Synthesis Of Molecularly Imprinted Polymers Research Articles

Surface molecularly imprinted polymer microspheres based on nano‐TiO2 for selective recognition of kaempferol

ABSTRACTThe molecular imprinting technique is a new method for preparing molecularly imprinted polymers (MIPs) with specific molecular recognition sites for certain target molecules. In this study, a novel, facile preparation method was presented, called “seed precipitation polymerization,” for the synthesis of MIPs via surface imprinting and a support matrix. In the polymerization process, kaempferol was used as the template molecule, methacrylic acid as the functional monomer, nano‐TiO2 as the support, azodiisobutyronitrile as the initiator, and ethylene glycol dimethacrylate as the crosslinker in acetonitrile solvent. The synthesized T‐MIP and MIP were analyzed by infrared spectroscopy and scanning electron microscopy. In addition, the obtained polymers were evaluated by adsorption isotherms and dynamic curves for their selective recognition properties for kaempferol. The results show that T‐MIP shows regular spherical particles; the adsorption dynamic curves of T‐MIP show that the adsorption capacity increases with time and reaches a maximum value and then finally reaches equilibrium, and the T‐MIP exhibits a higher affinity for kaempferol than does the MIP. The adsorption follows pseudo‐second‐order kinetics, the Freundlich adsorption equation fits the experimental data well, and there is strong evidence for multiple‐layer adsorption. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44888.

Preparation of well-defined erythromycin imprinted non-woven fabrics via radiation-induced RAFT-mediated grafting

Radiation-induced RAFT polymerization technique was applied to synthesize well-defined molecularly imprinted polymers (MIPs) of erythromycin (ERY). Methacrylic acid (MAA) was grafted onto porous polyethylene (PE)/polypropylene (PP) nonwoven fabrics, under γ-irradiation by employing 2-pheny-2-propyl benzodithioate as the RAFT agent and ethylene glycol dimethacrylate (EGDMA) as the crosslinker. MAA/erythromycin ratios of 2/1, 4/1, 6/1 were tested to optimize the synthesis of MIPs. The highest binding capacity was encountered at a MAA/ERY ratio of 4/1. Non-imprinted polymers (NIPs) were also synthesized in the absence of ERY. The MIPs synthesized by RAFT method presented a better binding capacity compared to those prepared by conventional method where no RAFT agent was employed.

Molecularly Imprinted Polymer (MIP): A Promising Recognition System for Development of Optical Sensor for Textile Dyes

An alternative for determination of dyes is the biomimetic sensors development with optical transduction, employing molecularly imprinted polymers (MIP) as recognition system. This work shows the MIP synthesis for the textile dye Acid Green 16 and the results of rebinding, selectivity and application of this MIP in textile effluent. The imprinted polymer presented rebinding of 83% and imprinted factor of 6.91, great selectivity and recovery next to 100%. Due to the excellent performance of this MIP, it can be a promisingsynthetic recognizer in the development of optical biomimetic sensors based on optical fibers.

Molecularly imprinted polymeric adsorbent for β-blockers removal synthesized using functionalized MSU-F silica as a sacrificial template

ABSTRACTThe growing demand for even more sensitive analytical techniques resulted in the development of molecularly imprinted polymers (MIPs) as adsorbents in solid-phase extraction. In this work, the preparation of polymer by combining synthesis of noncovalent MIPs and hard template technique is presented. Modified structured silica was used during polymerization of methacrylic acid and ethylene glycol dimethacrylate. After dissolution of silica, material was characterized and sorption studies were performed. Results confirmed that use of silica allows to design the polymer porous structure, obtained cavities are complementary to the template and approximately fourfold increase of sorption capacity comparing to non-imprinted polymer was achieved.

ChemInform Abstract: Precipitation Polymerization: A Versatile Tool for Preparing Molecularly Imprinted Polymer Beads for Chromatography Applications

AbstractReview: 116 refs.

Preparation and Characterization of a Molecularly Imprinted Polymer for Selective Recognition of Trichlorfon and Monocrotophos

ABSTRACTIn this study, a molecularly imprinted polymer (MIP) that can selectively recognize both the trichlorfon and the structurally related compound of monocrotophos pesticides was prepared using mixtures of trichlorfon and monocrotophos as template molecules, methacrylic acid (MAA) as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. The polymerization conditions had an important influence on the adsorption ability of imprinted polymer. When the ratio of trichlorfon and monocrotophos was 1.5:1 (mol/mol), the MIP had high adsorption capacity. The prepared polymers were characterized by Fourier transform infrared spectroscopy and static and kinetic adsorption experiments. The results indicated that the P = O groups of trichlorfon and monocrotophos reacted with the -OH groups of MAA during the synthesis of MIP. The imprinted polymer exhibited good recognition ability and higher selectivity toward trichlorfon and monocrotophos than the structurally related pesticide compounds of acephate and methamidophos, and offered fast kinetics for solid phase by the MIP adsorption of trichlorfon and monocrotophos from liquid phase.

Molecularly imprinted polymer particles: Formation, characterization and application

Molecularly imprinted polymer (MIP) particles offer many advantages as recognition objects. Therefore, we examined thoroughly the effect of various experimental parameters including cross-linker concentration, nature of solvent, type of template and its concentration, reaction volume and temperature on the formation of particulate MIPs using precipitation polymerization. The particles were characterized by various methods, such as XHR-SEM, HR-TEM and BET. Statistical calculations were carried out using ImageJ software over population of at least 200 particles in each experiment. The reproducibility of MIP synthesis was examined and the SD was better than 10%. MIP particles were imprinted with different Sudan dye derivatives (Sudan II, III, IV and Sudan orange G). Raman and FTIR spectroscopies were used to prove the successful imprinting. Reuptake measurements were carefully compared between non-imprinted molecularly polymer (NIP) and MIP particles employing the same quantity and similar diameter and polydispersity of NIP and MIP, as never reported before. The results showed that MIP particles imprinted by Sudan IV showed higher selectivity toward this specific dye as compared with MIPs imprinted by other Sudan dyes and NIPs.

Theoretical investigation on functional monomer and solvent selection for molecular imprinting of tramadol

The purpose of this Letter was to study for the first time the interaction process of tramadol (TRM) with distinct functional monomers (FM) in the formation of molecular imprinted polymer (MIP), using density functional theory (DFT) calculations at B3LYP/6-31G(d,p). As result we were able to establish that the best MIP synthesis conditions are obtained with acrylic acid as FM in 1:3 molar ratio and with chloroform as solvent. This condition presented the lowest stabilization energy for the pre-polymerization complexes. Besides, the intermolecular hydrogen bonds found between the template molecule and functional monomers play a primary role to the complex stability.

Efficient Molecular Imprinting Strategy for Quantitative Targeted Proteomics of Human Transferrin Receptor in Depleted Human Serum.

Soluble transferrin receptor (sTfR) in serum has been suggested as a marker for breast cancer diagnosis, monitoring and treatment. However, sTfR levels in some situations could be far below the limit of quantification (LOQ) of most assays. Thus, an efficient sample pretreatment strategy is required. In this study, molecularly imprinted polymers (MIPs) were developed and coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics for sTfR measurement. The key to this effort was that the same surrogate peptide of sTfR (VEYHFLSPYVSPK, VK13) was employed in both the enrichment by MIPs and the quantification by targeted proteomics. Specifically, three peptide templates with different lengths were evaluated for the synthesis of MIPs, and the imprinting conditions were optimized. The characteristics of MIPs, including the adsorption capacity, adsorption kinetics, and binding selectivity, were also investigated. As a result, a ∼12-fold enhancement of sensitivity was achieved using MIPs. An LOQ of 200 ng·mL(-1) was obtained. The intra- and interday precision were <10.7 and 7.8%, respectively. The accuracy was 7.5% at the lower limit of quantification (LLOQ) and <8.4% for the other QC levels. After validation, the assay was applied to determine the sTfR levels in breast cancer patients (n = 20) and healthy volunteers (n = 20) using the standard addition method. The corresponding levels of sTfR were 1.59 ± 0.36 μg·mL(-1) (range: 0.96-2.34 μg·mL(-1)) in the volunteers and 1.82 ± 0.42 μg·mL(-1) (range: 0.95-2.47 μg·mL(-1)) in the patients. This study is among the first to combine MIPs and LC-MS/MS targeted proteomics for protein quantification at the peptide level.

The different conformations and crystal structures of dihydroergocristine

The identification of different forms of dihydroergocristine (DHEC) was carried out by crystallization from different organic solvents. DHEC was identified as potential template for molecularly imprinted polymers (MIPs) for the epimeric specific analysis of ergot alkaloids (EAs) in food. DHEC was crystallized from different solvents in order to mimic the typical MIP synthesis conditions. Four new solvatomorphs of DHEC were obtained. All solvatomorphs contain a water molecule in the crystal structure, whereas three compounds contain an additional solvent molecule. Based on the conformation of DHEC a comparison with typical EA molecules was possible. The analysis showed that DHEC is a suitable template for MIPs for EAs.

Surface imprinted bacterial cellulose nanofibers for cytochrome c purification

Molecularly imprinted polymers possessing synthetic recognition sites present great potential for various application areas, which require specific recognition of molecules. However various molecularly imprinted polymers (MIPs) reported previously have low affinity capacity and low binding kinetics due to weak interactions between template molecule and functional monomer in aqueous media and also high mass transfer resistance. The synthesis of MIPs onto nanomaterial surface via metal ion coordination interactions serves as an effective solution. In this work, we prepared thin molecularly imprinted polymer layer on bacterial cellulose nanofiber surface using Cu2+ chelating monomer, N-Methacryloyl-(L)-histidinemethylester (MAH) as a functional monomer orienting cytochrome c molecules. The conditions of polymerization and adsorption were optimized to obtain best affinity performance. Due to unique properties of bacterial cellulose nanofibers such as high surface-to-volume ratio and macro-porosity, the resultant cytochrome c imprinted nanofibers (Cyt c-MIP NFs) reducing diffusional resistances could achieve high recognition capacity and excellent binding kinetics. Cyt c-MIP NFs were also successfully applied to capture template proteins from real sample. This novel procedure presents simple, cheap and stable fabrication strategy for efficient separation of proteins.

Molecularly imprinted polymers by reversible chain transfer catalysed polymerization

Molecularly imprinted polymers (MIPs) are tailor-made biomimetic receptors obtained by polymerization in the presence of molecular templates. They contain binding sites for target molecules with affinities and specificities on a par with those of antibodies, hormone receptors or enzymes. Mainly synthesized via radical polymerization of vinyl monomers, MIPs have also recently taken advantage of the introduction of modern methods of controlled/living radical polymerization (CRPs). In this paper, we report for the first time the use for MIP synthesis of a recently developed CRP method based on an iodide-transfer polymerization with a reversible activation mechanism, referred to as Reversible chain-Transfer Catalysed Polymerization (RTCP). Using S-propranolol as model template, we show that this technique is a convenient method for the synthesis of MIPs, both in the format of bulk polymers and nanoparticles, yielding polymers with reactive chain ends for an easy surface functionalization.

Rational design of molecularly imprinted polymers for recognition of cannabinoids: A structure–property relationship study

Molecular modeling studies were performed to investigate the molecular interactions between the molecules of template (Δ9-tetrahydrocannabinol – Δ9-THC – and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol – THC-COOH) and the reagents of synthesis commonly employed in the preparation of molecularly imprinted polymers (MIP), as functional monomer, porogenic solvent and the cross linker. The electronic interaction energy (ΔE) between the templates and the possible reagents of synthesis was evaluated using the DFT method with B3LYP functional and the basis set 6-311G(d,p), considering that for a given template, a monomer that results in the largest value of ΔE is the most suitable for the synthesis. The solvent effect was also included using the Polarizable Continuum Model and the choice of the most suitable solvent was based on the smallest value of ΔEsolv. It was shown that for both templates, the functional monomer acrylic acid (AA) provided the largest ΔE, while the functional monomer 4-vinylpyridine (4-VPy) provided the smallest one. For choosing the porogenic solvent, chloroform showed the smallest ΔEsolv. Thus, the use of AA as monomer and chloroform as porogenic solvent is expected to result in a better MIP rebinding properties and selectivity rather than MIP synthesized with the other monomers and solvents. The main interactions between the molecules of template and monomers in each interaction site and the correlation between ΔE values and the charge variation in these sites were also analyzed. The results in this study provided a better understanding on the events that may occur during the imprinting process and may be useful in the rational choice of the best conditions for the synthesis of MIPs, which could be applied in the selective detection of Δ9-THC and THC-COOH.

Ion-exchange molecularly imprinted polymer for the extraction of negatively charged acesulfame from wastewater samples

Acesulfame is a known indicator that is used to identify the introduction of domestic wastewater into water systems. It is negatively charged and highly water-soluble at environmental pH values. In this study, a molecularly imprinted polymer (MIP) was synthesized for negatively charged acesulfame and successfully applied for the selective solid phase extraction (SPE) of acesulfame from influent and effluent wastewater samples. (Vinylbenzyl)trimethylammonium chloride (VBTA) was used as a novel phase transfer reagent, which enhanced the solubility of negatively charged acesulfame in the organic solvent (porogen) and served as a functional monomer in MIP synthesis. Different molecularly imprinted polymers were synthesized to optimize the extraction capability of acesulfame. The different materials were evaluated using equilibrium rebinding experiments, selectivity experiments and scanning electron microscopy (SEM). The most efficient MIP was used in a molecularly imprinted-solid phase extraction (MISPE) protocol to extract acesulfame from wastewater samples. Using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) analysis, detection and quantification limits were achieved at 0.12μgL−1 and 0.35μgL−1, respectively. Certain cross selectivity for the chemical compounds containing negatively charged sulfonamide functional group was observed during selectivity experiments.

Molecularly imprinted polymers for cleanup and selective extraction of curcuminoids in medicinal herbal extracts.

This paper describes the synthesis of novel molecularly imprinted polymers (MIPs), prepared by a noncovalent imprinting approach, for cleanup and preconcentration of curcumin (CUR) and bisdemethoxycurcumin (BDMC) from medicinal herbal extracts and further analysis by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Two molecular mimics, a mixture of reduced BDMCs and 4-(4-hydroxyphenyl)-2-butanone (HPB), have been synthesized and applied as templates for MIP synthesis. The polymers were prepared using N-(2-aminoethyl) methacrylamide (EAMA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker (in a 1:5 molar ratio), and a mixture of acetonitrile/dimethylsulfoxide (90%, v/v) as porogen. MIPs prepared using a mixture of reduced BDMCs as template showed higher selectivity for CUR and BDMC than those obtained with HPB, with imprinting factors of 3.5 and 2.7 for CUR and BDMC, respectively, using H2O/acetonitrile (65:35, v/v) as mobile phase. The adsorption isotherms for CUR in the MIP and the nonimprinted polymer (NIP) were fitted to the Freundlich isotherm model, and the calculated average binding affinities for CUR were (17 ± 2) and (8 ± 1) mM(-1) for the MIP and the NIP, respectively. The polymers were packed into solid-phase extraction (SPE) cartridges, and the optimized molecularly imprinted solid-phase extraction (MISPE-HPLC) with fluorescence detection (FLD) method allowed the extraction of both curcuminoids from aqueous samples (50 mM NH4Ac, pH 8.8) followed by a selective washing with acetonitrile/NH4Ac, 50 mM at pH 8.8 (30:70%, v/v), and elution with 3 × 1 mL of MeOH. Good recoveries and precision ranging between 87 and 92%, with relative standard deviation (RSD) of <5.3% (n = 3), were obtained after the preconcentration of 10-mL solutions containing both CUR and BDMC at concentrations in the range of 0-500 μg L(-1). The optimized method has been applied to the analysis of both curcuminoids in medicinal herbal extracts.

Correlation study between molecular structure of sesquiterpene lactones and the selective adsorption performance of molecularly imprinted polymers

We preliminarily report that the structure of template molecules and target components correlates with the selective adsorption performance of molecularly imprinted polymer (MIPs) in sesquiterpene lactones. Template molecules involved three categories of sesquiterpene lactones with distinct ring systems: 5-mem lactone ring atractylenolide III, 7-mem lactone ring dehydrocostus lactone, and 10-mem lactone ring costunolide lactone, of which the conformations were verified by variable-temperature 1H NMR spectroscopy. Reciprocal MIPs were prepared by precipitation polymerization and employed as selective sorbents in the columns of solid phase extraction (SPE). These columns were further used for enriching the mixed adsorption solution of sesquiterpene lactone ingredients and reference components. Finally, the extract of Radix Aucklandiae, a Chinese medicine herb, was used to verify the efficiency of this method. Our results demonstrate that the steric conformational stability of molecules is associated with the selective adsorption of their corresponding MIPs. We have further observed that the maximum adsorption capacity occurs when the target molecule conformation is consistent with that of the template molecule. The addition of more hydrophilic groups correlates with weaker adsorption of MIPs. Our findings provide important information to help guide the selection of appropriate template molecules for synthesis of MIPs with specific adsorption.

Synthesis and characterization of molecularly imprinted polymers for the remediation of PCBs and dioxins in aqueous environments.

This paper, reports on the approach devised to remediate water sources contaminated with PCBs and dioxins. The approach reported is based on the synthesis of highly selective molecularly imprinted polymers (MIPs). The paper elaborates the materials, procedures and protocols devised and followed for the synthesis of MIPs. The characterization of the synthesized MIPs and NIPs were performed using a number of techniques, such as FTIR, SEM, etc. The FTIR results show a broad OH stretching vibration peaks associated with methacrylic acid carboxylic group (COOH). at 3710 cm-1 for NIP and 3588 cm-1 for MIP, -CH2 stretching peak at 2953 cm-1for NIP, peaks due to the presence of methylene group in both MAA and EDMA appearing at 2951 cm-1 for MIP. The carbonyl group C = O stretching peak was observed in both MIP and NIP at 1721 cm-1 and this might have originated from MAA and EDMA respectively in both MIP and NIP. Weak combination bands from 1637 cm-1 to 1249 cm-1 and sharp bands at 1143 cm-1 specifically on MIPs spectra indicated the presence of aromatic ring of the template. The surface area of MIP was found to be 74.0010 m2/g, thus larger than that for NIP which was 58.6519 m2/g due to the presence of cavities on MIPs. The fit of the Langmuir model was found to be r 2 = 0.5842 while Freundlich model were found to be r2 = 0.3241, signifying that better correlation was with Langmuir than Freundlich.

Molecularly imprinted polymers with novel functional monomer for selective solid-phase extraction of gastrodin from the aqueous extract of Gastrodia elata

Molecular imprinted polymers (MIPs) with high selectivity and affinity to gastrodin in water were designed using allyl 2,3,4,6-tetra-O-acetyl-glucopyranoside (TAGL) and 1,2,3,4,5-pentafluoro-6-vinylbenzene (PFVB) as novel functional monomers. Binding characterization of pre-polymerization complexes was researched by nuclear magnetic resonance (NMR) and the MIPs were characterized by scanning electron microscopy (SEM). The properties involving adsorption isotherm, adsorption kinetics and selective recognition capacity were evaluated. The MIPs/TAGL exhibited good site accessibility in which it only took 30min to achieve adsorption equilibrium and highly selective recognition for the template. Furthermore, the performance of the MIPs/TAGL as solid phase extraction material was investigated in detail and hot water at 50°C served as the eluting solvent. Pure gastrodin with the recovery of 76.6% was obtained from the aqueous extract of Gastrodia elata roots.

Tailor-made molecularly imprinted polymers for dimethoate and deltamethrin recognition: synthesis, characterization and chromatographic evaluation

This work concerns the development of molecularly imprinted polymers (MIPs) for the selective extraction of dimethoate (dmt) and deltamethrin (dm) from food matrices. To achieve this goal, the non-covalent methodology has been applied for the preparation of MIPs using metacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) and triethylene glycol dimethacrylate (TEGDMA) as cross-linkers in order to evaluate the influence of the nature of the cross-linker on the efficiency and selectivity of those MIPs for the target pesticides. Non-imprinted polymers (NIPs), which do not contain template, have been also prepared in parallel with the MIP synthesis using the same synthetic protocol to assess the specificity of the interactions. Chemical and physical characterization was carried out using conventional techniques, such as Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). Morphological characterization of MIPs and NIPs has been also performed using scanning electron microscopy (SEM) in order to assess the polymer’s surface topography. The performance of each polymer was evaluated by conducting binding property measurements, namely imprinting factor determinations and adsorption studies using high performance liquid chromatography (HPLC). The results obtained in this study seem to show that there is a correlation between the polymer structure (including its physical characteristics) and their binding properties.

Quantum chemical density functional theory studies on the molecular structure and vibrational spectra of Gallic acid imprinted polymers

Gallic acid (GA) is known by its antioxidant, anticarcinogenic properties and scavenger activity against several types of harmful free radicals. Molecularly imprinted polymers (MIPs) are used in separation of a pure compound from complex matrices. A stable template–monomer complex generates the MIPs with the highest affinity and selectivity for the template. The quantum chemical computations based on density functional theory (DFT) was used on the template Gallic acid (GA), monomer acrylic acid (AA) and GA–AA complex to study the nature of interactions involved in the GA–AA complex. B3LYP/6-31+G(2d,2p) model chemistry was used to optimize their structures and frequency calculations. The effect of porogen acetonitrile (ACN) on complex formation was included by using polarizable continuum model (PCM). The results demonstrated the formation of a stable GA–AA complex through the intermolecular hydrogen bonding between carboxylic acid groups of GA and AA. The Mulliken atomic charge analysis and simulated vibrational spectra also supported the stable hydrogen bonding interaction between the carboxylic acid groups of GA and AA with minimal interference of porogen ACN. Further, simulations on GA–AA mole ratio revealed that 1:4 GA–AA was optimum for synthesis of MIP for GA.