Synthesis and characterization of a novel quercetin magnetic molecularly imprinted polymer via reversible addition fragmentation chain transfer strategy

Molecularly imprinted polymer (MIP) will be modified on the surface of the core-shell structure silica magnetic nanoparticles, during which quercetin is used as a template molecule, acrylamide as a functional monomer, azo-bisisobutyronitrile as an initiator and ethylene glycol dimethacrylate as a cross-linker, to synthesize highly efficient and selective quercetin magnetic molecularly imprinted nanoparticles via Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. FT-IR and X-ray diffraction (XRD) patterns are used to monitor the reaction and show the characteristic groups of each reaction step. Compared with the conventional bulk polymerization (2.7029 mg/g), the adsorption test showed that the MMIP by RAFT activity controlled polymerization had better absorption capacity for quercetin which the saturated adsorption amount was 4.8471 mg/g. Kinetic studies indicate that pseudo first order model is suitable to describe the adsorption mechanism. Thermodynamics experiment revealed that Langmuir model was more applied for explains the adsorption of quercetin onto magnetic molecularly imprinted polymer.     

Preparation and characterization of molecularly imprinted organic–inorganic hybrid materials by sol–gel processing for selective recognition of ibuprofen

This work adopted semi-covalent imprinting to prepare molecularly imprinted polymers (MIP) with ibuprofen, a non-steroidal anti-inflammatory drug, as template by sol–gel processing, which is characterized by both the high affinity of covalent binding and the mild operation conditions of non-covalent rebinding. A functional monomer, which was used to synthesize the monomer-imprinted molecule complex, was prepared by multi-step synthesis for the first time. MIP was characterized by Fourier transform IR spectrum and nitrogen adsorption. Thin-layer chromatography separation was used to evaluate the specific molecular recognition ability of MIP. In addition, dynamic and thermodynamic studies on MIP imprinting ibuprofen were undertaken. The results of equilibrium rebinding experiments showed that MIP exhibited good adsorption capacity for ibuprofen. Scatchard analysis illustrated that the template-polymer system shows only one-site binding behavior with a dissociation constant of 1.84 mmol L^?1. Dynamic adsorption exhibited pseudo-second-order kinetics. The positive value of ΔH^θ and the negative values of ΔG^θ demonstrated that the binding system for MIP is endothermic and spontaneous.     

Preparation of a semicovalent, molecularly surface imprinted polymer for the rapid determination of trace acid orange II in food and environmental samples

In this work, molecularly imprinted polymer (MIP) particles were synthesized using a semicovalent method based on a specific thermally reversible bond, and these particles were used for the rapid detection of the azo dye acid orange II. The imprinted polymers—which were prepared via the covalent reaction of 3-(triethoxysilyl)propyl isocyanate with the template molecules—were attached to the surface of silica-coated magnetic nanoparticles, and a simple thermal reaction was then performed to remove the templates, leaving spaces with specific noncovalent bonds for target re-recognition. The conditions for the synthesis of the MIP were optimized during the polymerization experiments to improve the adsorption capacity and selectivity. The resulting polymers were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy to confirm their structure. The MIPs were subjected to an online solid-phase extraction and a magnetic molecularly imprinted solid-phase extraction procedure. For both methods, all samples were prepared with spiking levels of 5.0, 10.0, and 15.0 μg kg^-1 using high-performance liquid chromatography with UV/vis detection; after the preconcentration of 50-mL sample solutions, the enhancement factors reached 710 and 629. The limits of detection (signal-to-noise ratio of 3) were 9.83 and 17.41 ng L^-1, with relative standard deviations (n?=?9) of 6.72 % and 8.25 %, respectively, for a 4.0 μg L^?1 standard template solution. These two methods were developed to quantify trace acid orange II contents in food and environmental samples; the recoveries ranged from 72 to 105 % and from 70 to 94 %, respectively.     

Preparation and Adsorption Characteristics of Cordycepin Molecularly Imprinted Polymers

The separation of a molecularly imprinted polymer for cordycepin was investigated. The synthesis employed cordycepin as the molecular template, alpha-methylacrylic acid as the functional monomer, glycol dimethyl acrylate as the cross-linking agent, azobisisobutyronitrile as the initiator, and tetrahydrofuran as the solvent and pore-foaming agent. The interaction between cordycepin and the functional monomer was investigated by ultraviolet-visible and infrared spectroscopy. The properties of the molecularly imprinted polymer were analyzed by scanning electron microscopy, equilibrium adsorption experiments, and the Scatchard equation. Static adsorption, solid phase extraction, and high-performance liquid chromatography experiments were employed to evaluate the adsorption properties and selective recognition characteristics. The results showed that the molecularly imprinted polymer had specific adsorption with cordycepin, and the maximum absorption capacity was 1920 µg/g. Scatchard analysis suggested that high affinity and low affinity binding sites were present. For the high affinity case, the dissociation constant and apparent maximum numbers of the binding sites were 0.0089 mmol/L and 4.78 µmol/g, respectively. The dissociation constant and apparent numbers of binding sites were 0.035 mmol/L and 6.047 µmol/g for the low affinity sites. Compared with the corresponding nonimprinted polymer, the cordycepin molecularly imprinted polymer exhibited higher adsorption and selectivity for cordycepin than structural analogs.     

尼卡地平分子聚合物的制备及识别性能研究

采用分子印迹技术合成了以尼卡地平为模板分子,甲基丙烯酸为功能单体的分子印迹聚合物(MIP).运用平衡结合实验研究了聚合物的吸附特性和选择识别能力.通过Scatchard方程分析,结合位点的离解常数Kd=1.03 mmol·L-1,最大表观结合常数Qmax=18.76 μmol·g-1.结果表明,分子印迹聚合物对尼卡地平呈现出较高的吸附性和选择识别性,对尼卡地平药物的分离富集和检测具有实际临床意义.     

A molecularly imprinted polymer for solid phase extraction of allantoin

We describe a molecularly imprinted polymer (MIP) for the solid-phase extraction of the skin protectant allantoin. The MIP was deposited on the surface of monodisperse silica microspheres possessing acroyl groups on the surface (MH-SiO₂). The resulting MIP microspheres (MH-SiO₂@MIP) showed a 3.4-fold higher adsorption capacity and a 1.9-fold better selectivity for allantoin than the respective non-imprinted polymer (MH-SiO₂@NIP). The monolayer adsorption capacities of the MH-SiO₂@MIP and the MH-SiO₂@NIP were calculated with the help of the Langmuir model and found to be 6.8 and 1.9 mg?g^?1, respectively. Adsorption kinetics fit a pseudo-second order rate mechanism, with an initial adsorption rate of 1.44 for the MH-SiO₂@MIP, and of 0.07 mg?g^?1?min^?1 for the MH-SiO₂@NIP. The material can be regenerated, and its adsorption capacity for allantoin remains stable for at least five regeneration cycles. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

Preparation and characterization of protein molecularly imprinted polysiloxane using mesoporous calcium silicate as matrix by sol–gel technology

Calcium silicate particles containing mesoporous SiO₂ on the surface (CaSiO₃@SiO₂) were prepared by acid modification of calcium silicate with diluted hydrochloric acid. Bovine serum albumin (BSA) molecularly imprinted polysiloxane (MIP) was synthesized using silane as the functional monomer, BSA as the template and CaSiO₃@SiO₂ particles as the matrix in an aqueous phase. SEM, granulometry, FT-IR and BET analysis were used to characterize the protein MIP. Influence factors on the rebinding capacity of the MIP were investigated, such as the pH in treating CaSiO₃, eluent type and silane proportion. The mass of BSA loading and rebinding on CaSiO₃@SiO₂ and MIP was investigated. The adsorption and recognition properties of the MIP were evaluated and the results showed that the MIP exhibited an obvious improvement in terms of rebinding capacity for BSA as compared with non-imprinted polysiloxane (NIP). BSA imprinted polysiloxane could recognize the template protein by using Lys, Ova, Hb, and Glo as control proteins, and the selectivity factor (β) was above 2.3. The rebinding capacity of BSA imprinted polysiloxane for BSA reached 81.31 mg/g, which was 2.25 times of NIP.     

Extraction of tributyltin by magnetic molecularly imprinted polymers

We have prepared core-shell magnetic molecularly imprinted polymer nanoparticles for recognition and extraction of tributyl tin (TBT). The use of particles strongly improves the imprinting effect and leads to fast adsorption kinetics and high adsorption capacities. The functional monomer acrylamide was grafted to the surface of Fe₃O₄ nanospheres in two steps, and MIP layers were then formed on the surface by creating a MIP layer on the surface consisting of poly(ethyleneglycol dimethacrylate) with a TBT template. The particles were characterized in terms of morphological, magnetic, adsorption, and recognition properties. We then have developed a method for the extraction of TBT from spiked mussel (Mytilidae), and its determination by liquid chromatography-tandem mass spectrometry. The method has a limit of detection of 1.0 ng?g^?1 (n?=?5) of TBT, with a linear response between 5.0 and 1,000 ng?g^?1. The proposed method was successfully applied to the determination of trace TBT in marine food samples with recoveries in the range of 78.3–95.6 %.

3-氨基苯硼酸为功能单体在壳聚糖上印迹牛血清白蛋白的研究

以壳聚糖为载体, 3-氨基苯硼酸为功能单体对牛血清白蛋白进行了分子印迹的研究, 并对吸附过程进行Langmuir等温吸附模型的数据处理. 结果表明, 印迹聚合物上形成了对于模板分子有较高的吸附容量和选择性的识别位点, Langmuir等温吸附平衡常数为49.5 mL/mg, 结合位点的最大表观结合量为16.3 mg/g, 证明了该印迹聚合物对于牛血红蛋白和溶菌酶这些非模板蛋白的吸附不具有选择性.     

Fluorescent,magnetic dual-responsive molecularly imprinted polymers for the selective detection of moxidectin in animal samples

A simple and effective approach is presented to fabricate fluorescent and magnetic dual-responsive molecularly imprinted polymers for selective recognition of moxidectin. Magnetic gelatin was prepared to provide not only easy magnetic separation, but also significant amino functionalities, allowing surface modification with fluorescein isothiocyanate isomer I and acrylic acid (AA). Based on the double bond provided by AA, molecularly imprinted polymers could be directly coated onto the surface of modified magnetic gelatin. The dual-responsive imprinting polymers feature a high adsorption capacity (87.1 mg g^?1), selective fluorescence response toward moxidectin (imprinting factor = 3.6), rapid magnetic separation, and good reproducibility. Subsequently, the dual-responsive composites were successfully applied as sorbents for selective determination of moxidectin. Upon optimization, a linear range of 10–1000 ng mL^?1 and a detection limit of 6 ng mL^?1 were achieved. The results agree well with those obtained by the classic HPLC–FLD method (r = 0.9935). This developed strategy may find its potential application in rapid, simple, sensitive, and selective determinations of target molecules in complex samples.     

Synthesis,characterization and application of dummy-template molecularly imprinted microspheres for 2,4-d butyl ester

Dummy-template molecularly imprinted microspheres were synthesized via precipitation polymerization employing 2,4-D isooctyl ester as the template molecule instead of 2,4-D butyl ester, while methacrylic acid and divinylbenzene were used as functional monomer and cross-linker in acetonitrile or a mixture of acetonitrile and toluene. The microspheres were characterized by scanning electron microscopy, laser particle size analyzer and fourier transform infrared spectrometry. Binding capacity experiment showed that the molecularly imprinted polymers prepared in a mixture of acetonitrile and toluene had a high binding capacity. The performance of microspheres was further assessed by equilibrium binding and kinetic adsorption experiments. The results showed that the apparent maximum adsorption reached up to 1.35 mg·g^?1 within 10 min. Based on the dummy-template microspheres, a molecularly imprinted solid phase extraction-gas chromatography method was developed for the selective analysis of 2,4-D butyl ester in soil samples. The mean recoveries of 2,4-D butyl ester from blank soil samples ranged from 85.9 to 99.3% with relative standard deviations of 4.5–14.3% (n = 5). The limit of detection and the limit of quantification of 2,4-D butyl ester were 0.8 μg·kg^?1 and 2.3 μg·kg^?1, respectively.     

Recognition of Staphylococcus enterotoxin via molecularly imprinted beads

The synthesis of molecularly imprinted beads for the recognition of the protein Staphylococcus enterotoxin B (SEB) is described. Two kinds of organic silane (3-aminopropyltrimethoxysilane (APTMS) and octyltrimethoxysilane (OTMS)) were polymerized on the surface of polystyrene microspheres after the SEB template was covalently immobilized by forming imine bonds. The resulting imprinted beads were selective for SEB. The Langmuir adsorption models were applied to describe the equilibrium isotherms. The results showed that an equal class of adsorption was formed in the molecularly imprinted polymer (MIP) with the maximum adsorption capacity of 3.86 mg SEB/g imprinted beads. The MIP has much higher adsorption capacity for SEB than the nonimprinted polymer, and the MIP beads have a higher selectivity for the template molecule.     

Novel molecularly imprinted polymeric microspheres for preconcentration and preservation of polycyclic aromatic hydrocarbons from environmental samples

Molecularly imprinted polymer (MIP) microspheres with diameters in the range 60–500 μm were synthesized in a continuous segmented flow microfluidic reactor and used as packing material for microtraps for the selective separation of benzo[a]pyrene (BAP) from environmental aqueous samples. The synthesis involved the pumping of monodisperse droplets of acetonitrile containing methacrylic acid as the functional monomer, BAP as a template, and ethylene glycol dimethacrylate as the cross-linking monomer into the microchannels of the microfluidic reactor. The microspheres showed high adsorption capacity and selectivity for BAP in aqueous solutions; both are important for the environmental monitoring and analysis of BAP. The adsorption capacity for BAP of the smallest MIP microspheres (size range 60–80 μm), prepared as part of this study, was 75 mg g^-1 in aqueous solutions; furthermore, this adsorption capacity was close to 300 % higher than that of commercially used activated carbon. Microtraps packed with MIP retained BAP intact for at least 30 days, whereas microtraps packed with activated carbon for BAP showed 40 % reduction in BAP concentration for the same period. This study has demonstrated that MIP microtraps have significant potential for the selective enrichment and preservation of targeted polycyclic aromatic hydrocarbons from complex environmental samples.     

核-壳型赤藓红分子印迹聚合物的制备及吸附性能的评价

以氨基化修饰的SiO_2为内核,人工合成色素赤藓红为模板,甲醇/水为溶剂,4-乙烯基吡啶为功能单体,二甲基丙烯酸乙二醇酯为交联剂,偶氮二异丁腈为引发剂,采用表面印迹技术,制备核-壳型赤藓红分子印迹聚合物。通过红外光谱对其结构进行表征,并通过动力学吸附、等温饱和吸附和实际样品加标实验对其吸附性能进行评价。结果表明,核-壳型赤藓红分子印迹聚合物具有较快的吸附能力,在15min左右达到吸附平衡,有较好的吸附容量,能够从复杂的食品样品中选择性吸附模板,且回收可达85%。     

Preparation and Adsorption Ability of Molecularly Imprinted Polymer Microspheres for Malachite Green

Molecularly imprinted polymer (MIP) microspheres were synthesized through precipitation polymerization using malachite green (MG) as template, methacrylic acid (MAA) as monomer, and trimethylolpropane trimethacrylate (TRIM) as cross-linker. The microsphere structure of MIP was characterized by IR spectroscopy and SEM. The influence of preparation conditions such as monomer and cross-linker dosages on the polymer absorption of MG in acetonitrile solution was also explored. Under the optimum synthesis conditions (0.25 mmol MG, 1.5 mmol MAA, 2.5 mmol TRIM, 40 mL acetonitrile), the prepared MIP microspheres have a binding capacity as high as 2000 µg g^?1 of MG with an imprinting factor of above 4.0. The result suggests that the prepared MIP microspheres are promising material for the selective extraction of MG in complicated matrix solutions.     

Molecularly imprinted polymer for metsulfuron-methyl and its binding characteristics for sulfonylurea herbicides

A molecularly imprinted polymer (MIP) was prepared using metsulfuron-methyl (MSM) as the template molecule. A combinatorial protocol has been employed to optimize the polymer in terms of the kind and relative amounts of functional and cross-linking monomers. A copolymer of 2-(trifluoromethyl)acrylic acid (TFMAA) and divinylbenzene (DVB) showed the highest binding capacity for MSM. The binding characteristics of the imprinted polymers and MSM were evaluated in various solvents using equilibrium binding experiments. The results showed that the MIP binds MSM only in dichloromethane, which was used as the porogen during polymerization. Scatchard plot analysis revealed that two classes of binding sites were formed in the imprinted polymer with dissociation constants of 32.3 μmol l⁻¹ and 1.7 mmol l⁻¹, respectively. The specificity of the imprinted polymer was investigated by binding assays using MSM and other structurally related sulfonylurea herbicides. The results indicated that the imprinted polymer showed a marked selectivity for MSM.     

Preparation of MIP grafts for quercetin by tandem aryl diazonium surface chemistry and photopolymerization

The food antioxidant quercetin was used as a template in an ultrathin molecularly imprinted polymer (MIP) film prepared by photopolymerization. Indium tin oxide (ITO) plates were electrografted with aryl layers via a diazonium salt precursor bearing two terminal hydroxyethyl groups. The latter act as hydrogen donors for the photosensitizer isopropylthioxanthone and enabled the preparation of MIP grafts through radical photopolymerization of methacrylic acid (the functional monomer) and ethylene glycol dimethacrylate (the crosslinker) in the presence of quercetin (the template) on the ITO. The template was extracted, and the remaining ITO electrode used for the amperometric determination of quercetin at a working potential of 0.26 V (vs. SCE). The analytical range is from 5.10^?8 to 10^?4 mol L^?1, and the detection limit is 5.10^?8 mol L^?1.

Efficient Separation and Purification of Epigallocatechin Gallate (EGCG) Based on EGCG-Imprinted Polymer Prepared with Chitosan as Matrix

A molecularly imprinted polymer (MIP), which was suitable for recognizing epigallocatechin gallate (EGCG), was prepared by using EGCG as template molecule and biocompatible chitosan as a functional matrix in aqueous medium. Molecular recognition ability of the EGCG-imprinted polymer (EIP) was evaluated by high performance liquid chromatography (HPLC). The results show that the EIP has a high imprinting factor (1.32) for EGCG and was used to purify EGCG from crude tea polyphenol efficiently. The percentage of EGCG can be improved from 78.6% in crude tea polyphenol (TP) to 90.1% in product and the adsorption quantity per unit can reach 4.02 mg · g^?1. EIP shows potential excellent prospect in the application of separating and purifying EGCG from TP.     

Super-Paramagnetic Nanoparticles by Surface Imprinting on Graphene Oxide Modified Iron (II,III) with Application for the Determination of Ovalbumin by Absorption Spectroscopy

Protein surface imprinting produces materials capable of selective recognition and capture of proteins. Herein, a protein surface imprinted polymer on graphene oxide modified super-paramagnetic Fe₃O₄ nanoparticles is reported. The molecularly imprinted polymer was synthesized by ultrasound-assisted suspension polymerization, using ovalbumin as the template molecule, 3-aminophenylboronie acid as the functional monomer, and methylene-bis-acrylamide as the cross-linking agent. The nanoparticles were approximately 40 nanometers in size and super-paramagnetic. Moreover, these particles demonstrated considerably high adsorption capacity, fast adsorption kinetics, and selective binding affinities toward the template protein ovalbumin. The calibration curve of ovalbumin was linear from 5.0 × 10^?11 to 1.0 × 10^?10 molar. The limit of detection of ovalbumin was 2.0 × 10^?11 M. These results show that this super-paramagnetic material has potential for biological macromolecule separation and determination.     

Evaluation of a molecularly imprinted polymer for the isolation/enrichment of β-estradiol

The selective preconcentration of estradiol was explored using the recognition ability of a molecularly imprinted polymer (MIP) in the solid phase extraction (SPE) format. Polymeric particles were imprinted with 17β-estradiol using methacrylic acid as functional monomer and divinylbenzene as crosslinker. Binding studies of these polymeric particles towards 17β-estradiol showed selectivity over non-imprinted polymers, using acetonitrile as solvent. The imprinted polymer showed a recovery of 88% for β-estradiol in deionized water and 81% in surface water. The selectivity of the MIP over the non-imprinted polymer was relatively low, only 10% higher recovery. The results indicate that the MIP imprinted with 17β-estradiol does not appear to provide a viable approach to be used in a sample clean-up or enrichment step for the determination of estradiol in aqueous systems.