Molecular Imprinting in Thin Films of Organic−Inorganic Hybrid Sol−Gel and Acrylic Polymers

The molecular imprinting technique was applied on a model compound, propranolol, using two polymeric systems, acrylic and hybrid organic−inorganic sol−gels. The polymers were applied as thin films on glass substrates. The preparation of thin films of imprinted acrylic polymers required the development of a new polymerization system. The binding properties of the two polymers toward propranolol were characterized by radioactive and fluorimetric assay procedures. The acrylic system was found to have high uptake toward propranolol, but this was accompanied by a high degree of nonspecific binding. The sol−gel system had lower uptake, but remarkably lower nonspecific binding (<10%). The K d of the sol−gel matrix to propranolol is 80 ± 6 nM, a value that is common in biological systems. The binding was found to be solvent sensitive with high affinity and specificity in aqueous solution, which was completely lost in organic solvents. The uptake kinetics of the acrylic polymer was significantly slower than the sol−gel polymer, reaching saturation after 10 h, relative to <1 h for the sol−gel polymer. Imprinting of the sol−gel film with enantiomerically pure (S)-propranolol resulted in its pronounced chiral recognition over the (R)-enantiomer.