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

In this study, we have investigated the host-guest inclusion complexes between β-cyclodextrin (βCD), 2-hydroxypropyl-β-cyclodextrin (2-HPβCD), and mono-6-tosyl-β-cyclodextrin (TS-βCD) 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/βCD complexes at various mass fractions of βCDs 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-βCD (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.