Molecular insights into the selective interaction of endocrine-disrupting chemicals with poly(mannuronate) in aqueous...

Estrogens and other steroid hormones, also known as endocrine-disrupting chemicals (EDCs), are emerging contaminants in wastewater effluent due to human activities. Although these compounds play essential roles in medical treatments and modern agriculture, their release into the environment has raised concerns because of their potential ecological and health impacts. The selective removal of EDCs from aqueous environments is a challenge due to competition with water molecules for binding sites. This work presents a systematic computational investigation of the intermolecular interactions and phase equilibria of selected EDCs and water in the presence of poly(mannuronate), a principal component of the brown-algae-derived biopolymer alginate, with the key goal of informing the design of polysaccharide-based materials for water remediation. Atomistic molecular dynamics simulations were coupled with stochastic calculations and extended off-lattice Flory-Huggins theory to assess polymer flexibility, penetrant-polymer coordination numbers, binding energies, and binary phase equilibria. To complement thermodynamic analysis, quantum chemical calculations were performed on representative low-energy configurations. Results showed that both the quantity and spatial positioning of species bound to alginate can be tuned via the relative proportions of guluronate versus mannuronate blocks constituting the polymer, providing a pathway for optimizing binding selectivity. Frontier molecular orbital analysis revealed distinct donor-acceptor characteristics for mannuronate-EDC complexes compared to mannuronate-water systems. These variations result in lower Flory-Huggins interaction parameters and enhanced thermodynamic compatibility of EDCs with the polymer matrix, suggesting preferential association in aqueous environments. Overall, this study provides molecular-level insights into the rational design of materials for the selective removal of EDCs from water systems.