Molecular imprinting polymerization by Fenton reaction

The aim of this study is the preparation of molecularly imprinted polymers by employing a redox pair as initiator system. Bulk molecularly imprinted polymers were synthesized by using Fenton reagents as initiator system. Theophylline, methacrylic acid, and ethylene glycol dimethacrylate were employed as model template, functional monomer, and crosslinking agent, respectively. Conventional imprinted polymers were also prepared by using 2,2′-azoisobutyronitrile in order to evaluate the efficiency of the proposed initiator system. Redox molecularly imprinted polymers and conventional molecularly imprinted polymers were characterized by water uptake measurement, while the imprinting effect of synthesized polymers were evaluated by performing binding experiments in organic (acetonitrile) and in water (buffered water solution at pH = 7.4) media.     

Selective enrichment and separation of phosphotyrosine peptides by thermosensitive molecularly imprinted polymers

Novel thermosensitive molecularly imprinted polymers were successfully prepared using the epitope imprinting approach in the presence of the mimic template phenylphosphonic acid, the functional monomer vinylphosphonic acid‐Ti⁴⁺, the temperature‐sensitive monomer N‐isopropylacrylamide and the crosslinker N,N′‐methylenebisacrylamide. The ratio of the template/thermosensitive monomers/crosslinker was optimized, and when the ratio was 2:2:1, the prepared thermosensitive molecularly imprinted polymers had the highest imprinting factor. The synthetic thermosensitive molecularly imprinted polymers were characterized by Fourier transform infrared spectroscopy to reveal the combination and elution processes of the template. Then, the adsorption capacity and thermosensitivity was measured. When the temperature was 28°C, the imprinting factor was the highest. The selectivity and adsorption capacity of the thermosensitive molecularly imprinted polymers for phosphotyrosine peptides from a mixture of three tailor‐made peptides were measured by high‐performance liquid chromatography. The results showed that the thermosensitive molecularly imprinted polymers have good selectivity for phosphotyrosine peptides. Finally, the imprinted hydrogels were applied to specifically adsorb phosphotyrosine peptides from a sample mixture containing phosphotyrosine and a tryptic digest of β‐casein, which demonstrated high selectivity. After four rebinding cycles, 78.9% adsorption efficiency was still retained.     

Preparation of bovine hemoglobin-imprinted polymer beads via the photografting surface-modified method

Molecularly imprinted polymers (MIPs), based on photografting surface-modified polystyrene beads as matrices, were prepared with acrylamide as the functional monomer, bovine hemoglobin as the template molecule and N, N′-methylene bisacrylamide as the crosslinker in a phosphate buffer. The results of IR, scanning electron microscope (SEM) and elemental analyses demonstrated the formation of a grafting polymer layer on the polystyrene-bead surface. Subsequent removal of the template left behind cavities on the surface of the polymer matrix with a shape and an arrangement of functional groups having complementary binding sites with the original template molecule. The adsorption studies showed that the imprinted polymers have a good adsorption capacity and specific recognition for bovine hemoglobin as the template molecule. Our results demonstrated that the polymer prepared via the photografting surface-modified method exhibited better selectivity for the template. Attempts to employ the new method in molecular imprinting techniques may introduce new applications for MIPs and facilitate probable protein separation and purification. __________ Translated from Chemical Journal of Chinese Universities, 2008, 29(1): 64–70     

Preconcentration of indapamide from human urine using molecularly imprinted solid‐phase extraction

A simple, sensitive, and selective molecularly imprinted solid‐phase extraction and spectrophotometric method has been developed for the clean‐up and preconcentration of indapamide from human urine. Molecularly imprinted polymers were prepared by a non‐covalent imprinting approach using indapamide as a template molecule, 2‐(trifluoromethyl) acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, N,N‐azobisisobutyronitrile as a thermal initiator and acetonitrile as a porogenic solvent. A non‐imprinted polymer was also prepared in the same way, but in the absence of template. Molecularly imprinted polymer and non‐imprinted polymer sorbents were dry‐packed into solid‐phase extraction cartridges. Eluates from cartridges were analyzed using a spectrophotometer for the determination of indapamide by referring to the calibration curve in the range 0.14–1.50 μg/mL. Preconcentration factor, limit of detection, and limit of quantification were 16.30, 0.025 μg/mL, and 0.075 μg/mL, respectively. A relatively high imprinting factor (9.3) was also achieved and recovery values for the indapamide spiked into human urine were in the range of 80.1–81.2%. In addition, relatively low within‐day (0.17–0.42%) and between‐day (1.1–1.4%) precision values were obtained as well. The proposed molecularly imprinted solid‐phase extraction and spectrophotometric method was successfully applied to selective extraction, preconcentration, and determination of indapamide from human urine samples.     

Inhibitory Effects of 2,6-Di-O-methyl-3-O-acetyl-β-cyclodextrins with Various Degrees of Substitution of Acetyl Group on Macrophage Activation and Endotoxin Shock Induced by Lipopolysaccharide

The effects of 2,6-di-O-methyl-3-O-acetyl-β-cyclodextrins (DMA-β-CyD) with various degrees of substitution (DS) of an acetyl group of 1.5, 3.8, 6.3 and 7, which are abbreviated to DMA2-β-CyD, DMA4-β-CyD, DMA6-β-CyD and DMA7-β-CyD, respectively, on murine macrophage activation and endotoxin shock induced by lipopolysaccharide (LPS) were examined. Of four DMA-β-CyDs used in the present study, cytotoxicity of DMA-β-CyDs in RAW264.7 cells, a murine macrophage-like cell line, decreased with an increase in the DS values of DMA-β-CyD, and DMA7-β-CyD had no cytotoxicity on RAW264.7 cells up to 100 mM. DMA2-β-CyD and DMA7-β-CyD at the concentration of 5 mM had greater inhibitory effects on nitric oxide (NO) production in RAW264.7 cells stimulated with LPS than DMA4-β-CyD and DMA6-β-CyD. In addition, these inhibitory effects of DMA2-β-CyD and DMA7-β-CyD were concentration-dependent. In the in vivo study, all of the mice died within 12 h after intraperitoneal administration of the solution containing LPS and d-galactosamine. When 100 mM DMA7-β-CyD was concomitantly administered with both LPS and d-galactosamine intraperitoneally in mice, the survival rate significantly increased, but DMA4-β-CyD and DMA6-β-CyD did not. In conclusion, we revealed that DS values of DMA-β-CyDs strikingly affect not only the cytotoxic activity but also the inhibitory effects of LPS-induced NO production in RAW264.7 cells and fatality of endotoxin shock mice induced by LPS and d-galactosamine. These results suggest the potential use of DMA7-β-CyD as an antagonist of LPS-induced endotoxin shock.     

Thermosensitive molecularly imprinted poly(1‐vinyl‐2‐pyrrolidone/methyl methacrylate/N‐vinylcaprolactam) for selective extraction of imatinib mesylate in human biological fluid

The efficiency of a molecularly imprinted polymer as a selective packing material for the solid‐phase extraction of imatinib mesylate sorption was investigated. The molecularly imprinted polymer was prepared using N,N′‐methylenebisacrylamide as a cross‐linker agent, N‐vinylcaprolactam as a thermo‐sensitive monomer, 1‐vinyl‐2‐pyrrolidone and methyl methacrylate as functional monomers, azobisisobutyronitrile as an initiator and imatinib mesylate as a template. The drug‐imprinted polymer was identified by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and scanning electron microscopy. It was found that this polymer can be used for determination of trace levels of imatinib mesylate with a recovery percentage that could reach over 90%. Furthermore, the synthesized molecularly imprinted polymer indicated higher selectivity towards imatinib mesylate than other compounds. From isotherm study, the equilibrium adsorption data of imatinib mesylate by imprinted polymer were analyzed by Langmuir, Freundlich, and Temkin isotherm models. The developed method was used for determination of imatinib mesylate in human fluid samples by high performance liquid chromatography with excellent results.     

Molecular Imprinting of Cyclodextrin on Silica-Gel Support for the Stationary Phase of High-Performance-Liquid-Chromatography

By copolymerizing acryloyl cyclodextrin (CD) andN,N'-methylenebisacrylamide with vinylated silica-gel in the presence of a template in water,a thin layer of molecularly imprinted CD polymer was immobilized on a porous silica-gel support. This mechanically weak polymer was reinforced by the silica-gel andsuccessfully used as a stationary phase in high-performance-liquid-chromatography (HPLC). When L-Phe-L-Phe was the template, the polymer/silica-gel conjugate retainedL-Phe-L-Phe in the aqueous eluent more strongly than D-Phe-D-Phe. As expected, the D-Phe-D-Phe-imprinted polymer retained D-Phe-D-Phe more strongly than L-Phe-L-Phe. Selective separation of antibiotics was also achieved by thepolymer/silica-gel conjugate. Molecularly imprinted CD polymer, immobilizedon silica-gel, is an eminent stationary phase for HPLC in water.     

Supramolecular recognition of estrogens via molecularly imprinted polymers

The isolation and preconcentration of estrogens from new types of biological samples (acellular and protein-free simulated body fluid) by molecularly imprinted solid-phase extraction has been described. In this technique, supramolecular receptors, namely molecularly imprinted polymers (MIPs) are used as a sorbent material. The recognition sites of MIPs were prepared by non-covalent multiple interactions and formed with the target 17β-estradiol as a template molecule. High-performance liquid chromatography with spectroscopic UV, selective, and a sensitive electrochemical CoulArray detector was used for the determination of 17β-estradiol, estrone, and estriol in simulated body fluid which mimicked human plasma.     

Molecularly imprinted polymers with synthetic dummy templates for the preparation of capsaicin and dihydrocapsaicin from chili peppers

In this work, dummy molecularly imprinted polymers with high selectivity and affinity to capsaicin and dihydrocapsaicin are designed using N‐vanillylnonanamide as a dummy template. The performance of dummy molecularly imprinted polymers and nonimprinted polymers was evaluated using adsorption isotherms, adsorption kinetics, and selective recognition capacity. Dummy molecularly imprinted polymers were found to exhibit good site accessibility, taking just 20 min to achieve adsorption equilibrium; they were also highly selective toward capsaicin and dihydrocapsaicin. We successfully used dummy molecularly imprinted polymers as a specific sorbent for selectively enriching capsaicin and dihydrocapsaicin from chili pepper samples. In a scaled‐up experiment, the selective recovery of capsaicinoids was calculated to be 77.8% using solid‐phase extraction. To the best of our knowledge, this is the first example of the use of N‐vanillylnonanamide as a dummy template in molecularly imprinted polymers to simultaneously enrich capsaicin and dihydrocapsaicin.     

修饰硅胶表面印迹牛血红蛋白及其识别性能的研究

本文选用马来酸酐修饰后的硅胶作为载体,丙烯酰胺为功能单体,N,N’-亚甲基双丙烯酰胺为交联剂,牛血红蛋白为模板分子,采用氧化还原悬浮聚合法,合成了具有选择性识别的牛血红蛋白分子印迹聚合物。并用红外光谱(IR)、扫描电子显微镜(SEM)对聚合物进行了表征,结果表明载体表面成功接枝了分子印迹聚合物薄层。同时,选择性吸附实验表明分子印迹聚合物的具有良好的识别性能,能成功的实现水溶液中牛血红蛋白的富集。     

Prominent Solubilizing Effect of 2-Hydroxypropyl-β-cyclodextrin on a New Thiazolidine Derivative (FPFS-410) with Antidiabetic and Lipid-lowering Activities through Inclusion Complex Formation

2-(N-Cyanoimino)-5-{(E)-4-styrylbenzylidene}-4-oxothiazolidine (FPFS-410) is a newly synthesized thiazolidine derivative having not only antidiabetic but also lipid-lowering activities. However, this compound has an extremely low aqueous solubility (2.8×10⁻⁸ M in phosphate buffer at 25 °C). In this study, we attempted to improve the solubility of FPFS-410 in water, by means of the complexation with 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD). Further, the interaction of FPFS-410 with HP-β-CyD in 50% v/v methanol/water mixed solution was investigated by ultraviolet and ¹H-nuclear magnetic resonance (NMR) spectroscopic methods, because the solubility of FPFS-410 in water was too low to study quantitatively the interaction. The results of the solubility method indicated that HP-β-CyD had a markedly high solubilizing ability to FPFS-410, e.g., the solubility of the compound was increased 200,000-fold by the addition of 40 mM HP-β-CyD. The continuous variation plot of the FPFS-410/HP-β-CyD system in 50% v/v methanol/water solution gave a maximum at a host/guest molar ratio of 1:1. ¹H-NMR spectroscopic studies suggested that the stilbene moiety of FPFS-410 is preferably included in the HP-β-CyD cavity to form the 1:1 complex in 50% v/v methanol/water solution. The present results suggest that HP-β-CyD is useful for improvement of the oral bioavailability of FPFS-410.     

Preparation and characterization of molecularly‐imprinted polymers for extraction of sanshool acid amide compounds followed by their separation from pepper oil resin derived from Chinese prickly ash (Zanthoxylum bungeanum)

Molecularly imprinted polymers were prepared using the molecular structure analogs of sanshool as template molecule, 2‐vinylpyridine and β‐cyclodextrin as double functional monomers, ethylene dimethacrylate as cross linker, and azobisisobutyronitrile as initiator. The structural characteristics of the polymers were determined by Fourier‐transform infrared spectroscopy and scanning electron microscopy. Dynamic adsorption and isothermal adsorption were also investigated. The molecularly imprinted polymers were used to prepare a molecularly imprinted solid‐phase extraction column in order to separate acid amide components from pepper oil resin derived from Chinese prickly ash (Zanthoxylum bungeanum). After eluting, the percentage of acid amide components was enhanced to 92.40 ± 1.41% compared with 23.34 ± 1.21% in the initial pepper oil resin, indicating good properties of purification of molecularly imprinted polymers and potential industrial application.     

Studies on the synthesis and properties of malachite green imprinted polymer

A new molecularly imprinted polymer was synthesized with malachite green (MG) as molecular template, methacrylic acid (MAA) as functional monomer, ethylene dimethacrylate (EDMA) as crosslinker, and azobisisobutyronitrile (AIBN) as initiator. Recognition properties of the MG imprinted polymer were studied by equilibrium adsorption and HPLC. The results showed that the imprinted polymer had good affinity and marked selectivity for MG, and can separate MG with its analogue commendably. The new polymer can be used for the enrichment of MG in complex sample, and can work as separation media to separate and detect MG by HPLC.     

Selective extraction of clonazepam from human plasma and urine samples by molecularly imprinted polymeric beads

A molecularly imprinted polymer (MIP) based on free‐radical polymerization was prepared with 1‐(N,N‐biscarboxymethyl)amino‐3‐allylglycerol and N,N‐dimethylacrylamide as functional monomers, N,N‐methylene diacrylamide as the cross‐linker, copper ion‐clonazepam as the template and 2,2‐azobis(2‐methylbutyronitrile) as the initiator. The imprinted polymer was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, and SEM. The MIP of agglomerated microparticles with multipores was used for SPE. The imprinted polymer sorbent was selective for clonazepam. The optimum pH and sorption capacity were 5 and 0.18 mg/g at 20°C, respectively. The profile of the drug uptake by the sorbent reflects good accessibility of the active sites in the imprinted polymer sorbent. The MIP‐SPE was the most feasible technique for the extraction of clonazepam with a high recovery from human plasma and urine samples.     

Surface-initiated molecularly imprinted polymeric column: In situ synthesis and application for semi-preparative separation by high performance liquid chromatography

In this work, we prepared a monolithic and surface initiated molecularly imprinted polymeric (MIP) column for HPLC and explored its application for template separation from plant extract. The silica beads (40-60 μm) were coupled with initiator on the surface and then packed in to a stainless steel HPLC column. The pre-polymerization mixture (the template, functional monomer and crosslinker were emodin, acrylamide and divinylbenzene, respectively) was injected into the column and polymerized by thermal initiation. The prepared MIP column exhibited excellent retention capability and large imprinted factor for template (the retention time and imprinted factor for emodin on MIP column were 16.26 min and 7.21, respectively). Moreover, the emodin-molecularly imprinted polymeric column could be applied to separate emodin from alcohol extract of Rheum palmatum L. at semi-preparative scale and 1.2 mg of emodin was obtained in 4 h.     

Preparation of highly selective solid-phase extractants for Cibacron reactive dyes using molecularly imprinted polymers

Selective polymeric extractants were prepared for preconcentration of Cibacron reactive red dye, a dye that is often applied with Cibacron reactive blue and Cibacron reactive yellow for dyeing of fabrics. The best extractant was fabricated (in chloroform) using methacrylic acid (as monomer), ethylene glycol dimethacrylate (as crosslinker), AIBN (as initiator for polymerization), and red dye as template molecule, with a molar stoichiometric ratio of 8.0:40.0:2.5:0.63, respectively. The structure of the molecularly imprinted polymer (MIP) was robust, and resisted dissolution up to 260 °C. Compared with the un-imprinted polymer, the imprinted product has a large specific surface area which improved its adsorption capacity. The effect of imprinting was obvious from the adsorption capacity measured at pH 4 for red dye (the imprinted molecule), which was increased from 24.0 to 79.3 mg g⁻¹ after imprinting. Equilibrium adsorption studies revealed that the dye-imprinted-polymer enables efficient extraction of red dye even in the presence of blue and yellow dyes which have similar chemical natures to the red dye. The selectivity coefficients S _{red dye/dye}, were 13.9 and 17.1 relative to the yellow and blue dyes, respectively. The MIP was found to be effective for red dye preconcentration, with a preconcentration factor of 100, from tap water and treated textile wastewater. The factors affecting extraction of red dye by the MIP were studied and optimized. Under the optimized extraction conditions, red dye was selectively quantified in the presence of other competing dyes at a concentration of 20 μg L⁻¹ from different water systems with satisfactory recoveries (91–95%) and RSD values (∼5.0%).     

Molecularly imprinted polymers for selective extraction of synephrine from Aurantii Fructus Immaturus

In this work, molecularly imprinted solid-phase extraction (MISPE) has been used to selectively enrich, purify, or remove synephrine from Aurantii Fructus Immaturus. To this end, a molecularly imprinted polymer (MIP) was prepared by self-assembly from the template synephrine, the functional monomer methacrylic acid, and the crosslinker ethylene glycol dimethacrylate in 1:4:20 molar ratio. Subsequent molecular interrogation of the MIP binding sites revealed preferential structural selectivity for synephrine relative to other structurally related naturally occurring compounds (i.e. octopamine and tyramine ). This selectivity was subsequently exploited to achieve substantial sample clean-up of extracts of crude Aurantii Fructus Immaturus and Aurantii Fructus Immaturus stir-baked with bran. The purity of synephrine in the extracts after MISPE represented approximately 24.21-fold enrichment of the synephrine in the untreated extracts of Aurantii Fructus Immaturus stir-baked with bran. High recoveries (85–90%) from the samples proved that the method was valid for selective enrichment, purification, or removal of synephrine from Aurantii Fructus Immaturus.     

Isolation of sinapic acid from broccoli using molecularly imprinted polymers

A molecularly imprinted polymer was synthesized for the purpose of sinapic acid isolation from Egyptian nutraceutical Botrytis italica, L. (broccoli) due to its prominent medicinal and wide pharmacological activities. A computational study was first developed to determine the optimal template to functional monomer molar ratio. Based on the computational results, five polymers were synthesized using a bulk polymerization method with sinapic acid as the template molecule. Evaluation of the synthesized polymers binding performance was carried out using batch rebinding assay, which revealed that the molecularly imprinted polymer of molar ratio (1:4:20), template to functional monomer (4‐vinyl pyridine) to crosslinker (ethylene glycol dimethacrylate) was of optimum performance, thus, this polymer was applied for sinapic acid isolation from closely related analogues. This represents a more practical approach to isolate sinapic acid from different natural extracts selectively.     

Ability of a salivary intrinsically unstructured protein to bind different tannin targets revealed by mass spectrometry

Superporous monolithic hydrogels (cryogel monoliths) are elastic, sponge-like materials that can be prepared in an aqueous medium through a cryotropic gelation technique. These monoliths show interesting properties for the development of high-throughput solid-phase extraction supports to treat large volumes of aqueous samples. In this work, a cryogel-supported molecularly imprinted solid-phase extraction approach for the endocrine disruptor bisphenol A (BPA) from river water and wine samples is presented. An imprinted polymer with molecular recognition properties for BPA was prepared in acetonitrile by thermal polymerization of a mixture of 4,4′-dihydroxy-2,2-diphenyl-1,1,1,3,3,3-trifluoropropane as a mimic template of BPA, 4-vinylpyridine and trimethylolpropane trimethacrylate in a molar ratio of 1 + 6 + 6. Fine imprinted particles (<10 μm) were embedded in a poly-acrylamide-co-N,N′-methylenbisacrylamide cryogel obtained by ammonium persulfate-induced cryopolymerization at −18 °C. The resulting monolithic gel was evaluated for its use as a sorbent support in an off-line solid-phase extraction approach to recover BPA from dilute aqueous samples with minimum pre-loading work-up. The optimized extraction protocol resulted in a reliable MISPE method suitable to selectively extract and preconcentrate BPA from river water and red wine samples, demonstrating the practical feasibility of cryogel-trapped imprinted polymers as solid-phase extraction materials     

Development of a molecularly imprinted solid‐phase extraction sorbent for the selective extraction of telmisartan from human urine

A novel molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed for the selective extraction of telmisartan from human urine. Molecularly imprinted polymers were prepared by a noncovalent imprinting approach through UV‐radical polymerization using telmisartan as a template molecule, 2‐dimethylamino ethyl methacrylate as a functional monomer, ethylene glycol dimethacrylate as a cross‐linker, N,N‐azobisisobutyronitrile as an initiator, chloroform as a porogen. Molecularly imprinted polymers and nonimprinted control polymer sorbents were dry‐packed into solid‐phase extraction cartridges, and eluates from cartridges were analyzed using a spectrofluorimeter. Limit of detection and limit of quantitation values were 11.0 and 36.0 ng/mL, respectively. A very high imprinting factor (16.1) was achieved and recovery values for the telmisartan spiked in human urine were in the range of 76.1–79.1%. In addition, relatively low within‐day (0.14–1.6%) and between‐day (0.11–1.31%) precision values were obtained. Valsartan was used to evaluate the selectivity of sorbent as well. As a result, a sensitive, selective, and simple molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed and successfully applied to the direct determination telmisartan in human urine.