Combinatorial Design of a Sialic Acid-Imprinted Binding Site

Aberrant glycosylation has been proven to correlate with various diseases including cancer. An important alteration in cancer progression is an increased level of sialylation, making sialic acid one of the key constituents in tumor-specific glycans and an interesting biomarker for a diversity of cancer types. Developing molecularly imprinted polymers (MIPs) with high affinity toward sialic acids is an important task that can help in early cancer diagnosis. In this work, the glycospecific MIPs are produced using cooperative covalent/noncovalent imprinting. We report here on the fundamental investigation of this termolecular imprinting approach. This comprises studies of the relative contribution of orthogonally interacting functional monomers and their synergetic behavior and the choice of different counterions on the molecular recognition properties for the sialylated targets. Combining three functional monomers targeting different functionalities on the template led to enhanced imprinting factors (IFs) and selectivities. This apparent cooperative effect was supported by 1H NMR and fluorescence titrations of monomers with templates or template analogs. Moreover, highlighting the role of the template counterion use of tetrabutylammonium (TBA) salt of sialic acid resulted in better imprinting than that of sodium salts supported by both in solution interaction studies and in MIP rebinding experiments. The glycospecific MIPs display high affinity for sialylated targets, with an overall low binding of other nontarget saccharides.