Chiral Nafion membranes prepared by strong electrostatic binding of multiply positively charged β-cyclodextrin derivatives for tryptophan racemic mixtures’ separation

Abstract

Three multiply positively charged β-cyclodextrin derivatives were prepared and ionically bound to a Nafion® 117 membrane. The derivatives differed only in the length of the linker, which connects the positively charged anchor to the cyclodextrin moiety. The resulting membranes exert preferential sorption of l-enantiomer of tryptophan from its racemic mixture (ee reaching 44 % for the medium linker length). The membrane follows the retarded transport mechanism. Using a fluorophore-tagged cyclodextrin modifier, we confirmed no leaching of the modifier from the membrane. Thus, we proved the potential of the approach of electrostatic binding of chiral selectors for the enantioseparation of chiral drugs.