Modulation of imprinting efficiency in nanogels with catalytic activity in the Kemp elimination.

The interactions between the template and the functional monomer are a key to the formation of cavities in the imprinted nanogels with high molecular recognition properties. Nanogels with enzyme-like activity for the Kemp elimination have been synthesized using 4-vinylpyridine as the functional monomer and indole as the template. The weak hydrogen bond interaction in the complex is shown to be able to induce very distinctive features in the cavities of the imprinted nanogels. The percentage of initiator used in the polymerisation, ranging from 1% to 3%, although it does not have a substantial effect on the catalytic rate, reduces considerably the imprinting efficiency. The alteration of the template/monomer ratio is also investigated, and the data show that there is considerable loss of imprinting efficiency. In terms of substrate selectivity, a number of experiments have been performed using 5-Cl-benzisoxazole as substrate analogue, as well as 5-nitro-indole as template analogue for the preparation of a different set of nanogels. All the kinetic data demonstrate that the chemical structure of the template is key to the molecular recognition properties of the imprinted nanogels that are closely tailored and able to differentiate among small structural changes.