Abstract
Molecularly imprinted thin layers were prepared in silica capillaries by using two different surface polymerization strategies, the first using 4,4′-azobis(4-cyanovaleric acid) as a surface-coupled radical initiator, and the second, S-carboxypropyl-S’-benzyltrithiocarbonate as a reversible addition-fragmentation chain transfer (RAFT) agent in combination with 2,2′-azobisisobutyronitrile as a free radical initiator. The ability to generate imprinted thin layers was tested on two different polymerization systems: (i) a 4-vinylpyridine/ethylene dimethacrylate (4VP-EDMA) in methanol-water solution with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as a template; and (ii) methacrylic acid/ethylene dimethacrylate (MAA-EDMA) in a chloroform solution with warfarin as the template molecule. The binding properties of the imprinted capillaries were studied and compared with those of the corresponding non-imprinted polymer coated capillaries by injecting the template molecule and by measuring its migration times relative to a neutral and non-retained marker. The role of running buffer hydrophobicity on recognition was investigated by studying the influence of varying buffer acetonitrile concentration. The 2,4,5-T-imprinted capillary showed molecular recognition based on a reversed phase mechanism, with a decrease of the template recognition in the presence of higher acetonitrile content; whereas warfarin-imprinted capillaries showed a bell-shaped trend upon varying the acetonitrile percentage, illustrating different mechanisms underlying imprinted polymer-ligand recognition. Importantly, the results demonstrated the validity of affinity capillary electrochromatography (CEC) to screen the binding properties of imprinted layers.
Highlights
IntroductionMolecular imprinting is a popular approach for the preparation of tailor-made polymer-based molecular recognition systems for a predetermined molecular target.As a consequence, molecularly-imprinted polymers (MIPs) have attracted significant attention in many application fields including solid-phase extraction, chemical sensing, drug delivery, and catalysis [1,2,3,4].Nowadays, in MIP technology, the most popular synthetic approach is still based on bulk free radical polymerization because of its compatibility with a wide range of monomers and templates, Polymers 2018, 10, 192; doi:10.3390/polym10020192 www.mdpi.com/journal/polymersPolymers 2018, 10, x FOR PEER REVIEW as well asNowadays, for the mild conditions required.approach is characterized by poor in reactionMIP technology, the most popular syntheticthis approach is still based on bulk free control of polymer morphology and by a high resistance to mass-transfer in the resulting polymers.radical polymerization because of its compatibility with a wide range of monomers and templates, In order to overcome these drawbacks, andrequired.to moveHowever, towardsthis more efficient formats withbycontrolled as well as for the mild reaction conditions approach is characterized poor control ofwith polymer morphology andarchitectures by a high resistance to mass-transfer in thethermodynamic resulting polymers.morphology, defined nano-scale and improved kinetic and binding drawbacks, and to have movebecome towards one moreofefficient formats controlled properties, more advanced synthetic strategies the main needswith [5,6,7].morphology, with attractive defined nano-scale andnanomaterial improved kinetic and thermodynamicAmong the most synthesisarchitectures techniques in design is the “grafting from”
2,4,5-T and warfarin were used as model templates to prepare imprinted thin layers grafted on the inner surface of 75 μm-silica capillaries (Figure 2)
The two grafting approaches were both used with two different pre-polymerization systems in order to study the binding behaviour of imprinted thin layers obtained in markedly different experimental conditions
Summary
Molecular imprinting is a popular approach for the preparation of tailor-made polymer-based molecular recognition systems for a predetermined molecular target.As a consequence, molecularly-imprinted polymers (MIPs) have attracted significant attention in many application fields including solid-phase extraction, chemical sensing, drug delivery, and catalysis [1,2,3,4].Nowadays, in MIP technology, the most popular synthetic approach is still based on bulk free radical polymerization because of its compatibility with a wide range of monomers and templates, Polymers 2018, 10, 192; doi:10.3390/polym10020192 www.mdpi.com/journal/polymersPolymers 2018, 10, x FOR PEER REVIEW as well asNowadays, for the mild conditions required.approach is characterized by poor in reactionMIP technology, the most popular syntheticthis approach is still based on bulk free control of polymer morphology and by a high resistance to mass-transfer in the resulting polymers.radical polymerization because of its compatibility with a wide range of monomers and templates, In order to overcome these drawbacks, andrequired.to moveHowever, towardsthis more efficient formats withbycontrolled as well as for the mild reaction conditions approach is characterized poor control ofwith polymer morphology andarchitectures by a high resistance to mass-transfer in thethermodynamic resulting polymers.morphology, defined nano-scale and improved kinetic and binding drawbacks, and to have movebecome towards one moreofefficient formats controlled properties, more advanced synthetic strategies the main needswith [5,6,7].morphology, with attractive defined nano-scale andnanomaterial improved kinetic and thermodynamicAmong the most synthesisarchitectures techniques in design is the “grafting from”. In MIP technology, the most popular synthetic approach is still based on bulk free radical polymerization because of its compatibility with a wide range of monomers and templates, Polymers 2018, 10, 192; doi:10.3390/polym10020192 www.mdpi.com/journal/polymers. MIP technology, the most popular syntheticthis approach is still based on bulk free control of polymer morphology and by a high resistance to mass-transfer in the resulting polymers. To moveHowever, towardsthis more efficient formats withbycontrolled as well as for the mild reaction conditions approach is characterized poor control ofwith polymer morphology andarchitectures by a high resistance to mass-transfer in thethermodynamic resulting polymers. Morphology, defined nano-scale and improved kinetic and binding drawbacks, and to have movebecome towards one moreofefficient formats controlled properties, more advanced synthetic strategies the main needswith [5,6,7].
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