Bisphenol A-recognition polymers prepared by covalent molecular imprinting

A specific recognition material for bisphenol A (BPA) was prepared by using a covalent imprinting technique. A chloroform solution containing bisphenol A dimethacrylate as a template, ethylene glycol dimethacrylate as a cross-linking agent and 2,2ʹ-azobis(isobutyronitrile) as an initiator was polymerized by UV initiation. When BPA was removed from the resulting polymer by hydrolysis of the ester bonds with aqueous sodium hydroxide, carboxylic acid residues were generated in the polymer. After the polymer was packed into a stainless steel column, retention factors of BPA and related compounds were measured. The imprinted polymer adsorbed BPA and structurally related compounds such as 4,4ʹ-dihydroxybenzophenone, bis(4-hydroxyphenyl)sulfone and 4,4ʹ-dihydroxybiphenyl. A typical association constant (Ka) was calculated to be 1.72×10^5 M^-1 by Scatchard analysis. Interestingly, 17(alpha)- and 17(beta)-estradiol were also bound to the imprinted polymer (Ka=1.68×10^15 M^-1), indicating that the polymer could be used as artificial receptors for screening the compounds having estrogenic action.