Physico-chemical characterization of flavonol molecularly imprinted polymers (original) (raw)
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Molecules, 2010
Quantum chemical calculations were performed to characterize the interaction of the flavonol molecule (FL) with methacrylic acid (MAA) and 4-vinylpyridine (4VPy) in the formation of imprinted polymers. The polarizable continuum model (PCM) was used to gain insight on the type of interaction between the reactant molecules under vacuum conditions and in the presence of different solvents. The effect of solvent on the prepolymerization complex formation was evaluated through the stability energy, in which chloroform behaves as the best solvent for the synthesis of the imprinted polymers since it facilitates the reaction by lowering its degree of stabilization. The reactivity was analyzed in terms of the electrostatic surface potential (ESP) and Mulliken charge. By means of these results, it has been possible to determine two potential recognition sites for the interaction of the MAA monomer and one for the 4VPy in relation to the strength of interaction with FL. In this concern, the interaction of the system FL-MAA is stronger than FL-4VPy.
New Methods to Study the Behavior of Molecularly Imprinted Polymers in Aprotic Solvents
Polymers, 2018
This work presents three new experimental methods for studying molecular imprinting. The electric conductivity measurements of the pre-polymerization mixture of amine templates in an aprotic solvent provide evidence of ionic dissociation of the pre-polymerization complexes. The displacement measurement of the template propranolol from its molecularly imprinted polymer (MIP) using a quaternary ammonium ion in toluene, shows that this MIP behaves as an ion exchanger even in a non-polar solvent. The same experiment also shows that template binding to the MIP from toluene involves ionic interaction. The third experimental method introduced here serves to study the models of template binding on MIPs. To this end the binding isotherm of propranolol (PR) has been measured on a polymer mixture consisting of non-imprinted control polymer (NIP) and a stronger binding acidic polymer, respectively. All three methods are suitable for studying several other imprinting systems.
Methacrylic Acid (MAA) based Molecularly Imprinted Polymer (MIP) is potentially used as an active material for biosensor. MIP is prepared to contain cavities that are leaved by template molecules. In the next time, target molecules that have a similar physical structure and properties with that of target molecules, can be trapped in the cavities. The main mechanism of the target recognition is the similarity of the space structure of the cavities and target molecules, but the molecular interaction between MAA and target molecules is also important. In this study, the interaction between two MAA molecules and one D-Glucose molecule is investigated using the Density Functional Theory (DFT). In the calculation, the Gaussian 09 with B3LYP and 631+G(d) basis sets is used to calculate all the electronic properties. The presence of the interaction was observed through the changes of the distances between specified atoms of the two molecules. The result is in line with the previous experimental study on potentiometric measurement of MAA-based MIP sensor for D-glucose as target molecule.
Adsorption Science & Technology, 2012
The present work compares the molecular recognition abilities of two molecularly imprinted polymers (MIPs) synthesized using two different functional monomers, viz. acrylamide (AA) and 4-vinylpyridine (4-Vp), employing gallic acid (GA) as the template using the non-covalent imprinting approach employing ethylene glycol dimethacrylate (EGDMA) as the cross-linker and 2,2-azo-bis-2-isobutyronitrile (AIBN) as an initiator in the porogen acetonitrile by thermal polymerization. The change in the electronic stabilization energies (∆E) of the template-monomer complexes formed between the template and functional monomers in the presence of the porogen were computed using Density Functional Theory (DFT) to interpret the nature of the interactions between them and to compare their stabilities. A systematic investigation of the molecular recognition abilities of the synthesized MIPs has been carried out by applying the Langmuir-Freundlich (L-F) adsorption isotherm model. The binding parameters obtained from the L-F model demonstrate that MIP AA exhibited a higher specific molecular recognition ability towards the template molecule.
Journal of Chromatography B, 2004
Molecularly imprinted polymers (MIPs) are polymers that can be tailored with affinity and selectivity for a molecule of interest. Offsetting the low cost and ease of preparation of MIPs is the presence of binding sites that vary widely in affinity and selectivity. Presented is a review of methods that take into account binding site heterogeneity when calculating the binding properties of MIPs. These include the bi-Langmuir, Freundlich, and Langmuir-Freundlich binding models. These methods yield a measure of heterogeneity in the form of binding site affinity distributions and the heterogeneity index. Recent developments have made these methods surprisingly easy to use while also yielding more accurate measures of the binding properties of MIPs. These have allowed for easier comparison and optimization of MIPs. Heterogeneous binding models have also led to a better understanding of the imprinting process and of the advantages and limitations of MIPs in chromatographic and sensor applications.
Characterization of Molecularly Imprinted Polymers with the Langmuir−Freundlich Isotherm
Analytical Chemistry, 2001
A new method of characterizing molecularly imprinted polymers (MIPs) was developed and tested, which provides a more accurate means of identifying and measuring the molecular imprinting effect. In the new polar solvent titration method, a series of imprinted and non-imprinted polymers were prepared in solutions containing increasing concentrations of a polar solvent. The polar solvent additives systematically disrupted the templation and monomer aggregation processes in the prepolymerization solutions, and the extent of disruption was captured by the polymerization process. The changes in binding capacity within each series of polymers were measured, providing a quantitative assessment of the templation and monomer aggregation processes in the imprinted and nonimprinted polymers. The new method was tested using three different diphenyl phosphate imprinted polymers made using three different urea functional monomers. Each monomer had varying efficiencies of templation and monomer aggregation. The new MIP characterization method was found to have several advantages. To independently verify the new characterization method, the MIPs were also characterized using traditional binding isotherm analyses. The two methods appeared to give consistent conclusions. First, the polar solvent titration method is less susceptible to false positives in identifying the imprinting effect. Second, the method is able to differentiate and quantify changes in binding capacity, as measured at a fixed guest and polymer concentration, arising from templation or monomer aggregation processes in the prepolymerization solution. Third, the method was also easy to carry out, taking advantage of the ease of preparing MIPs.
Chromatographic characterization of molecularly imprinted polymers
Analytical and Bioanalytical Chemistry, 2008
Recent efforts in the investigation of chromatographic characterization of molecularly imprinted polymers (MIPs) have focused mainly on the nature of heterogeneous binding sites. More data on the thermodynamics than on the kinetic features of MIP columns have been published. The present article addresses the sources of peak broadening and tailing, which are the main drawbacks often associated with imprinted polymers in chromatography for practical applications. With use of the theory of nonlinear chromatography, the peak properties of a MIP column, including the retention and peak broadening and tailing, can be well interpreted. Efforts to improve chromatographic efficiency using MIPs prepared by approaches different from the conventional method, including covalent imprinting and the format of uniformly sized spherical microbeads, are reviewed and discussed. This review leads to the conclusion that nonlinear chromatography theory is useful for characterizing chromatographic features of MIP columns, since a MIP is essentially an affinity-based chromatographic stationary phase. We expect more theoretical and experimental studies on the kinetic aspects of MIP columns, especially the factors influencing the apparent rate constant, as well as the analysis of the influences of mobile-phase composition on the chromatographic performance. In addition to revealing the affinity interaction by molecular recognition, slow nonspecific interactions which may be inherited from the imperfect imprinting and may be involved in the rebinding of the template to MIPs also need to be characterized.
Sensors
The possibility of investigating the binding properties of the same molecularly imprinted polymer (MIP), most probably heterogeneous, at various concentration levels by different methods such as batch equilibration and sensing, is examined, considering two kinds of sensors, based respectively on electrochemical and surface plasmon resonance (SPR) transduction. As a proof of principle, the considered MIP was obtained by non-covalent molecular imprinting of 2-furaldehyde (2-FAL). It has been found that different concentration ranges of 2-FAL in aqueous matrices can be measured by the two sensing methods. The SPR sensor responds in a concentration range from 1 × 10−4 M down to about 1 × 10−7 M, while the electrochemical sensor from about 5 × 10−6 M up to about 9 × 10−3 M. The binding isotherms have been fit to the Langmuir adsorption model, in order to evaluate the association constant. Three kinds of sites with different affinity for 2-FAL have been detected. The sites at low affinity...
Molecularly Imprinted Polymers: Present and Future Prospective
International Journal of Molecular Sciences, 2011
Molecular Imprinting Technology (MIT) is a technique to design artificial receptors with a predetermined selectivity and specificity for a given analyte, which can be used as ideal materials in various application fields. Molecularly Imprinted Polymers (MIPs), the polymeric matrices obtained using the imprinting technology, are robust molecular recognition elements able to mimic natural recognition entities, such as antibodies and biological receptors, useful to separate and analyze complicated samples such as biological fluids and environmental samples. The scope of this review is to provide a general overview on MIPs field discussing first general aspects in MIP preparation and then dealing with various application aspects. This review aims to outline the molecularly imprinted process and present a summary of principal application fields of molecularly imprinted polymers, focusing on chemical sensing, separation science, drug delivery and catalysis. Some significant aspects about preparation and application of the molecular imprinting polymers with examples taken from the recent literature will be discussed. Theoretical and experimental parameters for MIPs design in terms of the interaction between template and polymer functionalities will be considered and synthesis methods for the improvement of MIP recognition properties will also be presented.
Biosensors and Bioelectronics, 2008
Molecularly imprinted polymers (MIPs) for zearalenone analysis have been synthesized using the template mimics cyclododecyl 2,4-dihydroxybenzoate (CDHB), resorcinol and resorcylic acid. The MIPs are photochemically prepared from 2-(diethylamino)ethyl methacrylate (2-DAEM), 4-vinylpyridine (VIPY), 2-hydroxyethyl methacrylate (HEMA) or 1-allylpiperazine (1-ALPP) as the functional monomers, trimethylolpropane trimethacrylate (TRIM) as cross-linker, azobis(isobutyronitrile) as initiator and acetonitrile as porogen. Non-imprinted polymers have been also synthesized for reference purposes. The textural properties of the novel polymers (BET areas, pore volumes and pore size distributions) have been determined from nitrogen adsorption-desorption isotherms. These parameters have shown to be strongly dependent on the presence of the template and the monomer nature. Scanning electron microscopy and solvent uptake experiments support these findings. Microporosity contributes less than 7% to the total pore volume for all the polymers prepared. Interestingly, a 3.5 nm pore opening is observed for all the polymers and additional pore apertures in the 20-40 nm region for VIPY-, HEMA-and 2-DAEM-based MIPs whereas a much wider opening size distribution has been measured for the 1-ALPP-based MIP. Molecular modeling and, particularly, 1 H NMR experiments demonstrate the strong (2:1) complex formed between 1-ALPP and the diphenolic CDHB (K 11 = 4.7 × 10 4 M −1 and K 12 = 2.6 × 10 2 M −1 in acetonitrile) that make the corresponding MIP the most suitable for zearalenone recognition in real samples.