Molecular imprinting of sol gel polymers for the detection of paraoxon in water

The molecular imprinting technique of the toxic organophosphate compound paraoxon was applied in thin films of organically modified silica (ORMOSIL) matrix. Paraoxon was imprinted in the ORMOSIL through pi-pi interaction and hydrogen or polar bonds originating from functional alkoxysilane monomers. The binding of paraoxon to the imprinted sol gel matrix was evaluated by inhibition of butyryl cholinesterase (BuChE) using the Ellman colorimetric assay. Two ORMOSILs that differ in the structure of the backbone monomer and functional monomers were investigated, and found to have similar specific binding properties. The kinetic profile of paraoxon binding to the polymer matrix was studied, and saturation was found to occur after ca. 2 h. The binding of paraoxon to the synthetic receptor was evaluated by application of the two site Langmuir analysis. Two classes of receptor sites were detected, with binding affinities of 0.04 and 7 nM, and site population of 57 and 25 nM, respectively.