Preparation of Molecularly Imprinted Polymers Using Photocross-linkable Polyphosphazene and Selective Rebinding of Amino Acids

A photocrosslinkable polyphosphazene was used for molecular imprinting. We synthesized polyphosphazene (3) having urea groups for complexation with N-carbobenzyloxyglycin (Z-Gly-OH, template) and chalcone groups for cross-linking reaction. As substituents, 4-hydroxychalcone (1) and N-(4-hydroxyphenyl)-N'-ethylurea (2) were prepared. Choloro groups of poly(dichlorophosphazene) were replaced by the sequential treatment with sodium salts of compounds I and 2, and trifluoroethanol. The template molecule was complexed with the urea groups on the polymer chains via hydrogen bonding. A thin polymer film was prepared by casting a solution of the complex of polymer 3 and the template in dimethylformamide on a quartz cell and irradiated with 365 nm UV light to yield a cross-linked film with a thickness of about 16 mu m. The template molecules in the film were removed by Soxhlet extraction with methanol/acetic acid. The control polymer film was prepared in the same manner for the preparation of the imprinted polymer film, except that the template and triethylamine were omitted. In the rebinding test, the imprinted film exhibited much higher recognition ability for the template than the control polymer. We also investigated the specific recognition ability of the imprinted polymer for the template and its structural analogues. The rebinding tests were conducted using Z-Glu-OH, Z-Asp((OBu)-Bu-t)-OH, and Z-Glu-OMe. The imprinted film showed higher specific recognition ability for the template and the lowest response for Z-Asp((OBu)-Bu-t)-OH.