Influence of functional and cross-linking monomers and the amount of template on the performance of molecularly imprinted polymers in binding assays

An evaluation of molecularly imprinted polymers has been performed using ra dioligand binding assays. The bronchodilator theophylline was chosen as a m odel analyte and template molecule. The effect of type and amount of functi onal and cross-linking monomers, as well as of different combinations of fu nctional and cross-linking monomers has been studied with respect to the yi eld of high-affinity binding sites and their dissociation constants. Copoly mers of trifluoromethyl acrylic acid with divinylbenzene yielded the highes t, and the combination of trifluoromethyl acrylic acid with ethylene glycol dimethacrylate the lowest binding capacities. Polymers can be imprinted wi th very small amounts of template molecule without jeopardising their affin ity and specificity. Although binding isotherms revealed a slight decrease in the absolute number of high-affinity sites in polymers prepared with low template concentrations, the relative yield in high-affinity sites increas ed. This extends the potential applicability of non-covalent molecular impr inting to template molecules which are expensive, not available in large qu antities, or poorly soluble. The degree of cross-linking also seems to play a less important role for the recognition properties of the polymer in bin ding assay applications. Even only 19% crosslinked polymers were still spec ific, which could for instance facilitate the preparation of thin polymer f ilms or membranes.