Theoretical and experimental research on the self‐assembled system of molecularly imprinted polymers formed by salbutamol and methacrylic acid

The quantum chemical method was applied for screening functional monomers in the rational design of salbutamol‐imprinted polymers. Salbutamol was the template molecule, and methacrylic acid was the single functional monomer. The LC‐WPBE/6–31G(d,p) method was used to investigate the geometry optimization, active sites, natural bond orbital charges, binding energies of the imprinted molecule, and solvation energy. The mechanism of action between salbutamol and methacrylic acid was also discussed. The theoretical results show that salbutamol interacts with functional monomers by hydrogen bonds, and the salbutamol‐imprinted polymers with a ratio of 1:4 (salbutamol/methacrylic acid) in acetonitrile had the highest stability. The salbutamol‐imprinted polymers were prepared by precipitation polymerization. The experimental results indicated that the maximum adsorption capacity for salbutamol toward molecularly imprinted polymers was 7.33 mg/g, and the molecularly imprinted polymers had a higher selectivity for salbutamol than for norepinephrine and terbutaline sulfate. Herein, the studies can provide theoretical and experimental references for the salbutamol molecular imprinted system.     

Theoretical and experimental research on self‐assembly system of molecularly imprinted polymers formed via chloramphenicol and methacrylic acid

Chloramphenicol was chosen as the imprinting molecule and the methacrylic acid was chosen as the functional monomer to prepare molecularly imprinted polymers. Ethylene glycol dimethacrylate, pentaerythritol triacrylate, and trimethylolpropane trimethylacrylate were used as the cross‐linking agents, respectively. The interaction processes between chloramphenicol and methacrylic acid were simulated by using the ωB97XD/6‐31G (d,p) method. The self‐assembled configuration, bonding sites, binding number, binding energy, and interaction principle of stable complex formed by chloramphenicol and methacrylic acid with different molar ratios have been studied. The selectivity of the most stable complex formed from chloramphenicol and methacrylic acid was discussed with the thiamphenicol and florfenicol as the analogues of chloramphenicol. The results showed that chloramphenicol and methacrylic acid were interacted through the hydrogen bonds. When the molar ratio was 1:10 and pentaerythritol triacrylate as the cross‐linking agent, the ordered complex formed by chloramphenicol and methacrylic acid has the largest amount of hydrogen bonds and the lowest binding energy. Scatchard analysis showed that the maximum apparent adsorption capacity was 173.3 mg/g (0.536 mol/g), and the selection factor of florfenicol was the largest. This study provides a reliable theoretical and experimental basis for the design, preparation, and characterization of chloramphenicol molecularly imprinted polymers.     

三聚氰胺磁性分子印迹聚合物材料的制备及性能表征

利用溶剂热法通过控制反应时间和温度制得了分散性好和磁性强的Fe3O4,并利用溶胶凝胶法制备得到包覆SiO2的磁性微球(Fe3O4@SiO2)。以三聚氰胺为模板分子,甲基丙烯酸(MAA)为单体,采用本体聚合法制备了磁性分子印迹聚合物(MMIPs)。通过静态吸附实验表明,MMIPs对三聚氰胺的饱和吸附量高达10.22μg/mg,是磁性非印迹聚合物(MNIPs)的1.62倍。粒子扩散模型、Elovich模型和动态吸附实验表明所制得的MMIPs有较好的吸附性能。     

C-reactive protein thin-film molecularly imprinted polymers formed using a micro-contact approach

A method for micro-contact imprinting CRP has been developed. An analogue, O-(-4-nitrophenylphosphoryl)choline, of the templates natural ligand, phosphorylcholine, was used as the functional monomer. A series of non-imprinted polymers made without template, but with varying cross-linking agents, were made in order to produce a control polymer with minimal non-specific recognition.The affinity of the imprinted polymers for the competing proteins, lysozyme and albumin, was examined. Their respective relative affinities, with 1.04 μg/cm² of the template protein bound to the imprinted surface as reference, were CRP/albumin = 4.0 and CRP/lysozyme = 346. Measurement of the film thickness showed it to be approximately 10 μm.A competitive binding experiment showed the CRP imprinted material to retain good selectivity for its template when jointly incubated with human serum albumin and CRP. Using the same method we were able to form a micro-contact imprint of human serum albumin which demonstrated relatively good recognition for its own template 2.66 μg/cm² compared with 0.27 μg/cm² for CRP.     

Determination of domoic acid in shellfish extracted by molecularly imprinted polymers

A selective sample cleanup method using molecularly imprinted polymers was developed for the separation of domoic acid (a shellfish toxin) from shellfish samples. The molecularly imprinted polymers for domoic acid was prepared by emulsion polymerization using 1,3,5‐pentanetricarboxylic acid as the template molecule, 4‐vinyl pyridine as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, and Span80/Tween‐80 (1:1 v/v) as the composite emulsifiers. The molecularly imprinted polymer showed high affinity to domoic acid with a dissociation constant of 13.5 μg/mL and apparent maximum adsorption capacity of 1249 μg/g. They were used as a selective sorbent for the detection of domoic acid from seafood samples coupled with high‐performance liquid chromatography. The detection limit of 0.17 μg/g was lower than the maximum level permitted by several authorities. The mean recoveries of domoic acid from clam samples were 93.0–98.7%. It was demonstrated that the proposed method could be applied to the determination of domoic acid from shellfish samples.     

Carbohydrate recognition by porphyrin-based molecularly imprinted polymers

[structure: see text] Porphyrin-based molecularly imprinted polymers (MIPs) were prepared for carbohydrate recognition. A urea-appended porphyrin functional monomer was utilized to provide complementary functionality and quality binding sites throughout the polymer. Each porphyrin-based polymer demonstrates high affinity and differential selectivity for closely related carbohydrates that correlate to the structure of the template used in the imprinting process.     

三聚氰胺磁性表面分子印迹聚合物的制备及其在牛奶样品中的应用

以三聚氰胺（MEL）为模板分子、α-甲基丙烯酸（MAA）为功能单体、乙二醇二甲基丙烯酸酯（EGDMA）为交联剂、Fe₃O₄@SiO₂磁性材料为载体,制备得到三聚氰胺磁性表面分子印迹聚合物（MEL-MMIPs）。分别使用透射电镜（TEM）、热重分析（TGA）、傅立叶变换红外光谱（FT-IR）和振动样品磁强计（VSM）对制备的MMIPs进行表征。结果表明,印迹聚合物层成功地在Fe₃O₄@SiO₂磁性材料表面包覆,印迹粒子具有良好的磁学性能。将磁性分子印迹聚合物应用于牛奶中三聚氰胺的富集分离,采用高效液相色谱法（HPLC）检测,结果显示该磁性表面分子印迹聚合物对三聚氰胺有特异性吸附。以制备的MMIPs为吸附剂,建立了一种简单、快速和高选择性测定牛奶中三聚氰胺的方法。     

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 %.

Catalysis of benzisoxazole isomerization by molecularly imprinted polymers

A tailor-made catalytically active polymer catalyzing the benzisoxazole isomerization is described. Kinetic studies carried out in water/ethanol (3:1, v/v) at room temperature, showed a rate acceleration (k_MIP/k_control) of 7.2-fold compared to the control polymer. The imprinted polymer exhibits Michaelis-Menten kinetics with a K_m of 0.484 mM and a k_cat of 0.205 min⁻¹. Compared with the uncatalyzed reaction, a rate enhancement ((k_cat/K_m)/k_uncat) of 4 × 10⁴ fold was obtained. Substrate selectivity, accessible binding site analysis, dissociation constant determination, and inhibition study were also performed.     

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.     

Chromatographic characterization of molecularly imprinted polymers

Recent efforts in the investigation of chromatographic characterization of molecularly imprinted polymers (MIPs) have focused mainly on the nature of heterogeneous binding sites. More data on the thermodynamics than on the kinetic features of MIP columns have been published. The present article addresses the sources of peak broadening and tailing, which are the main drawbacks often associated with imprinted polymers in chromatography for practical applications. With use of the theory of nonlinear chromatography, the peak properties of a MIP column, including the retention and peak broadening and tailing, can be well interpreted. Efforts to improve chromatographic efficiency using MIPs prepared by approaches different from the conventional method, including covalent imprinting and the format of uniformly sized spherical microbeads, are reviewed and discussed. This review leads to the conclusion that nonlinear chromatography theory is useful for characterizing chromatographic features of MIP columns, since a MIP is essentially an affinity-based chromatographic stationary phase. We expect more theoretical and experimental studies on the kinetic aspects of MIP columns, especially the factors influencing the apparent rate constant, as well as the analysis of the influences of mobile-phase composition on the chromatographic performance. In addition to revealing the affinity interaction by molecular recognition, slow nonspecific interactions which may be inherited from the imperfect imprinting and may be involved in the rebinding of the template to MIPs also need to be characterized. Figure The peak broadening and tailing associated often with molecularly imprinted polymers (MIPs) in column chromatography for practical applications can be well characterized by the theory of nonlinear chromatography.     

Theoretical design,preparation, and evaluation of Ginkgolide B molecularly imprinted polymers

Ginkgolide B is in great demand worldwide on account of its extensive and excellent pharmacological effects, however, it is difficult to separate and purify ginkgolide B. In this study, ginkgolide B molecularly imprinted polymers were prepared by combining software simulation and molecular imprinting technique, and its characterization and adsorption performed evaluation were performed to understand the adsorption behavior of the polymers. The adsorption equilibrium concentration of molecularly imprinted polymers was 0.70 mg/mL, and the adsorption equilibrium time was 4 h. Meanwhile, the adsorption isotherm of the polymers for ginkgolide B fitted well with the Langmuir model, and the adsorption kinetics was in line with the pseudo‐second‐order kinetics. In contrast, the adsorption capacity of molecularly imprinted polymers on ginkgolide B was higher than that of non‐molecular imprinted polymers, with better selectivity and better adsorption after repeated use for six times. The application experiments showed that molecular imprinted polymers have a good adsorption effect in low purity samples. Therefore, the polymers reported herein can be expected to apply in the adsorption and separation of ginkgolide B samples.     

Enantiomeric resolution of amino acid derivatives on molecularly imprinted polymers as monitored by potentiometric measurements

Potentiometric measurements have been applied to the detection of enantiomeric separations on molecularly imprinted polymers. A flow-through column electrode, based on the use of polymers imprinted against L-phenylalanine anilide, is described. The electrode consisted of a glass column in which the polymer was packed and where the end frits constituted the electrodes. The flow stream potential across the column can be continuously recorded as solvent is pumped through the system. The column resolved the enantiomers of phenylalanine anilide as detected by both UV absorption and potentiometric measurements and the recorded signals could be correlated with the concentration of phenylalanine anilide. The calibration graphs obtained for the UV absorption of phenylalanine anilide were linear over the concentration range investigated, whereas the potentiometric signal was shown to be exponentially linear with concentration. The application of molecular imprints to the preparation of supports suitable for chromatographic separations of enantiomers and for the preparation of specific electrodes is discussed.     

Comparison of multi-recognition molecularly imprinted polymers for recognition of melamine,cyromazine, triamterene,and trimethoprim

Three fragmental templates, including 2,4-diamino-6-methyl-1,3,5-triazine (DMT), cyromazine (CYR), and trimethoprim (TME), were used to prepare the fragment molecularly imprinted polymers (FMIPs), respectively, in polar ternary porogen which was composed of ionic liquid ([BMIM]BF₄), methanol, and water. The morphology, specific surface areas, and selectivity of the obtained FMIPs for fragmental analogues were systematically characterized. The experimental results showed that the FMIPs possessed the best specific recognition ability to the relative template and the greatest imprinting factor (IF) was 5.25, 6.69, and 7.11 of DMT on DMT-MIPs, CYR on CYR-MIPs, and TME on TME-MIPs, respectively. In addition, DMT-MIPs also showed excellent recognition capability for fragmental analogues including CYR, melamine (MEL), triamterene (TAT), and TME, and the IFs were 2.08, 3.89, 2.18, and 2.60, respectively. The effects of pH and temperature on the retention of the fragmental and structural analogues were studied in detail. Van’t Hoff analysis indicated that the retention and selectivity on FMIPs were an entropy-driven process, i.e., steric interaction. The resulting DMT-MIPs were used as a solid-phase extraction material to enrich CYR, MEL, TAT, and TME in different bio-matrix samples for high-performance liquid chromatography analysis. The developed method had acceptable recoveries (86.8–98.6 %, n?=?3) and precision (2.7–4.6 %) at three spiked levels (0.05–0.5 μg g^?1).     

水杨酸分子印迹电化学传感器的制备及其性能研究

以水杨酸作为模板分子,通过原位聚合法,在玻碳电极表面合成了水杨酸分子印迹聚合物膜,并用方波伏安法对该印迹电极进行了分析研究.当吸附时间为7 min时,印迹电极对水杨酸浓度响应的线性范围为1.0×10-5~2.6×10-5mol/L,检出限(S/N=3)为2.0×10-6mol/L,同一支印迹电极对水杨酸响应值的RSD为...     

Recognition characteristics of dibenzofuran by molecularly imprinted polymers made of common polymers

Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of commercially available polymers: polyvinyl chloride (PVC), polysulfone, polystyrene, and polyacrylonitrile. Preparation of MIPs was carried out by phase inversion of the polymer. Respective polymer solutions were coagulated with DBF template in water (non-solvent). In addition, reference polymers without the template were prepared in same manner as unimprinted polymers. After the DBF template was extracted from the solidified polymers by washing with methanol (MeOH), recognition experiments of DBF by the imprinted polymers were carried out for DBF in MeOH solutions. Equilibrium constants for DBF were calculated from saturation binding kinetics. Equilibrium experiment results reveal that recognition was effective for DBF binding to the DBF-imprinted polymer, especially for the imprinted PVC.     

Chiral recognition by molecularly imprinted polymers in aqueous media

Summary Molecularly imprinted polymers were prepared using 2-vinylpyridine and/or methacrylic acid as functional monomers in a self-assembly imprinting protocol. The resulting polymers were analyzed in aqueous media, and the effects from the pH of the mobile phase and the degree of added organic solvent were investigated. The results are indicative of the importance of ionic bonds in conjunction with hydrophobic interactions in the formation of the complexes between the analyte and the polymers.     

Preparation of melamine molecularly imprinted polymer by computer‐aided design

Melamine was chosen as template, methacrylic acid was chosen as functional monomer, and divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane trimethylacrylate were chosen as cross‐linking agents, respectively. The WB97XD/6‐31G(d, p) method was used to calculate the geometry optimization of the different imprinting ratios, the action sites, the bonding situation, and the optimization of the cross‐linking agents. The nature of the imprinting effect was also studied by the atoms in molecules theory. The theoretical results showed that melamine interacts with methacrylic acid by hydrogen bonding, and the melamine molecularly imprinted polymers with a molar ratio of 1:6 have the most hydrogen bonds and the most stable structure. Divinylbenzene is the best cross‐linking agent for the melamine molecularly imprinted polymers. The melamine molecularly imprinted polymers were synthesized by precipitation polymerization. The results showed that the maximum adsorption capacity for molecularly imprinted polymers towards melamine is 19.84 mg/g, and the adsorption quantity of the polymers to melamine is obviously higher than that of cyromazine, cyanuric acid, and trithiocyanuric in milk. This study could provide theoretical and experimental references for the screening of the imprinting ratio and the cross‐linking agent for the given template and monomer system.     

New configurations and applications of molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are applicable in a variety of different configurations. For example, bulk polymers imprinted with beta-lactam antibiotics are presented to be used as stationary phases for the chromatographic separation of beta-lactam antibiotics with both aqueous and organic mobile phases. However, in some analytical applications, monosized spherical beads are preferred over the currently used ground bulk polymers. A precipitation polymerization technique allows preparation of monosized spherical imprinted beads with diameters down to 200 nm having excellent recognition properties for different target molecules. Nevertheless, with current imprinting protocols a substantial amount of template has to be used to prepare the polymer. This can be problematic if the template is poorly soluble, expensive or difficult to obtain. It is shown that for analytical applications, the functional monomer:template ratio can be drastically increased without jeopardizing the polymer's recognition properties. Furthermore, a substantial reduction of the degree of crosslinking is demonstrated, resulting in much more flexible polymers that are useful for example the preparation of thin imprinted films and membranes for sensors. Apart from analysis, MIPs also are applicable in chemical or enzymatic synthesis. For example, MIPs using the product of an enzyme reaction as template are utilized for assisting the synthetic reaction by continuously removing the product from the bulk solution by complexation. This results in an equilibrium shift towards product formation.     

Dopamine sensor based on molecularly imprinted electrosynthesized polymers

Molecularly imprinted polymers (MIPs) have been applied as molecular recognition elements to chemical sensors. In this paper, we combined the use of MIPs and electropolymerization to produce a sensor which was capable of detecting dopamine (DA). The MIP electrode was obtained by electrocopolymerization of o-phenylenediamine and resorcinol in the presence of the template molecular DA. The MIP electrode exhibited a much higher current response compared with the non-imprinted electrode. The response of the imprinted sensor to DA was linearly proportional to its concentration over the range 5.0 × 10⁻⁷-4.0 × 10⁻⁵ M. The detection limit of DA is 0.13 μM (S/N = 3). Moreover, the proposed method could discriminate between DA and its analogs, such as ascorbic acid and uric acid. This method was successfully applied to the determination of DA in dopamine hydrochloride injection and healthy human blood serum. These results revealed that such a sensor fulfilled the selectivity, sensitivity, sped, and simplicity requirements for DA detection and provided possibilities of clinical application in physiological fields.