the inclusion complexes have been formed with 1:1 stoichiometry and mediated by hydrophobic effects and electrostatic forces. Additionally, the ρ and η parameters were evaluated by molecular modeling experiments to provide more details on the mechanisms of the complexation.