A novel approach to the molecular imprinting of polychlorinated aromatic compounds

The aim of this investigation was to determine whether relatively weak inte ractions, such as hydrogen bonds to aromatic chlorine atoms and interaction s involving aromatic pi electrons could be exploited within artificial rece ptors, constructed using the technique of molecular imprinting. For the pur poses of this investigation we chose 2,3,7,8-tetrachlorodibenzodioxin (TCDD )as the model target. Imprinted polymers have been prepared with two new te mplates designed to create recognition sites for TCDD. The first of these, the bis-N-(4-vinylphenyl)urea derivative of 2,8-dichloro-3,7-diaminodibenzo dioxin, employed a carbonyl spacer to introduce aromatic amines into the po lymer after reductive cleavage of the template. The second, N-(2-(3,7,8-tri chlorodibenzodioxinyl))-2-methacryloyloxybenzamide, incorporated a salicyli c acid spacer and introduced a methacrylic acid residue into the polymer fo llowing hydrolysis. Both amine and acid groups were positioned in such a wa y as to interact with TCDD through the formation of weak hydrogen bonds to aromatic chlorine atoms. A second recognition element was introduced into t he binding sites by the inclusion of a polymerizable, electron-rich, aromat ic ether capable of forming pi-pi interactions with the electron-deficient dioxin molecule. Polymers imprinted with either template showed significant ly higher uptake of TCDD than the corresponding nonimprinted controls, even at concentrations as low as 2 nM.