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

This study reports measurements of density, viscosity, and ternary mutual diffusion coefficients (D₁₁, D₁₂, D₂₁, D₂₂) 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 B coefficients. Apparent molar volumes (V_ϕ) were derived from the measured densities (ρ) for SMX and TMP in aqueous media. Furthermore, partial molar volumes of transfer at infinite dilution, ΔV_ϕ⁰, were evaluated to elucidate solute–solvent interactions within the ternary systems investigated. Nonzero ΔV_ϕ⁰ values, positive viscosity B coefficients, and negative cross-diffusion coefficients (D₁₂ and D₂₁), evidencing significant coupled diffusion, collectively indicate strong interactions between the antibiotics and cyclodextrins, consistent with host–guest complex formation.