Antibiotic–Cyclodextrin Interactions: An Effective Strategy for the Encapsulation of Environmental Contaminants

This study reports measurements of density, viscosity, and ternary mutual diffusion coefficients (<i>D</i>₁₁, <i>D</i>₁₂, <i>D</i>₂₁, <i>D</i>₂₂) for aqueous solutions containing two antibiotics-sulfamethoxazole (SMX) or trimethoprim (TMP) (component 1)-in the presence of various cyclodextrins (α-CD, β-CD, and γ-CD) (component 2) at 298.15 K. The relative viscosity data were analyzed by fitting to a second-order Jones-Dole equation via a least-squares regression to obtain the viscosity <i>B</i> coefficients. Apparent molar volumes (<i>V_ϕ</i>) were derived from the measured densities (<i>ρ</i>) for SMX and TMP in aqueous media. Furthermore, partial molar volumes of transfer at infinite dilution, Δ<i>V_ϕ</i>⁰, were evaluated to elucidate solute-solvent interactions within the ternary systems investigated. Nonzero Δ<i>V_ϕ</i>⁰ values, positive viscosity <i>B</i> coefficients, and negative cross-diffusion coefficients (<i>D</i>₁₂ and <i>D</i>₂₁), evidencing significant coupled diffusion, collectively indicate strong interactions between the antibiotics and cyclodextrins, consistent with host-guest complex formation.