Recognition directed site-selective chemical modification of molecularly imprinted polymers

Demonstrated is the site-selective chemical modification (SSCM) of molecula rly imprinted polymers (MIPs). In this strategy, MIPs are selectively chemi cally modified to improve the ratio of high-affinity to low-affinity bindin g sites and therefore the overall binding characteristics of the material, This was accomplished by preferentially eliminating the low-affinity bindin g sites by esterification with diazomethane or phenyldiazomethane. Selectiv ity in the esterification reaction was achieved using a guest molecule as a n in situ protecting group that preferentially shields the high-affinity si tes and leaves the low-affinity sites exposed toward reaction. The correspo nding shifts in the populations of high- and low-affinity sites were quanti fied using affinity distribution analysis, which quantitatively measures th e heterogeneous distribution of binding sites in MIPs as number of binding sites (N) with respect to binding affinity (K). Using affinity distribution analysis, the SSCM strategy was shown to improve the percentage of high-af finity sites in a methacrylic acid (MAA)/ethylene glycol dimethaerylate (EG DMA) matrix, imprinted with ethyl adenine-9-acetate (EA9A) in acetonitrile. The effects of different solvents and concentrations of guest molecule on the SSCM also were examined. The greatest improvements due to SSCM were obs erved when carried out in the imprinting solvent (acetonitrile). The demons trated SSCM methodology is complementary to existing strategies for improvi ng MIPs and thus can be utilized in tandem to improve the binding character istics of MIPs.