Pharmaceuticals are contaminants of emerging concern. They enter the aquatic environment and are subject to chemical processes that influence their transport and fate. Natural organic matter (NOM) and biological membranes can play a role in aquatic pollutant distribution and transformation. NOM consists of carbon-based molecules and a wide-range of chemical functionalities. Little is known about the specific interactions pharmaceuticals have with these organic and biological surfaces. A systematic investigation has been conducted to selectively elucidate the type and strength of interactions pharmaceuticals exhibit with hydrophobic (C60 fullerene coated colloids), zwitterionic phospholipids (model membrane), and -NH2 and -COOH functionalized (self-assembled monolayer) surfaces. Carbamazepine (CBZ), amlodipine (AMP), and additional commonly detected pharmaceuticals have been used as probe molecules in the nano- to micro-molar concentration range. The binding affinities of the emerging contaminants (ECs) were determined using UV-Vis separation technique and quartz crystal microbalance based gravimetric analysis. Surface pressure-area isotherms collected using a Langmuir trough provided information about the lipid-pharmaceutical interactions. Our results show that the pharmaceuticals studied exhibit physisorption to these surfaces with binding constants ranging in the order of 105 – 107. A major implication is that NOM can alter the distribution and thereby the fate of ECs. Moreover, it is revealed that pure electrostatic interaction does not dictate the binding affinity. Hydrogen bonding, pi-cation, pi-pi, and hydrophobic interactions are the driving forces responsible for EC-NOM interactions, with binding strength dependent on specific pharmaceutical and surface composition. Specific EC-NOM interactions, along with the influence of these contaminants on the stability of lipid membranes, will be elaborated in terms of Gibbs free energy of binding and membrane elasticity calculations.

Role of non-covalent interactions on the transport and fate of pharmaceutical contaminants in the aquatic environment

2019 Spring National Meeting

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