Use of molecularly imprinted polymers from a mixture of tetracycline and its degradation products to produce affinity membranes for the removal of tetracycline from water

The possibility of introducing multiple recognition in artificial receptors by imprinting polymers, using a mixture of tetracycline (TC) and its degradation products as templates, has been examined. The recognition ability of the resulting molecularly imprinted polymer (MIP), as evaluated by batch rebinding assay, was found to be group-specific to tetracyclines, while the single tetracycline imprinted polymer (MIP-2) prepared using TC free from degradation products as the print molecule showed considerably high selectivity for doxycycline (DC) and modest selectivity for TC and other TC derivatives, oxytetracycline (OTC) and chlortetracycline (CTC). Based on the recognition property of the multiple tetracycline imprinted polymer (MIP-1), the polymer was applied in affinity membrane extraction as a class-selective adsorption phase to remove tetracyclines residues from water. For this purpose, the ground MIP was incorporated in a plasticized poly(vinyl chloride)membrane by casting method. Affinity separation of the obtained membrane was evaluated for the extraction of tetracycline and its analogs (CTC, OTC or DC) in aqueous solutions by a dialysis method. The membrane exhibited significantly stronger extraction ability towards tetracycline and structurally related compounds than a blank membrane having a non-printed polymer (NIP) as the adsorption phase. The result of these membrane extraction studies also indicates that the drug saturating at the receptor sites of MIP (deposited in membrane) faster will also be released into the receptor chamber faster. These affinity membranes were able to extract tetracyclines from water at all pHs, the highest selectivity being shown at pH 7 of the feed solution, which gives the lowest flux of the drug. Moreover, presence of salt in the feed solution increases the release of tetracycline bound in membrane. The results of the present study show that imprinting simultaneous with TC and TC degradation products formed in situ as a mixture template generates the group selectivity towards tetracyclines for the polymeric material. High affinity to a class of tetracycline of the membrane fabricated with this receptor, together with its fast and simple MIP fabrication, provides good possibilities for its application in separation processes of tetracycline antibiotics, which often contaminate the aqueous environment. (C) 2004 Elsevier B.V. All rights reserved.