Calorimetric Analysis of the Interaction of Endocrine-Disrupting Chemicals with Cyclodextrins

Abstract Endocrine-disrupting chemicals (EDCs) leach from consumer products, are persistent in the environment, and are implicated in adverse health outcomes. Commonly suspected to be xenoestrogens, binding and subsequent removal of EDCs such as bisphenol A (BPA), bisphenol S (BPS), parabens, nonylphenols, triclosan, and phthalates is important for both human and environmental health. Cyclodextrins (CDs) are known to bind estrogens and the EDCs bisphenol A and bisphenol S. We investigated the host–guest interactions of α-, β-, and γ- CDs with a range of suspected xenoestrogens via isothermal titration calorimetry (ITC) in aqueous solution and calculated binding stoichiometry, association constants, Gibbs free energy, enthalpy, and entropy for each EDC-CD pair. We found the strongest complexation between the suspected xenoestrogens and β-CD, with no significant interaction observed with any of the selected EDCs and α-CD and only two EDCs showing complexation with γ-CD. Those EDCs that exhibit higher binding may be more likely to adopt an estrogen-like conformation in aqueous solution, and we anticipate these data will provide information useful for future research in removing these harmful chemicals from the environment.