One monomer molecularly imprinted polymers (OMNiMIPs) have enhanced binding and selectivity properties versus traditionally formulated ethylene glycol dimethacrylate (EGDMA)/methacrylic acid (MAA) imprinted polymers. Further comparison was investigated toward multi-analyte imprinting capability of these two imprinted materials. Two templates, (R)-(+)-1,1'-bi-2-naphthol and BOC-L-tyrosine were simultaneously imprinted in the polymers, and the enantioselectivity compared to polymers imprinted with one template at a time. The simultaneously imprinted OMNiMIP exhibited only 6.3 and 21.1% loss in enantioselectivity for (R)-(+)-1,1'-bi-2-naphthol and BOC-L-tyrosine respectively, versus the singly imprinted OMNiMIPs. For the EGDMA/MAA imprinted polymer, enantioselectivity was only found for (R)-(+)-1,1'-bi-2-naphthol, with 59.1% loss in enantioselectivity found for the multiple-template imprinted polymer versus the (R)-(+)-1,1'-bi-2-naphthol singly imprinted polymer. It was also shown that imprinting two templates simultaneously leads to better enantioselective performance than mixing the particles of singly imprinted polymers. For example, the enantioselectivity of the R enantiomer of 1,1'-bi-2-binapthol on the simultaneously imprinted OMNiMIP gave a separation factor (alpha) value of 4.4, while the mixed-particle column gave an alpha value of 2.6. In addition, it was found that mixing an imprinted polymer with a non-imprinted polymer resulted in complete loss of chromatographic enantioselectivity in all cases (except the one that still showed severe loss of selectivity). Collectively, the results illustrate that imprinting mixtures of templates simultaneously is the method of choice, especially for OMNiMIPs, for producing multi-analyte molecular recognition in imprinted polymers.
A single bi-functional monomer, N,O-bismethacryloyl ethanolamine (NOBE), was used in precipitation polymerization system to synthesize molecularly imprinted polymer (MIP) microspheres. Highly specific binding sites were obtained for N-terminal protected neuropeptides, Boc-Leu-enkephalin and Pyr-Leu-enkephalin. The use of NOBE allowed binding sites to be formed in polymer microspheres that are able to recognize target peptides through the consensus C-terminal sequence. The interesting molecular binding results suggest a new approach for peptide analysis combining in situ chemical modification with MIP recognition under non-aqueous conditions.
New monomers were synthesized and evaluated for their molecular imprinting performance by a recently discovered methodology referred to as one monomer molecularly imprinted polymers (OMNiMIPs). The structural design of the new monomers was based on a lead compound methacrylamidoethyl methacrylate (1) used for the synthesis of OMNiMIP1, and introduced alkyl groups of various sizes at the alpha-amino position of the lead compound. Enantioselectivity, determined by liquid chromatography, was used to compare the performance of the imprinted polymers. Methyl substitution provided crosslinker 5 (2-methacrylamidopropyl methacrylate), which upon imprint polymerization afforded OMNiMIP5 with approximately the same enantioselectivity (alpha = 3.8) as OMNiMP1 (alpha = 3.7) made with the lead compound (1). The other two monomers (6 and 7) with larger alkyl substitutions (isopropyl and sec-butyl respectively) resulted in OMNiMIPs with low selectivity values (alpha = 1.0 and 1.2 respectively). Last, a strong influence of diastereomeric complexes on OMNiMIP5 selectivity was determined, with L: /L: and D: /D: monomer/template pairs giving alpha values of 3.6-3.8, while L: /D: and D: /L: monomer/template pairs had alpha values of 2.3-2.4. There is no intrinsic enantioselectivity seen for the OMNiMIP5 control polymer made without template at all, giving an alpha value of 1.03.
Molecularly imprinted polymers (MIPs) are an important class of selective materials for molecular specific sensors and separations. Molecular imprinting using non-covalent interactions in aqueous conditions still remains a difficult challenge due to interruption of hydrogen-bonding or electrostatic interactions water. Newly developed crosslinking ionic liquids are demonstrated herein to overcome problems of synthesizing aqueous MIPs, adding to previous examples of ionic liquids used as monomers in non-aqueous conditions or used as MIP solvents. Vinylimidazole ionic liquid crosslinkers were synthesized and subsequently explored as matrix supports for fabrication of molecularly imprinted polymeric nanoGUMBOS (nanoparticles derived from a group of uniform materials based on organic salts). Each of the four crosslinkers incorporated a unique functional spacer between the vinylimidazole groups, and the performance of the corresponding molecularly imprinted polymers was evaluated using chiral recognition as the diagnostic. High uptake values for l-tryptophan were found in the 13-87μmol/g range; and chiral recognition was determined via binding ratios of l-tryptophan over d-tryptophan that ranged from 5:1 to 13:1 for polymers made using different crosslinkers. Not only are these materials good for chiral recognition, but the results highlight the utility of these materials for imprinting aqueous templates such as biological targets for theranostic agents.
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