Molecularly imprinted cryogel cartridges for the selective recognition of tyrosine

Molecularly imprinted polymers are used for creating a specific cavity and selective recognition sites for the structure of a target molecule in a polymeric structure. In this study, specific molecularly imprinted cryogel cartridges were synthesized using two distinct functional monomers to compare imprinting efficiency for the selective recognition of Tyrosine (Tyr). Tyr-imprinted cryogel cartridge (MIP1) was prepared using metal-chelate coordination for the imprinting process by free-radical bulk polymerization under frozen conditions, and Tyr-imprinted cryogel cartridge (MIP2) was prepared in the same way using hydrophobic effects for imprinting. After the characterization of the cryogel cartridges was carried out, the optimum adsorption conditions of both were determined according to the different parameters such as flow rate (0.5–2.5 ml/min), pH of the medium (4.0–8.0), initial Tyr concentration (0.1–3.0 mg/ml), and temperature (4–45°C). Selectivity experiments of Tyr-imprinted and non-imprinted cryogel cartridges were carried out by using phenylalanine, tryptophan, and cysteine. Besides, the eluted Tyr from MIP1 and MIP2 cryogel cartridge were applied to FPLC system. Also, the reusability experiments of Tyr-imprinted cryogel cartridges was observed no significant decrease in the adsorption capacity.     

Applications of magnetic surface imprinted materials for solid phase extraction of levofloxacin in serum samples

In this work, molecularly imprinted magnetic carbon nanotubes (MCNTs@MIPs) was prepared with surface imprinting technique for extraction of levofloxacin in serum samples. The preparation of molecularly imprinted polymers (MIPs) used levofloxacin as template, methacrylic acid as functional monomer, and ethylene glycol dimethacrylate as cross‐linker, and the magnetic carbon nanotubes (MCNTs) was synthesized by solvothermal method. The prepared polymers not only can be separated and collected easily by an external magnetic, but also exhibited high specific surface area and high selectivity to template molecules. Kinetic adsorption and static adsorption capacity investigations indicated that the synthesized MCNTs@MIPs had excellent recognition towards levofloxacin. Furthermore, magnetic solid phase extraction (MSPE) using the prepared MCNTs@MIPs as sorbent was then investigated, and an efficient sample cleanup was obtained with recoveries ranged from 78.7 ± 4.8 % to 83.4 ± 4.1%. In addition, several parameters, including the pH of samples, the amount of MCNTs@MIPs, the adsorption and desorption times, and the eluent, were investigated to obtain optimal extraction efficiency. Under the optimal extraction conditions, the stability of the polymer was also evaluated, and the average recovery reduced less than 7.6% after 5 cycles. MCNTs@MIPs successfully applied in the preconcentration and determination of levofloxacin in serum sample suggested that the MSPE method based on the novel polymers could be a promising alternative for selective and efficient extraction of trace amounts of pharmaceutical substances in bio‐matrix samples. Copyright © 2015 John Wiley & Sons, Ltd.     

超声波辅助抽提法在孔雀石绿分子印迹固相萃取中的应用

采用沉淀聚合法制备孔雀石绿分子印迹聚合物(MG-MIPs),以洗脱效率及吸附量为指标,考察超声波辅助抽提法对MIPs中MG洗脱效果及吸附性能的影响,通过扫描电镜观察MIPs的表面形态,并对其吸附性能进行研究。结果表明:模板分子MG在超声30 min、超声10次、料液比m(MG-MIPs)∶V(甲醇-乙酸溶液)为1∶10(g/m L)、温度为25℃、超声功率为270 W的条件下,洗脱效果最好,MIPs在固相萃取柱中的吸附效率较高,达到198μg/g。     

Characterization of molecularly imprinted polymer nanoparticles by photon correlation spectroscopy

We follow template‐binding induced aggregation of nanoparticles enantioselectively imprinted against (S)‐propranolol, and the non‐imprinted ones, using photon correlation spectroscopy (dynamic light scattering). The method requires no separation steps. We have characterized binding of (R,S)‐propranolol to the imprinted polymers and determined the degree of non‐specificity by comparing the specific binding with the results obtained using non‐imprinted nanoparticles. Using (S)‐propranolol as a template for binding to (S)‐imprinted nanoparticle, and (R)‐propranolol as a non‐specific control, we have determined range of concentrations where chiral recognition can be observed. By studying aggregation induced by three analytes related to propranolol, atenolol, betaxolol, and 1‐amino‐3‐(naphthalen‐1‐yloxy)propan‐2‐ol, we were able to determine which parts of the template are involved in the specific binding, discuss several details of specific adsorption, and the structure of the imprinted site. Copyright © 2014 John Wiley & Sons, Ltd.     

Design and synthesis of molecularly imprinted polypyrrole based on nanoreactor SBA-15 for recognition of ascorbic acid

Molecular imprinting is an attractive technique for preparing mimics of natural and biological receptors. Nevertheless, molecular imprinting for aqueous systems remains a challenge due to the hydrogen bonding between templates and functional monomers destroyed in the bulk water. The hydrogen bonding between templates and monomers are the most crucial factor governing recognition, particularly in non-covalent molecularly imprinted polymers. Using mesoporous materials for molecular imprinting is an effective approach to overcome this barrier and to remove the limitations of the traditional molecularly imprinted polymers which include incomplete template removal, small binding capacity, slow mass transfer, and irregular materials shape. Here, SBA-15 was used as a mesoporous silica material for synthesis of molecularly imprinted polypyrrole. The pyrrole monomers and template molecules were immobilized onto the SBA-15 hexagonal channels, and then polymerization occurred. The resulting nanocomposites were characterized by Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. In batch rebinding tests, the imprinted nanocomposites reached saturated adsorption within 100min and exhibited significant specific recognition toward the ascorbic acid (AA) with high adsorption capacity (83.7mgg(-1)). To further illustrate the recognition property of the imprinted nanocomposites, binary competitive and non-competitive adsorption experiments were performed with ascorbic acid, dopamine, paracetamol and epinephrine. The imprinting factors for these compounds in non-competitive adsorption experiments were 3.2, 1.5, 1.4 and 1.3, respectively. The results showed that the imprinted nanocomposites exhibited significant adsorption selectivity for the ascorbic acid against the related compounds.     

Epitope imprinting of iron binding protein of Neisseria meningitidis bacteria through multiple monomers imprinting approach

Epitope imprinting is a promising technique for fabrication of novel diagnostic tools. In this study, an epitope imprinted methodology for recognition of target epitope sequence as well as targeted protein infused by bacterial infection in blood samples of patients suffering from brain fever is developed. Template sequence chosen is a ferric iron binding fbp A protein present in Neisseria meningitidis bacteria. To orient the imprinting template peptide sequence on gold surface of electrochemical quartz crystal microbalance (EQCM), thiol chemistry was utilized to form the self‐assembled monolayer on EQCM electrode. Here, synergistic effects induced by various noncovalent interactions extended by multiple monomers (3‐sulfopropyl methacrylate potassium‐salt and benzyl methacrylate) were used in fabricating the imprinting polymeric matrix with additional firmness provided by N,N‐methylene‐bis‐acrylamide as cross‐linker and azo‐isobutyronitrile as initiator. Extraction of template molecule was carried out with phosphate buffer solution. After extraction of epitope molecules from the polymeric film, epitope molecularly imprinted polymeric films were fabricated on EQCM electrode surface. Nonimprinted polymers were also synthesized in the similar manner without epitope molecule. Detection limit of epitope molecularly imprinted polymers and imprinting factor (epitope molecularly imprinted polymers/nonimprinted polymers) was calculated 1.39 ng mL^?1 and 12.27 respectively showing high binding capacity and specific recognition behavior toward template molecule. Simplicity of present method would put forward a fast, facile, cost‐effective diagnostic tool for mass health care.     

硝酸铵水凝胶分子印迹聚合物的制备

目的：目前安全问题成为世界各国的首要问题,尤其是对炸药分子的检测。硝酸铵是硝铵炸药的主要成分。研究水凝胶分子印迹法对硝铵炸药分子的检测。方法：水凝胶分子印迹方法制备硝酸铵水凝胶分子印迹聚合物,运用静态结合实验对其结合率进行了测定。结果：聚合物对硝酸铵具有良好的识别和吸附性能。印迹聚合物的解离常数为4.08g/L,最大吸附量为3.51mg/g。结论：水凝胶分子印迹法可合成水溶性炸药分子印迹聚合物,并且识别及吸附性能良好。     

Preparation of molecularly imprinted polymers for artemisinin based on the surfaces of silica gel

Artemisinin is an effective antimalarial drug isolated from the herbal medicine Artemisia annua L. Molecular imprinting is a technique of preparing molecularly imprinted polymers (MIPs) which can specifically recognize the imprinted template molecules. In this work, silica gel were used as supporting matrix, and vinyltriethoxysilane (VTES) was grafted onto its surface. The preparation of MIPs for artemisinin was performed on the surfaces of the modified silica gel using artemisinin as the template, acrylamide (AM) and methacrylic acid (MAA) as the functional monomers, ethylene glycol dimethacrylate (EGDMA) as the cross-linker and 2,2'-azo-bis-isobutyronitrile (AIBN) as the initiator. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and pore size analysis were used to characterize the prepared MIPs. The adsorption kinetic curve, adsorption isotherm and selective adsorption were measured by static method. The adsorption reached equilibrium at about 10 h, while fast adsorption took place during the first 2-3 h. The maximum adsorption capacity has been found to be 37.13 mg/g according to calculation with Langmuir-Freundlich isotherm. The electivity coefficients of MIPs for artemisinin with respect to artemether and arteether were 2.88 and 3.38, respectively. The results showed that the MIPs possessed good specific adsorption capacity and selectivity for artemisinin.     

Mechanisms underlying molecularly imprinted polymer molecular memory and the role of crosslinker: resolving debate on the nature of template recognition in phenylalanine anilide imprinted polymers

A series of molecular dynamics simulations of prepolymerization mixtures for phenylalanine anilide imprinted co-(ethylene glycol dimethacrylate-methacrylic acid) molecularly imprinted polymers have been employed to investigate the mechanistic basis for template selective recognition in these systems. This has provided new insights on the mechanisms underlying template recognition, in particular the significant role played by the crosslinking agent. Importantly, the study supports the occurrence of template self-association events that allows us to resolve debate between the two previously proposed models used to explain this system's underlying recognition mechanisms. Moreover, the complexity of the molecular level events underlying template complexation is highlighted by this study, a factor that should be considered in rational molecularly imprinted polymer design, especially with respect to recognition site heterogeneity.     

MOLECULARLY IMPRINTED POLYMERS FOR SOME REACTIVE DYES

Depending upon their structure, azo- and anthraquinonic dyes are the two major classes and together represent 90% of all organic colorants. Adsorption of dye molecules onto a sorbent can be an effective, low-cost method of color removal. Most of the techniques used for removal of dyes are of high production cost, and the regeneration also makes them uneconomical. There is much interest in the development of cheaper and effective newer materials for use as adsorbents. Molecular imprinting is a new kind of materials that can be alternative adsorbents. In this study, molecularly imprinted polymers of three textile dyes (Cibacron Orange P-4R, Cibacron Red P-4B, Cibacron Black PSG) were prepared. Methacrylic acid was used as a monomer for red and orange dyes and acrylamide was used for black dye. Methanol:acetonitrile was used as a porogen. The selective recognition ability of the molecularly imprinted polymers was studied by an equilibrium–adsorption batch method. The adsorption data are for Cibacron Black PSG 65% and nonimprinted polymer (NIP) 25%; Cibacron Red P-4B 72% and NIP 18%; and Cibacron Orange P-4R 45% and NIP 10%, respectively. Dye-imprinted polymers were used as a solid-phase extraction material for selective adsorption from wastewater of textile factory.     

Synthesis of CuPF6‐(S)‐BINAP loaded resin and its enantioselectivity toward phenylalanine enantiomers

A type of resin‐anchored CuPF₆‐(S )‐BINAP was synthesized and identified. The PS‐CuPF₆‐(S )‐BINAP resin was used to adsorb the phenylalanine enantiomers. The results showed that the adsorption capacity of PS‐CuPF₆‐(S )‐BINAP resin toward L‐phenylalanine was higher than that of resin toward D‐phenylalanine. PS‐CuPF₆‐(S )‐BINAP resin exhibited good enantioselectivity toward L‐phenylalanine and D‐phenylalanine. The influence of phenylalanine concentration, pH, adsorption time, and temperature on the enantioselectivity of the resin were investigated. The results showed that the enantioselectivity of the resin increased with increasing the phenylalanine concentration, pH, and adsorption time, while it decreased with an increase in temperature. The causes for these influences are discussed. The highest enantioselectivity (α = 2.81) was obtained when the condition of phenylalanine concentration was 0.05 mmol/mL, pH was 8, adsorption time was 12 h, and temperature 5°C. The desorption test for removing D/L‐phenylalanine on PS‐CuPF₆‐(S )‐BINAP resin was also investigated. The desorption ratios of D‐phenylalanine and L‐phenylalanine at pH of 1 were 95.7% and 94.3%, respectively. This result indicated that the PS‐CuPF₆‐(S )‐BINAP resin could be regenerated by shaking with an acidic solution. The reusability of the PS‐CuPF₆‐(S )‐BINAP resin was also assessed and the resin exhibited considerable reusability.     

Molecularly imprinted polymers for some reactive dyes

Depending upon their structure, azo- and anthraquinonic dyes are the two major classes and together represent 90% of all organic colorants. Adsorption of dye molecules onto a sorbent can be an effective, low-cost method of color removal. Most of the techniques used for removal of dyes are of high production cost, and the regeneration also makes them uneconomical. There is much interest in the development of cheaper and effective newer materials for use as adsorbents. Molecular imprinting is a new kind of materials that can be alternative adsorbents. In this study, molecularly imprinted polymers of three textile dyes (Cibacron Orange P-4R, Cibacron Red P-4B, Cibacron Black PSG) were prepared. Methacrylic acid was used as a monomer for red and orange dyes and acrylamide was used for black dye. Methanol:acetonitrile was used as a porogen. The selective recognition ability of the molecularly imprinted polymers was studied by an equilibrium-adsorption batch method. The adsorption data are for Cibacron Black PSG 65% and nonimprinted polymer (NIP) 25%; Cibacron Red P-4B 72% and NIP 18%; and Cibacron Orange P-4R 45% and NIP 10%, respectively. Dye-imprinted polymers were used as a solid-phase extraction material for selective adsorption from wastewater of textile factory.     

Synthesis of a trisulfated heparan sulfate disaccharide analog and its use as a template for preliminary molecular imprinting studies

A heparan sulfate disaccharide analog was synthesized by a multistep route. This synthesis was designed in such a way that one intermediate could be selectively deprotected to provide versatility during both synthesis and homologation of heparan sulfate related polysaccharides. Non-covalent imprinted polymers were prepared by using the synthesized disaccharide as a template and a primary amine functionalized acrylate as the key functional monomer suitable for specific sulfated sugar recognition. The binding of related sugars to the imprinted and non-imprinted polymers and the binding of template to the chemically modified polymers have been also investigated.     

Some new developments and challenges in non-covalent molecular imprinting technology

The technique of molecular imprinting allows the formation of specific recognition and catalytic sites in macromolecules via the use of templates. Molecularly imprinted polymers have been applied in an increasing number of applications where molecular binding events are of interest. These include the use of molecularly imprinted polymers as tailor-made separation materials, antibody and receptor binding site mimics in recognition and assay systems, enzyme mimics for catalytic applications and as recognition elements in biosensors. The stability and low cost of molecularly imprinted polymers make them advantageous for use in analysis as well as in industrial-scale production and application.     

A novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers for the enrichment and determination of polychlorinated biphenyls in fish samples

The novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers (rGO@m‐MIPs) were successfully synthesized as adsorbents for six kinds of polychlorinated biphenyls (PCBs) in fish samples. rGO@m‐MIPs was prepared by surface molecular imprinting technique. Besides, Fe₃O₄ nanoparticles (NPs) were employed as magnetic supporters, and rGO@Fe₃O₄ was in situ synthesis. Different from functional monomer and cross‐linker in traditional molecularly imprinted polymer, here, 3,4‐dichlorobenzidine was employed as dummy molecular and poly(ethylene‐co‐vinyl alcohol) was adopted as the imprinted polymers. After morphology and inner structure of the magnetic adsorbent were characterized, the adsorbent was employed for disperse solid phase extraction toward PCBs and exhibited great selectivity and high adsorption efficiency. This material was verified by determination of PCBs in fish samples combined with gas chromatography‐mass spectrometry (GC‐MS) method. According to the detection, the low detection limits (LODs) of PCBs were 0.0035–0.0070 µg l⁻¹ and spiked recoveries ranged between 79.90 and 94.23%. The prepared adsorbent can be renewable for at least 16 times and expected to be a new material for the enrichment and determination of PCBs from contaminated fish samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of the nature of MIP recognition: the development and characterisation of a MIP for Ibuprofen

This paper describes the rational design, generation and testing of a molecularly imprinted polymer specific for Ibuprofen. Ibuprofen is a member of the class of drugs termed non-steroidal anti-inflammatory drugs (NSAIDS). In the present study, Ibuprofen was used as a template molecule for the preparation of molecularly imprinted polymers. A MIP has been produced which is capable of recognising Ibuprofen in aqueous media. Furthermore, Ibuprofen can be selectively extracted from aqueous conditions by molecularly imprinted solid phase extraction (MISPE). Recoveries were typically high (>80%) and good selectivity for Ibuprofen over structurally related analogues was seen. Moreover, the nature of the recognition between MIP and template has been investigated by NMR and molecular modelling to analyse whether or not it is possible to predict how well a given MIP will perform under set conditions. In addition, the physical characteristics of the MIP have been investigated including the particle size distribution on exposure of the MIP to different solvents. This has been related to the ability of the MIP to rebind Ibuprofen under the same conditions. The data from the characterisation of the MIP has been used to further enhance the understanding of the nature of MIP recognition.     

Molecular imprinting of nitrophenol and hydroxybenzoic acid isomers: effect of molecular structure and acidity on imprinting

Three nitrophenol isomer-imprinted polymers were prepared under the same conditions using 4-vinylpyridine as a functional monomer. Different recognition capacities for template molecules were observed for the three polymers. Another imprinting system with stronger acidity than nitrophenol isomers, 2-hydroxybenzoic acid (salicylic acid) and 4-hydroxybenzoic acid, was imprinted using 4-vinylpyridine or acrylamide as functional monomer respectively. Both 4-hydroxybenzoic acid-imprinted polymers using the two monomers showed recognition ability for the template molecule. However, when acrylamide was chosen as functional monomer, the salicylic acid-imprinted polymer showed very weak recognition for the template molecule, whereas strong recognition ability of the resultant polymer for salicylic acid was observed with 4-vinylpyridine as functional monomer. It seems that the structure and acidity of template molecules is responsible for the difference in recognition, by influencing the formation and strength of interaction between template molecule and functional monomer during the imprinting process. An understanding of the mechanism of molecular imprinting and molecular recognition of MIPs will help to predict the selectivity of MIPs on the basis of template molecule properties.     

Design and evaluation of thin and flexible theophylline imprinted polymer membrane materials

The aim of this work was to produce a thin, flexible and diffusion able molecularly imprinted polymeric matrix with good template accessibility. Membranes were prepared using a non‐covalent molecular imprinting approach and their physical characteristics and binding capabilities investigated. Two materials were used, a poly(tri‐ethyleneglycol dimethyacrylate‐co‐methyl methacrylate‐co‐methacrylic acid) copolymer containing 14% cross‐linker and a monomer (g) to porogen (ml) ratio of 1:0.5 (A), and a blend of poly(TEGMA‐co‐MAA) and polyurethane (B). The polyurethane was added to improve membrane flexiblity and stability. The polymers were characterized using AFM, SEM and nitrogen adsorption, whilst binding was evaluated using batch‐rebinding studies. For all membranes the specific surface area was low (<10 m²/g). MIP (A) films were shown to bind specifically at low concentrations but specific binding was masked by non‐specific interactions at elevated concentrations. Selectivity studies confirmed specificity at low concentrations. K_D approximations confirmed a difference in the population of binding sites within NIP and MIP films. The data also indicated that at low concentrations the ligand‐occupied binding site population approached homogeneity. Scanning electron microscopy images of membrane (B) revealed a complex multi‐layered system, however these membranes did not demonstrate specificity for the template. The results described here demonstrate how the fundamental parameters of a non‐covalent molecularly imprinted system can be successfully modified in order to generate flexible and physically tolerant molecularly imprinted thin films. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecular recognition in synthetic polymers. Enantiomeric resolution of amide derivatives of amino acids on molecularly imprinted polymers

Molecular imprints were prepared using L-phenylalanine anilide as the print molecule and methacrylic acid as the functional monomer. Methacrylic acid interacts ionically with the primary amine of the print molecule and via hydrogen bonding with the amide function. In the HPLC mode such polymers were shown to exhibit efficient enantiomeric resolution of a racemic mixture of the original print molecule. Enantiomeric resolution was shown to be dependent on the ratio of methacrylic acid to print molecule in the pre-polymerization mixture and specific for the presence of both print molecule and functional monomer. Further analyses showed the importance of both the primary amino and amide functions in the correct stereochemistry for recognition and enantiomeric resolution of compounds on such polymers. Other amide derivatives of amino acids including p-nitroanilides, beta-naphthylamides and amides were recognized by such polymers, and enantiomeric resolution was obtained for amide derivatives of amino acid ranging from alanine to tryptophan on a single polymer. The implications of these findings with respect to the mechanism of recognition and the ability to predict enantiomeric resolution of molecules on molecularly imprinted polymers will be discussed.