Characterization of the Binding Properties of Molecularly Imprinted Polymers

Abstract

The defining characteristic of the binding sites of any particular molecularly imprinted material is heterogeneity: that is, they are not all identical. Nonetheless, it is useful to study their fundamental binding properties, and to obtain average properties. In particular, it has been instructive to compare the binding properties of imprinted and non-imprinted materials. This chapter begins by considering the origins of this site heterogeneity. Next, the properties of interest of imprinted binding sites are described in brief: affinity, selectivity, and kinetics. The binding/adsorption isotherm, the graph of concentration of analyte bound to a MIP versus concentration of free analyte at equilibrium, over a range of total concentrations, is described in some detail. Following this, the techniques for studying the imprinted sites are described (batch-binding assays, radioligand binding assays, zonal chromatography, frontal chromatography, calorimetry, and others). Thereafter, the parameters that influence affinity, selectivity and kinetics are discussed (solvent, modifiers of organic solvents, pH of aqueous solvents, temperature). Finally, mathematical attempts to fit the adsorption isotherms for imprinted materials, so as to obtain information about the range of binding affinities characterizing the imprinted sites, are summarized.

Molecularly imprinted polymers—A closer look at the control polymer used in determining the imprinting effect: A mini review

“…[29][30][31][32] Values greater than one for selectivity, indicate that the imprinted polymer is able to differentiate closely related compounds and therefore an imprinting effect has occurred making it selective to the analyte. 33 Relative selectivity indicates the magnitude of selectivity of the MIP in relation to the NIP, where values greater than one imply that the MIP is more selective to the analyte. 34 α = Q Analyte Q Analogue ð5Þ α = IF Analyte IF Analogue ð6Þ…”

“…However, chromatographic method is particularly limiting because of the nonhomogeneous binding sites and slow rebinding kinetics leading to peak broadening. 33,35…”

Isotherm charts for material selection and method development with molecularly imprinted polymers and other sorbents

“…There exist many characterization methods like porosity measurements, infrared spectroscopy, thermal analysis and others, but the most important feature to be measured is the adsorption isotherm of the MIP [20]. The isotherm tells how much of a given substance is bound (adsorbed) by the the MIP in such a way that the results might be transferred to other applications or even to slightly changed conditions.…”

Assessment of the imprinting efficiency of an imide with a “stoichiometric” pyridine‐based functional monomer in precipitation polymerisation

“…As earlier presented in Table , 64% and 77% of the TAU added in the feed formulation of chloroform and acetonitrile‐porogenated MIPs, respectively, were incorporated in the monolithic MIPs resulting in a 1:1 stoichiometric T:FM ratio, but only rebound 2.8% (4.1 ± 0.2 μmol/g) and 2.3% (3.6 ± 0.1 μmol/g) of it, respectively. These results suggest that most of the incorporated template was not converted to high fidelity imprints in bulk imprinting, with some possibly destroyed during grinding of the monoliths . Conversely, their respective NIPs also recorded comparable TAU binding of 2.4 ± 0.1 μmol/g (BP‐1:1‐C) and 1.8 ± 0.2 μmol/g (BP‐1:1‐A) giving imprinting factors of 1.7 and 2.0, respectively.…”