Evaluation of the origins of the selectivity of polymers imprinted with a HIV protease inhibitor using infrared spectroscopy and high performance liquid chromatography.
ABSTRACT This work investigates the origins of enantioselectivity of polymers imprinted with the HIV protease inhibitor, Indinavir. For the preparation of imprints of the drug, the critical interactions between the functional monomer, methacrylic acid, and Indinavir were characterized by infrared (IR) spectroscopy to explore the optimum functional monomer concentration for the polymerization. It was shown that a polymer with high selectivity and minimum non-selective binding for Indinavir was obtained when prepared with enough functional monomer to hydrogen bond with all of the functional groups of the drug without using an excess of monomer. This observation is explained in terms of a balance that is achieved in the monomer-template equilibrium during the polymerization that yields a polymer with highly selective sites and minimal non-selective sites. This paper further demonstrates that IR spectroscopy can be a valuable tool in the design and syntheses of molecular imprinted polymers.
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ABSTRACT: The influence of solvent polarity on the nature and extent of non-covalent interactions responsible for BPA:4-Vinlypyridine complex formation has been investigated in the pre-polymerization mixture and correlated with polymer-ligand recognition. The combination of FTIR, 1H NMR and UVeVis spectroscopy has made possible the development of a more comprehensive understanding of pre-polymerization events at a molecular level, and how they govern the properties of subsequent polymerized MIPs. The MIP ATR characterization provides direct insight into the bonding within matrix-template system, confirming that monomer:template H-bonded complexes survived the polymerization process and the presence of two functional monomers in the binding sites. The polymer has shown an excellent affinity for BPA in aqueous solutions with poor recognition in organic solvents. Loss of affinity in organic solvents together with selectivity studies suggested that the binding mechanism depended critically on the conformation of the polymeric binding pockets, which when combined with H-bonding and weak electrostatic interactions allowed for selective recognitionMaterials Chemistry and Physics 01/2013; 141:461. · 2.07 Impact Factor
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ABSTRACT: A detailed investigation into the functional groups responsible for the formation of a noncovalent complex between 2-aminopyridine (template) and methacrylic acid (functional monomer) has been carried out using FTIR spectroscopy and confirmed by (1)H NMR spectroscopic data. The approach adopted to confirm the mechanism of interaction was the analysis of the template plus the structurally similar 2-methylaminopyridine and 2-dimethylaminopyridine. A 1:1 stoichiometry of complexation was determined by Job plot analysis following titration, with FTIR results complementing those of the (1)H NMR study. The strength of interaction between 2-aminopyridine and the functional monomer measured through band shifts by FTIR spectroscopy was compared with such interactions for the isomers 3- and 4-aminopyridine. This comparison identified a clear correlation between template pK(a), degree of interaction and subsequent nonspecific binding in the nonimprinted polymer. Using FTIR spectroscopy it was also possible to observe the effect of temperature on the prepolymerisation solution. IR spectra showed that lower temperatures led to more stabilized interactions of the hydrogen-bonded complex. The potential advantages of FTIR spectroscopy compared with (1)H NMR spectroscopy in studying prepolymerisation solutions have been identified.Analytical and Bioanalytical Chemistry 07/2008; 391(4):1229-36. · 3.66 Impact Factor
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ABSTRACT: Molecular imprinting, a technique that allows for preparation of adsorbents with sites tailored for recognition of a particular molecule, continues to grow because it holds promise for several areas including separations. A key fundamental aspect in forming a molecular imprinted polymer (MIP) is the ability to optimize the amount of functional monomer relative to template used for the polymerization. In this paper, isothermal titration calorimetry (ITC) was used to predict the optimum functional monomer concentration for preparing an MIP for the drug, cinchonidine. Calorimetric titrations of cinchonidine with the functional monomer, methacrylic acid, suggested that a methacrylic acid–cinchonidine hydrogen bonded complex of minimum energy exists for solutions of 4:1 mol/mol of the monomer relative to the template. When this ratio of functional monomer to template was utilized for the MIP synthesis, the resulting polymer displayed significantly better selectivity for cinchonidine than polymers prepared with lesser or greater amounts of methacrylic acid. This observation is explained in terms of a balance that was achieved in the monomer–template equilibrium during the polymerization. This balance maximizes the favorable hydrogen bonding interactions with the template during the polymerization that yields the selective sites, but minimizes the use of excess monomer, which leads to non‐selective sites on the polymer. The results within suggest that ITC can be a valuable tool in the syntheses of MIPs.Journal of Liquid Chromatography & Related Technologies 01/2005; 28(1):1-15. · 0.57 Impact Factor