Molecularly Imprinted Membranes with Affinity Properties for Folic Acid

The extraction of folic acid from aqueous solutions was proposed through a novel procedure based on the membrane separation process using the approach of molecular imprinting. Molecularly imprinted membranes were prepared via the phase inversion technique using poly(acrylonitrile-co-acrylamide) copolymer as the membrane material and folic acid as the template molecule. Poly(acrylonitrile)-based membranes were also prepared as the reference material. Polymer composition, membrane preparation method, and the pH used in the binding experiments were the parameters which mostly influenced the recognition properties of the imprinted membranes. In particular, the solvent evaporation method allowed to obtain poly(acrylonitrile-co-acrylamide) imprinted membranes which at pH 5.0 showed a specific binding capacity of 5.3 µmol/g_memb. Corresponding blank membranes (prepared in absence of the template molecule), only showed a poor non-specific binding of 1.0 µmol/g_memb. Polyacrylonitrile-based membranes showed lower folic acid retention (1.5 µmol/g_memb. when prepared in the presence of the template and 0.9 µmol/g_memb. when prepared in the absence of the template).     

3,5,7,3＇,4＇,5＇-六羟基黄酮分子印迹聚合物制备及性能表征

采用分子印迹技术合成了对3,5,7,3＇,4＇,5＇-六羟基黄酮具有高效选择性的分子印迹聚合物,通过静态吸附的方法,利用Scatchard模型,研究了分子印迹聚合物的特异性识别能力。实验表明,以甲基丙烯酸为功能单体,在甲苯溶剂中聚合得到的分子印迹聚合物对3,5,7,3＇,4＇,5＇-六羟基黄酮具有较大的吸附富集能力和识别特性。其饱和吸附容量达到30.8 mg/g。     

Computer simulation and preparation of molecularly imprinted polymer membranes with chlorogenic acid as template

A computational approach was developed for screening functional monomers for rational design of molecularly imprinted polymer (MIP) membranes. It was based on a comparison of the binding energy of complexes between a template and various functional monomers. According to the results of theoretical calculations, MIP membranes with chlorogenic acid as a template were prepared with a UV irradiation polymerization method, using 4‐vinylpyridine as a functional monomer and N,N′‐methylenebisacrylamide as a crosslinker, with poly(vinylidene fluoride) microfiltration membranes as the support. Membranes covered with a thin layer of imprinted polymer selective to chlorogenic acid were then obtained and tested using the equilibrium‐adsorption method. The high affinity of these synthetic membranes to chlorogenic acid, together with their straightforward and inexpensive preparation, provides a good basis for the development of applications of imprinted polymers in separation processes such as solid‐phase extraction. Copyright © 2011 Society of Chemical Industry     

Molecularly imprinted poly(MAA‐co‐AM) composite membranes for selective recognition of nicosulfuron herbicide

Molecularly imprinted membranes with different ratio of acrylamide (AM) versus methacrylic acid (MAA) were prepared by photocopolymerization on commercial filter paper using nicosulfuron as the template. The structures, the thermal stability, and the morphology of membranes were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. Static equilibrium binding and competitive recognition properties of the membranes to nicosulfuron and its analogs (pyrazosulfuron ethyl and bensulfuron methyl) were tested. The results showed that nicosulfuron‐imprinted membranes had the best recognition capacity to nicosulfuron compared with its analogs. The biggest selectivity factors of ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm P}_{\rm 2} }$ and ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm B}_{\rm 3} }$ were 1.28 and 1.83 and the imprinted factor reached to 2.34. The results of this study implied that the molecularly imprinted composite membranes could be used as separation membranes for nicosulfuron enrichment. The Scatchard plot revealed that one class of binding sites was mainly produced in the imprinted composite membrane in the studied concentration range of nicosulfuron. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparison of molecular adsorption ability of the molecularly imprinted polymers prepared by ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate as cross linkers

The target of this study was to synthesize the molecularly imprinted polymers (MIPs) of L ‐phenylalanine as the solid phases for characterization of molecular adsorption by molecularly imprinted solid phase extraction (MISPE). These MIPs, in microscale, were synthesized using thermal (40°C)‐compared with thermal (65°C)‐initiated polymerization process. Itaconic acid was chosen as the functional monomers, and either ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate (TRIM) was used as the cross linker and was compared together. The influences of several parameters on the properties of the MIPs were investigated, especially physical robustness from the percentage yields and molecular adsorption from the percentage recovery by MISPE. The best yields were obtained from polymers made using TRIM and thermal (65°C)‐initiated polymerization. However, there were no significant differences in molecular adsorption. It was concluded that these parameters can be considered to synthesize MIPs for chiral separation in advance steps such as other related chromatographic techniques. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2325–2330, 2007     

Synthesis and Evaluation of a Molecularly Imprinted Polymer for Solid Phase Extraction of Ethopabate from Chicken Tissue

In this paper the development and evaluation of a molecularly imprinted polymer (MIP) for ethopabate is described. Ethopabate (ETP), 4-acetamido-2-ethoxybenzoic acid methyl ester, is one of the antibiotics which is used as coccidiostat in poultry feeds. In the present study, two widely used functional monomers, methacrylic acid (MAA) and 4-vinylpyridine (4-VP) were compared theoretically and experimentally as the candidates for MIP preparation. Hyperchem software was employed to estimate binding energies between ETP and functional monomers and batch rebinding experiments were performed to study the binding characteristics of the polymers. The results showed that MAA is a better functional monomer to prepare MIP. UV/Vis and NMR spectroscopy were used as two common tools to study the interactions between ETP and MAA in the pre-polymerization mixture. Liquid chromatography experiments showed that the prepared MIP has recognition capability toward ETP in comparison with other structurally related compounds. The ETP-imprinted polymer was further applied for selective solid phase extraction (SPE) of ETP from a chicken tissue sample. The extraction yield of ETP was found to be quantitative (87 ± 3%) and the LOD and LOQ based on 3 and 10 times of the noise of HPLC profile were 0.05 and 0.32 ng ml^?1, respectively. It was confirmed that the binding ability of the prepared MIP for ETP was essentially sufficient in the presence of other compounds coexisting in tissue sample. Therefore, as a selective and efficient solid phase material, ETP-imprinted polymer has a high potential application in the analysis of residues of this antibiotic in chicken tissue samples.     

Molecularly Imprinted Polymers Based on Chitosan for 2,4-Dichlorophenoxyacetic Acid Removal

The development of low-cost and eco-friendly materials for the removal of pollutants from water is one of the main modern challenges. For this purpose, molecularly imprinted polymers were prepared under optimized conditions starting from chitosan (CS), chemically or ionically modified with glycidyl methacrylate (GMA) or itaconic acid (ITA), respectively. 2,4-Dichlorophenoxyacetic acid (2,4-D) was used as a template, obtaining the CS_GMA and CS_ITA series. The influence of the template concentration on the MIPs’ (molecularly imprinted polymers) morphology, thermal behaviour and swelling ability, as well as on the 2,4-D removal capacity, were analyzed. The amount of the template used for the imprinting, together with the different permeability of the matrices, were the key factors driving the analyte uptake process. Despite the good performance shown by the non-imprinted CS_GMA sample, the best results were obtained when CS_GMA was imprinted with the highest amount (5%) of template (CS_GMA_5). This system was also more efficient when consecutive adsorption experiments were carried out. In addition, CS_GMA_5 had a desorption efficiency of 90–100% when a low pesticide concentration was used. These findings suggest that the presence of imprinted cavities could be useful in improving the performance of sorbent materials making CS_GMA_5 a possible candidate for 2,4-D removal.     

Molecularly imprinted polymer microspheres with nanopore cavities prepared by precipitation polymerization as new carriers for the sustained release of dipyridamole

Imprinted polymers are now being increasingly considered for active biomedical uses such as drug delivery. In this work, the use of molecularly imprinted polymers (MIPs) in designing new drug delivery devices was studied. Imprinted polymers were prepared from methacrylic acid (MAA) (functional monomer), ethylene glycol dimethacrylate (cross‐linker), and dipyridamole (DIP) (as a drug template) using precipitation polymerization method. The influence of the template/functional monomer proportion and pH on the achievement of MIPs with nanopore cavities with a high enough affinity for the drug was investigated. The small pores (average 3.9 nm) in the imprinted microspheres show excellent retention properties for the target analyte. The polymeric devices were further characterized by FT‐IR, thermogravimetric analysis, scanning electron microscopy, photon correlation spectroscopy, Brunauer‐Emmett‐Teller analysis, and binding experiments. The imprinted polymers showed a higher affinity for DIP and a slower release rate than the nonimprinted polymers. The controlled releases of DIP from the prepared imprinted polymers were investigated by an in vitro dissolution test by measuring the absorbance at 284 nm by means of a UV–Visible spectrophotometer. Loaded imprinted microsphers showed very slow release in various solutions such as phosphate buffer solution (pH 6.8), HCl (pH 1.0) and mixture of HCl and MeOH at 37.0 ± 0.5°C and were able to prolong DIP release for more than two days. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

焦性没食子酸分子印迹聚合物的制备与吸附特征研究

以焦性没食子酸为模板分子,丙烯酸为功能单体,甲醇为溶剂,研究了模板分子与功能单体的结合比例,表明焦性没食子酸和丙烯酸之间通过氢键形成1∶1型配合物。在模板分子与功能单体、交联剂物质的量的比为1∶4∶20的条件下,采用沉淀聚合法制备了焦性没食子酸分子印迹聚合物微球。静态吸附实验表明,可制备出吸附量大且特异性识别能力较高的分子印迹聚合物,对焦性没食子酸有较高的亲和性和选择性。采用恒温振荡平衡吸附法以及Scatchard分析研究了聚合物的吸附特征,结果表明焦性没食子酸分子印迹聚合物在水环境下存在2种吸附位点,最大表观吸附量分别为7.5516μg/mg和11.9225μg/mg,平衡离解常数分别为9.2720×10-3mmol/L和0.1892 mmol/L。     

Ultrasonic-assisted solid-phase extraction of sotalol in human urine samples using molecularly imprinted nanoparticles: Experimental design and adsorption study

ABSTRACT

Ultrasonic-assisted solid-phase extraction via molecularly imprinted nanoparticles followed by HPLC-UV was used for trace determination of sotalol. Under optimized conditions, linear range, limit of detection, and limit of quantification of the proposed method were found to be 20–2000, 7.8, and 24 ng/mL, respectively. The adsorption capacity of sotalol for molecularly imprinted nanoparticles and non-imprinted nanoparticles was determined from the derived Langmuir isotherm and was found to be 31.55 and 15.22 mg/g, respectively. The proposed method was used for the separation of trace amounts of sotalol in human urine samples with acceptable high recoveries more than 94.40% and the inter-day precision with the coefficient of variation lower than 5%.     

Molecular Imprinted Solid-Phase Extraction System for the Selective Separation of Oleuropein from Olive Leaf

Oleuropein has many antimicrobial, antiviral, and anticancer features found in olive leaf. Therefore, its isolation from olive leaf is very important in such kinds of applications. In this study, a solid-phase extraction system based on the molecularly imprinted polymer (MIP) was proposed for the selective separation of oleuropein from olive leaf. First, oleuropein imprinted polymer has been prepared by the suspension polymerization using methacrylolamidoantiprine–iron (III) metal-chelate monomers. After that, the oleuropein adsorption capacity and selectivity of the prepared imprinted polymer has been determined. The maximum adsorption capacity of oleuropein has found to be 140 mg g^?1. Finally, MIP has been used as a sorbent in the solid-phase extraction for the separation of oleuropein from crude extract of olive leaves. The oleuropein analyses have been realized by high performance liquid chromatography. The obtained results indicated that the prepared molecularly imprinted sorbent could be used for at least 10 times for purification of oleuropein from olive leaf. The application of the proposed system in the real sample showed that 24.2 mg pure oleuropein could be obtained from 1.0 g of crude olive leaf extract. As a result, the low cost, simple, and selective adsorbent has been developed for oleuropein adsorption. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

Preparation and characterization of metal-complex imprinted PVDF hollow fiber membranes

Using nickel-2,2′-dipyridyl complex as a template, N-vinyl-2-pyrrolidone as the metal coordination functional monomer, and ethylene glycol dimethacrylate as the crosslinker, polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membrane as the supported membrane, metal complex imprinted polymeric membranes were prepared. The association constant of template-monomer interaction in the prepolymerization solution was estimated to be 4.38 × 10⁴ (L/mol)² by spectrophotometric titration analysis. The attenuated total reflection Fourier transform infrared spectroscopy and scanning electron micrograph characterization indicated that the surface of the support PVDF membrane was completely coated by the imprinted polymer layer after modification. The imprinted membranes exhibited the selective permeability for the template in certain nickel acetate solution. The molecularly imprinted membranes gave higher permeation separation factors at about pH 6, whereas increasing pressure would lower the separation ability. The effects of ion concentration, cations and counterions, ligand selectivity, pH, and trans-membrane pressure were investigated and the permeation performances of the imprinted membranes could be regarded as facilitated transport mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Transport selectivity of tribenuron‐methyl imprinted polymer nanowire membrane prepared using N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer

Using tribenuron‐methyl as a template and N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer, a molecularly imprinted nanowire membrane was prepared over an anodic alumina oxide membrane. The nanowire fabric of the imprinted membrane was established with a scanning electron microscope and a transmission electron microscope. However, the nonimprinted particulate membrane is formed in the absence of a template. Scatchard analysis showed that an equal class of binding sites were formed in the imprinted nanowire membrane and the dissociation constant and the maximum number of these binding sites were estimated to be 1.44 × 10⁻⁵ M and 22.7 µmol/g, respectively. The permeation experiments throughout the imprinted membrane and the nonimprinted one were carried out in a solution containing the template and its competitive analogs. These results demonstrated that the molecularly imprinted nanowire membrane exhibited higher transport selectivity for the template tribenuron‐methyl than its analogs, chlorimuron‐ethyl, thifensulfuron‐methyl and N‐(4‐bromophenylcarbamoyl)‐5‐chloro‐1H‐benzo[d]imidazole‐2‐carboxamide. But the nonimprinted granular membrane had no permselectivity for the four substrates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

不同功能单体制备的S-萘普生印迹聚合物材料的性能

以S-萘普生为模板,分别采用丙烯酰胺(AM)、N-乙烯基吡咯烷酮(NVP)和甲基丙烯酸(MAA)3种功能单体,合成了印迹聚合物P1、P2和P3。用UV和Chem 3D计算模拟,研究了功能单体与模板分子之间的相互作用,经PM3半经验方法计算得到AM、NVP、MAA与模板分子之间的相互作用能分别为-32.06、-21.01和-1.55kJ/mol。平衡结合实验测得当底物浓度为0.1 mmol/L时,P1、P2和P3的吸附量分别为0.360、0.305和0.150μmol;在浓度为0.1~4 mmol/L时,3种分子印迹聚合物对S-萘普生的吸附量大小关系为P1>P2>P3,这与计算出的功能单体与模板分子之间的相互作用能大小关系一致。     

Application of Molecularly Imprinted Polymer for Extraction and Determination of Nalidixic Acid by High-Performance Liquid Chromatography

Nalidixic acid imprinted polymer has high application potential in clinical purposes. Molecularly imprinted polymers were prepared using nalidixic acid as the template molecule. The polymer was synthesized in a non-covalent approach with N,N-dimethylacrilamid and allyl glycidyl ether/iminodiacetic acid as the functional monomer. The effects of various parameters such as pH and adsorption time on adsorption capacity were considered. It was confirmed that the binding ability of the prepared molecularly imprinted polymer for nalidixic acid was essentially sufficient in the presence of the other compounds coexisting in human urine.     

Synthesis of highly selective spherical caffeine imprinted polymers via ultrasound‐assisted precipitation polymerization

A facile and efficient method for synthesis of molecularly imprinted polymers via ultrasound‐assisted precipitation polymerization was developed. Caffeine was applied as a model template in the imprinting using methacrylic acid and ethylene glycol dimethacrylate as a functional monomer and a crosslinker, respectively. Polymerization under sonochemical conditions proceeded rapidly (within 3 h at 60°C) to afford polymer microspheres with narrow size distributions in excellent yields while maintaining the binding specificity toward the template. It was found that the imprinted polymer prepared at low initial temperature (40°C) exhibited the best caffeine binding performance in terms of specificity and selectivity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Exploiting β-Cyclodextrin in Molecular Imprinting for Achieving Recognition of Benzylparaben in Aqueous Media

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP.     

硅胶表面罗红霉素分子印迹聚合物的制备及选择性吸附性能

以γ-氨丙基三甲氧基硅烷(AMPS)为硅胶表面改性剂,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,罗红霉素(ROX)为模板分子,制备得到罗红霉素分子印迹硅胶材料(ROX-MIP-PMAA/SiO₂),采用红外、扫描电镜和粒径测定等方法对其进行了表征.通过静态和动态吸附实验研究了ROX-MIP-PMAA/SiO₂对罗红霉素的吸附性能,并以红霉素为竞争底物,研究其选择吸附性能.结果显示,ROX-MIP-PMAA/SiO₂对罗红霉素的吸附能力明显大于非印迹硅胶(NIP-PMAA/SiO₂),其对罗红霉素和红霉素的分离因子为1.21,说明其对罗红霉素具有较好的选择吸附性能.     

丙烯酰胺为功能单体制水杨酸分子印迹聚合物

1HNMR实验表明,在弱极性溶剂中,水杨酸与丙烯酰胺之间的氢键作用大于水杨酸与α-甲基丙烯酸之间的氢键作用。据此以丙烯酰胺为功能单体、二甲基丙烯酸乙二醇酯为交联剂,合成了水杨酸分子印迹聚合物。电镜和静态吸附实验表明,选用乙腈做溶剂合成的印迹聚合物疏松多孔、吸附性能较好,而用氯仿做溶剂合成的印迹聚合物致密、吸附性能较差。以丙烯酰胺为功能单体合成的水杨酸分子印迹聚合物分离因子α=7.2,印迹效率因子β=5.1;而以α-甲基丙烯酸为功能单体合成的水杨酸分子印迹聚合物分离因子α=1.7,印迹效率因子β=2.1。     

2,4-Dichlorophenol molecularly imprinted two-dimensional photonic crystal hydrogels

A novel molecularly imprinted two-dimensional (2-D) photonic crystal hydrogels (MIPH) for sensitive and label-free recognition of 2,4-dichlorophenol (2,4-DCP) was prepared. The 2-D photonic crystal template was fabricated by using air-water interface self-assembly method. And then the template was embedded with molecularly imprinted polymer, which was synthesized with 2,4-DCP as imprinted molecules, dimethyl sulfoxide as solvent, acrylic acid and acrylamide as functional monomers, N,N-methylene bis acrylamide as cross-linker, azobisisobutyronitrile as initiator. The imprinted molecules were removed by 0.01 M ammonia solution. The results indicated that the 2,4-DCP molecularly imprinted 2-D photonic crystal hydrogels has good response and recognition ability to 2,4-DCP. When the molar ratio of cross-linking density of MIPH is 2.3% and the molar ratio of imprinting molecule is 5.0%, the change of Debye ring diameter is the largest. The diameter of Debye ring increased by 7.1 mm when the concentration of 2,4-DCP changed from 0 to 1 × 10⁻⁶ M, and the particle spacing of MIPH reduced 38 nm. In addition, the diameter of the Debye ring hardly changed in the solution of analogues of 2,4-DCP such as, phenol, 2-chlorophenol, 2,4,6-trichlorophenol and so on, indicating that the MIPH has highly sensitivity and specificity.