Molecular imprinting and solid phase extraction of flavonoid compounds

Development of Silica Nanoparticle Supported Imprinted Polymers for Selective Lysozyme Recognition

Protein imprinted MIPs show notable potential for applications in many analytical areas such as clinical analysis, medical diagnostics and environmental monitoring, but also in drug delivery scenarios. In this study, we present various modifications of two different synthesis routes to create imprinted core-shell particles serving as a synthetic recognition material for the protein hen egg white (HEW) lysozyme. HEW lysozyme is used as food additive E 1105 for preservation due to its antibacterial effects. For facilitating quality and regulatory control analysis in food matrices, it is necessary to apply suitable isolation methods as potentially provided by molecularly imprinted materials. The highest binding capacity achieved herein was 58.82 mg/g with imprinting factors ranging up to 2.74, rendering these materials exceptionally suitable for selectively isolating HEW lysozyme.

Evaluation indicators of Ruditapes philippinarum nutritional quality

To access the nutritional quality of the Ruditapes philippinarum, a comprehensive quality evaluation procedure is always important to be established. In this study, fifteen nutritional quality evaluation indicators of R. philippinarum from 7 months were analyzed, and the most important indicators were determined using a combination of multiple chemometric methods such as correlation analysis (CA), principal component analysis (PCA), and system cluster analysis (SCA). Significant differences in nutritional quality were observed across the 7 months, as per the ANOVA results (P < 0.05). The coefficient of variation values for the fifteen evaluation indicators for R. philippinarum across 7 months was 1.67-43.47%. The CA results revealed that some indicators were correlated to each other within a certain range. Four principal components with eigen-values > 1 were obtained with PCA, and a cumulative contribution of 92.11% was achieved. In addition, four essential quality indicators were extracted using SCA. Using these four indicators, a simple and efficient procedure can be applied for quality control in aquaculture.

Magnetic molecularly imprinted polymers doped with graphene oxide for the selective recognition and extraction of four flavonoids from Rhododendron species

Herein, a novel magnetic molecularly imprinted polymer doped with reticular graphene oxide (Fe₃O₄@SiO₂-GO@MIPs) was synthesized for the selective recognition and extraction of 4 flavonoids (farrerol, taxifolin, kaempferol, and hyperin) from Rhododendrons species. The Fe₃O₄@SiO₂-GO@MIPs with lamellar membranes showed outstanding adsorption capacity. The 3D cavities complementary to the "shape" of farrerol were "imprinted" on the polymer framework after removal of farrerol template. Competitive binding assays showed that the polymer has a higher selectivity for farrerol compared with other analogues and references. The Fe₃O₄@SiO₂-GO@MIPs as solid-phase extraction adsorbents combined with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) was used for selective determination of four flavonoids from Rhododendrons samples. The limits of detection (LOD) were 0.07, 0.08, 0.06, and 0.08 μg L^-1 for farrerol, taxifolin, kaempferol, and hyperin, respectively. These results suggest that the prepared Fe₃O₄@SiO₂-GO@MIPs have the potential applicability to extract, purify, and enrich flavonoids from herbs, supplements, and other natural products.

Personalized Medicine for Crops? Opportunities for the Application of Molecular Recognition in Agriculture

This perspective examines the detection of rhizosphere biomarkers, namely, root exudates and microbial metabolites, using molecular recognition elements, such as molecularly imprinted polymers, antibodies, and aptamers. Tracking these compounds in the rhizosphere could provide valuable insight into the status of the crop and soil in a highly localized way. The outlook and potential impact of the combination of molecular recognition and other innovations, such as nanotechnology and precision agriculture, and the comparison to advances in personalized medicine are considered.

Efficient prediction of suitable functional monomers for molecular imprintingvialocal density of states calculations

Computational screening of suitable functional monomersvialocal density of states calculations.

Synthesis of Quercetin-imprinted Polymer Spherical Particles with Improved Ability to Capture Quercetin Analogues

INTRODUCTION

Molecularly imprinted polymers (MIPs) are composed of specific cavities able to selectively recognise a template molecule. Used as chromatographic sorbents, MIPs may not trap related structures due to the high rigidity of their cross-linking.

OBJECTIVE

To improve the capture of quercetin analogues by modulating the synthesis strategy for a quercetin-imprinted polymer (Qu MIP).

METHODOLOGY

An additional comonomer bearing a short oligoethylene glycol (OEG) unit was used to prepare a Qu MIP that was compared to a traditional one formulated in a similar fashion, but without the OEG-comonomer. The Qu MIPs were prepared in bead form through fluorocarbon suspension polymerisation. After solid phase extraction (SPE) assessment of their imprinted cavities, the MIPs were evaluated by HPLC for their recognition properties towards quercetin and other polyphenols, including flavonoids, phenolic acids and curcumin. The Qu MIPs were finally SPE-tested on a white onion extract.

RESULTS

The incorporation of OEG units modulated the selectivity of the Qu MIP by improving the recognition of quercetin related structures (12-61% increase in the imprinting effect for distant analogues). It also allowed limiting or suppressing non-specific hydrophobic interactions (decrease of about 10% in the rate of quercetin retention on the non-imprinted polymer). The SPE application of the MIP to a white onion extract indicates its interest for the selective extraction of quercetin and its analogues.

CONCLUSION

The OEG-modified Qu MIP appears to be an attractive tool to discover new drug candidates from natural sources by extracting, amongst interfering compounds, structural analogues of quercetin. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis and characterization of molecularly imprinted polymer membrane for the removal of 2,4-dinitrophenol

Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo–second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol.

Extraction and isolation of phenolic compounds

Phenolic compounds constitute a major class of plant secondary metabolites that are widely distributed in the plant kingdom and show a large structural diversity. These compounds occur as aglycones or glycosides, as monomers or constituting highly polymerized structures, or as free or matrix-bound compounds. Furthermore, they are not uniformly distributed in the plant and their stability varies significantly. This greatly complicates their extraction and isolation processes, which means that a single standardized procedure cannot be recommended for all phenolics and/or plant materials; procedures have to be optimized depending on the nature of the sample and the target analytes, and also on the object of the study. In this chapter, the main techniques for sample preparation, and extraction and isolation of phenolic compounds have been reviewed-from classical solvent extraction procedures to more modern approaches, such as the use of molecularly imprinted polymers or counter-current chromatography.

Preparation of nano-sized Pb2+ imprinted polymer and its application as the chemical interface of an electrochemical sensor for toxic lead determination in different real samples

In this work, a new nano-structured ion imprinted polymer (IIP) was synthesized by copolymerization of methacrylic acid-Pb(2+) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Methacrylic acid acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. A carbon paste electrode modified with IIP-nanoparticles was used for fabrication of a Pb(2+) sensitive electrode. Differential pulse stripping voltammetry method was applied as the determination technique, after open circuit sorption of Pb(2+) on the electrode and its reduction to metallic form. The IIP modified electrode showed a considerably higher response, compared to the electrode embedded with non-imprinted polymer (NIP). This indicated that the suitable recognition sites were created in the IIP structure in the polymerization stage. Various factors, effective on the response behavior of the electrode, were investigated and optimized. The introduced sensor showed a linear range of 1.0 × 10(-9) to 8.1 × 10(-7)M and detection limit of 6.0 × 10(-10)M (S/N=3). The sensor was successfully applied for the trace lead determination in different samples.

Development of andrographolide molecularly imprinted polymer for solid-phase extraction

A method employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) to pretreat samples was developed. The polymers were prepared by precipitation polymerization with andrographolide as template molecule. The structure of MIP was characterized and its static adsorption capacity was measured by the Scatchard equation. In comparison with C(18)-SPE and non-imprinted polymer (NIP) SPE column, MIP-SPE column displays high selectivity and good affinity for andrographolide and dehydroandrographolide for extract of herb Andrographis paniculata (Burm.f.) Nees (APN). MIP-SPE column capacity was 11.9±0.6 μmol/g and 12.1±0.5 μmol/g for andrographolide and dehydroandrographolide, respectively and was 2-3 times higher than that of other two columns. The precision and accuracy of the method developed were satisfactory with recoveries between 96.4% and 103.8% (RSD 3.1-4.3%, n=5) and 96.0% and 104.2% (RSD 2.9-3.7%, n=5) for andrographolide and dehydroandrographolide, respectively. Various real samples were employed to confirm the feasibility of method. This developed method demonstrates the potential of molecularly imprinted solid phase extraction for rapid, selective, and effective sample pretreatment.

Preparation of cellulose magnetic microspheres with "the smallest critical size" and their application for microbial immunocapture

The goal of this paper is to introduce a universal method for quantitative control of the particle size of magnetic cellulose microspheres (MCMS) and to produce an optimal antibody absorption capability as an aid in the research of new applications of MCMS in immunomagnetic capture. In this study, "the smallest critical size theory" (TSCS) was proposed, tested, and confirmed by IgG-carrying capability measurements, magnetic response analysis, immunomagnetic capture, and PCR identification of bacteria. A Gaussian expression was proposed and used to guide the preparation of MCMS of the smallest critical size (SCS). The results showed that the diameter of the SCS of MCMS in this study was 5.82 mum, while the IgG absorption capability of the MCMS with SCS was 186.8 mg/mL. In addition, its high sensitivity and the efficiency of immunomagnetic capture of Salmonella bacteria exhibited another new application for MCMS.

Ion mobility spectrometry as a detector for molecular imprinted polymer separation and metronidazole determination in pharmaceutical and human serum samples

Application of ion mobility spectrometry (IMS) as the detection technique for a separation method based on molecular imprinted polymer (MIP) was investigated and evaluated for the first time. On the basis of the results obtained in this work, the MIP-IMS system can be used as a powerful technique for separation, preconcentration, and detection of the metronidazole drug in pharmaceutical and human serum samples. The method is exhaustively validated in terms of sensitivity, selectivity, recovery, reproducibility, and column capacity. The linear dynamic range of 0.05-70.00 microg/mL was obtained for the determination of metronidazole with IMS. The recovery of analyzed drug was calculated to be above 89%, and the relative standard deviation (RSD) was lower than 6% for all experiments. Various real samples were analyzed with the coupled techniques, and the results obtained revealed the efficient cleanup of the samples using MIP separation before the analysis by IMS as a detection technique.

Synthesis and evaluation of a molecularly imprinted polymer for 2,4-dinitrophenol

Molecular imprinted polymers (MIP) are considered one of the most promising selective and novel separation methods for removal phenolic compound in wastewater treatment. MIP are crosslinked polymeric materials that exhibit high binding capacity and selectivity towards a target molecule (template), purposely present during the synthesis process. In this work MIP were prepared in a bulk polymerization method in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide as template, functional monomer, cross-linker and initiator, respectively. An adsorption process for removal of nitrophenol using the fabricated MIP was evaluated under various pH and time conditions. The parameters studied for 2,4-dinitrophenol includes adsorption kinetics, adsorption isotherm, and selectivity. The maximum adsorption of nitrophenol by the fabricated MIP was 3.50 mg/g. The adsorption of 2,4-dinitrophenol by the fabricated MIP was found effective at pH 6.0. A kinetics study showed that nitrophenol adsorption follows a second order adsorption rate and the adsorption isotherm data is explained well by the Langmuir model.

A novel solid phase for selective separation of flavonoid compounds

A novel straightforward approach to selective separation for flavonoid compounds was reported. The solid phase material was prepared by copolymerization using allyl-bromide-modified chitosan as macromonomer, and ethylene glycol dimethacrylate as cross-linker. The material was evaluated by chromatographic analysis; it exhibited high selectivity separation for quercetin and its structural analogues using different mobile phases. The material could directly trap a specific class of compounds including quercetin and kaempferol from the hydrolyzate of Ginkgo biloba extract. These results demonstrated the possibility of direct extraction of certain constituents from herb using this material.

Uniformly-sized, molecularly imprinted polymers for (−)-epigallocatechin gallate, -epicatechin gallate and -gallocatechin gallate by multi-step swelling and polymerization method

Uniformly-sized, molecularly imprinted polymers (MIPs) for (-)-epigallocatechin gallate (EGCg), -epicatechin gallate (ECg) and -gallocatechin gallate (GCg) were prepared by a multi-step swelling and polymerization method using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and cyclohexanol as a porogen. Molecular recognition abilities of the obtained MIPs were evaluated in liquid chromatography using a mixture of ethanol and water, or ethanol as the eluent. Each MIP gave the highest molecular recognition ability for the respective template molecule. In addition, (-)-EGCg and -ECg had the same configuration (2R,3R) at positions 2 and 3, and therefore resulting in high cross reactivity each other. However, (-)-GCg, which has different configuration at position 2 with (-)-EGCg and -ECg, showed low cross reactivity with them. On the other hand, those MIPs showed no molecular recognition against (-)-epigallocatechin and -epicatechin, which have no gallate group at position 3. These results indicate that the MIPs prepared can recognize configuration at position 2 and a gallate group at position 3. Furthermore, the MIP for (-)-GCg could be successfully used for isolating (-)-EGCg and -ECg from green tea extract.

Recent advances on noncovalent molecular imprints for affinity separations

Molecularly imprinted polymers (MIPs) are tailor-made synthetic materials capable of selectively rebinding a target analyte, or a group of structurally related compounds based on a combination of recognition mechanisms including size, shape, and functionality. Among the advantageous properties of MIPs are the achievable specific affinity, the relative ease of preparation, and their mechanical and chemical robustness, which renders them ideal materials for applications as stationary phase (e. g., affinity chromatography or SPE), or as antibody mimics (e. g., biomimetic assays). Here, we review recent advancements on the application of MIPs in affinity separations and biomimetic assays, which have focused on the synthesis of size- and shape-uniform particles facilitating reproducibility, improved binding site accessibility, and enhanced affinity. While MIPs certainly offer promising potential as selective separation phase in a variety of applications, deeper understanding of the fundamental interactions governing imprinting, and rational understanding of the imprinting mechanism has yet to be achieved for providing rational guidelines in deliberately designing next-generation MIP materials.