Oxoanion Imprinting Combining Cationic and Urea Binding Groups: A Potent Glyphosate Adsorber

Abstract

The use of polymerizable hosts in anion imprinting has led to powerful receptors with high oxyanion affinity and specificity in both aqueous and non-aqueous environments. As demonstrated in previous reports, a carefully tuned combination of orthogonally interacting binding groups, for example, positively charged and neutral hydrogen bonding monomers, allows receptors to be constructed for use in either organic or aqueous environments, in spite of the polymer being prepared in non-competitive solvent systems. We here report on a detailed experimental design of phenylphosphonic and benzoic acid-imprinted polymer libraries prepared using either urea- or thiourea-based host monomers in the presence or absence of cationic comonomers for charge-assisted anion recognition. A comparison of hydrophobic and hydrophilic crosslinking monomers allowed optimum conditions to be identified for oxyanion binding in non-aqueous, fully aqueous, or high-salt media. This showed that recognition improved with the water content for thiourea-based molecularly imprinted polymers (MIPs) based on hydrophobic EGDMA with an opposite behavior shown by the polymers prepared using the more hydrophilic crosslinker PETA. While the affinity of thiourea-based MIPs increased with the water content, the opposite was observed for the oxourea counterparts. Binding to the latter could however be enhanced by raising the pH or by the introduction of cationic amine- or Na + -complexing crown ether-based comonomers. Use of high-salt media as expected suppressed the amine-based charge assistance, whereas it enhanced the effect of the crown ether function. Use of the optimized receptors for removing the ubiquitous pesticide glyphosate from urine finally demonstrated their practical utility.

Towards molecularly imprinted polymers that respond to and capture phosphorylated tyrosine epitopes using fluorescent bis-urea and bis-imidazolium receptors

“…Prior to incorporating the functional dye fCL into the polymer network, its spectroscopic behaviour towards the template was reassessed considering the use of a bis-imidazolium-type co-cross-linker and chloroform as the solvent, different from our previous study, to achieve optimal binding between the two urea units and the anion. 20 The template used was the sequence Y-pY-G, which shares structural similarity with the ZAP70 epitope Y-Y-T, 36 and it was employed in its C-terminus protected form (Scheme 2a) to prevent competition with the phosphate anion for binding to the functional cross-linkers in the final MIP preparation. Additionally, the N-terminus was protected with a fluorenylmethyloxycarbonyl (Fmoc) group to enhance the solubility of the template in organic solvents.…”

“…S13 and Section S6 for more details, ESI. † MIP and NIP core-shell polymer@SiO 2 particles synthesis After preliminary experiments, fluorescent core-shell polymer@ SiO 2 MIP and NIP particles were synthesised for the detection of the Y-pY-G sequence, structurally similar to the ZAP70 epitope Y-Y-T. 30,36 The synthesis involved the use of the fluorescent cross-linker fCL, the template Fmoc-Y-pY-G-OMe-TBA, the structural cross-linker ethylene glycol dimethacrylate (EGDMA), the structural co-monomer methacrylamide (MAAm) and the functional cross-linker bIm-PF 6 (Scheme 2a).…”