Detection of functional states of molecularly imprinted thin films with multi-cycling nanoindentation

Molecular imprinting is a chemical technique for the production of molecule-specific cavities. Spin casting with amino acids, aromatic molecules, carbohydrates or pesticides used as template molecules produces thin, selectively imprinted films of nylon-6 and other polymers. The film recognition activity is clearly coordinated with the appearance of nanometer-sized pores. The mechanical properties of the imprinted network reflect the various functional states of molecularly imprinted polymer films. Three specific functional states of the MIP were observed. Pores filled by template molecules may be distinguished from empty pores due to the variation in the elasticity modulus, the viscoelasticity and the hardness. The presence of the template molecule makes the polymer matrix stiffer due to strong hydrogen bonds (or other interactions) with the polymer chains. Films with empty pores have a higher viscoelasticity than those with filled pores. Changes in the polymer network are directly related to the nanomechanical properties and systematically studied in this work.     

Diosgenin-selective molecularly imprinted pearls prepared by wet phase inversion

Functional poly(acrylonitrile-co-acrylic acid) imprinted pearls, selective for diosgenin – a steroidal saponin with the ability to reduce cholesterol from blood – were prepared by wet phase inversion. Three copolymers with the monomer ratios AN:AA90:10, 80:20, and 70:30 where used to prepare the corresponding MIPs (molecularly imprinted polymers) and NIPs (non-imprinted polymers).The rheology studies showed that an 8 w% solution of copolymer in dimethylformamide lead fastest to robust, spherical pearls. Affinity centres were generated via non-covalent bonding between diosgenin’s hydroxyl groups and carboxyl moieties of the copolymer matrix. The presence and the quality of the selective binding sites in MIPs were highlighted by optic and electronic microscopy, infrared spectroscopy, thermal analyses, and batch rebinding tests. The imprinting factor (IF) values, ranging from 1.9 to 4.35, decrease with the increasing of the initial concentration of feed solution. When comparing the MIPs concerning the AN:AA ratio, the IF decreases in the order AN:AA80:20 > AN:AA70:30 > AN:AA90:10, suggesting that the 80:20 ratio is the optimum compromise between selectivity (given by AA) and resistance (given by AN). For the best imprinted MIP, 80:20, affinity tests were performed with three competitors, obtaining the average affinity 54%, compared with 31%, 11%, and 4% for the competitors.     

Preparation and characterization of monodisperse molecularly imprinted polymer microspheres by precipitation polymerization for kaempferol

A new kind of molecularly imprinted polymer (MIP) microspheres for the selective extraction of kaempferol was prepared by precipitation polymerization using 4-vinylpridine (4-VP) and ethylene glycol dimethacrylate (EDMA) as functional monomer and cross-linker respectively. The synthesis conditions, such as ratios of 4-VP/EDMA and polymerization time were discussed in detail. Results showed that the 2% was the optimal concentration of co-monomers to obtain monodisperse MIP microspheres, the best ratio of 4-VP/EDMA was 1:2, and 24 h was considered as the proper polymerization time. Compared with the MIP agglomeration or coagulum particles, monodisperse MIP microspheres showed the better adsorption capacity: the saturated adsorption capacity of monodisperse MIP microspheres was 7.47 mg g^?1, the adsorption equilibrium could be obtained in 30 min. Finally, the adsorption performances of the optimal MIP microspheres were evaluated by kinetic adsorption, adsorption isotherm, and selective adsorption experiments, which indicated that the adsorption mechanism were chemical single layer adsorption and the separation factor was up to 3.91 by comparing with the structure similar compound (quercetin). The MIP microspheres exhibit prospects in the kaempferol efficient and selective separation.     

格列美脲分子印迹聚合物应用于固相萃取的研究

以降血糖药物格列美脲为模板分子,ɑ-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,采用本体聚合法制备了格列美脲分子印迹聚合物(MIP),用于血浆样品前处理,建立了对加标兔血浆中格列美脲含量的固相萃取检测方法,通过高效液相色谱法测定,分子印迹固相萃取柱的回收率可达80%以上,有效地减少了基体中蛋白质等杂质对目标物检测的干扰,适用于生物样品中模板分子的富集和纯化。     

The influence of polymer morphology on the performance of molecularly imprinted polymers

This is the first in-depth study examining the effect of morphology on the performance of 2-aminopyridine (2-apy) imprinted polymers. A series of polymers were prepared by varying the amount of crosslinking monomer (EGDMA) whilst the other polymer components remained constant. Physical characterisation was carried out using conventional techniques, such as nitrogen sorption porosimetry and solvent swelling studies. The use of a novel thermal desorption GC-MS technique suggested higher levels of polymer degradation with prolonged exposure to elevated temperatures for those polymers formed with lower amounts of EGDMA. The thermal desorption GC-MS profiles obtained correlated with the physical characteristics of the polymers, where higher levels of polymer bleed was found to occur with larger average pore diameters. Polymer physical characteristics were also found to correlate with the binding parameters (number of binding sites and polymer-template association energy) obtained from the Langmuir-Freundlich Isotherm (L-FI) and affinity distribution spectra (AD). The flexibility of the polymers formed from lower amounts of EGDMA combined the swelling effect of the solvents on the polymers resulted in an increase in affinity, which was both specific and non-specific in nature.     

Preparation and characterization of molecularly imprinted silica particles for selective adsorption of naphthalene

A new kind of molecularly imprinted adsorbent for naphthalene was prepared by a covalent/noncovalent hybrid strategy. The monomer-template compound was prepared by the reaction of 3-(triethoxysilyl)propyl isocyanate with β-naphthol to form a thermally cleavable urethane bond. The silica gel was prepared by means of the gelation of monomer-template compound with tetraethoxysilane in ethanol using sol–gel technology. The removal of the template by the cleavage of urethane bond at elevated temperature resulted in the generation of recognition sites which could rebind naphthalene through noncovalent interaction. Binding experiments demonstrated that the imprinted silica particles showed a very fast uptake profile for naphthalene and displayed highly selective recognizing ability for naphthalene over benzene and other PAHs such as anthracene, phenanthrene, pyrene, fluoranthene and triphenylene.     

The effect of polymerisation methods on the adsorption capacity of HEMA based molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are generally synthesised either by thermal initiation or by photo polymerisation methods. Recently we used a gamma irradiation method for the preparation of MIPs. In this communication we compare three different methods for the synthesis of 2-hydroxy ethyl methacrylate (HEMA) based MIP imprinted for hydrocortisone in terms of its capacity to adsorb the print molecule. Our results show that MIP prepared by the gamma irradiation method has a better adsorption capacity than the thermally initiated polymer. It is interesting to note that its adsorption capacity is comparable or marginally better than the photo polymerised MIP.     

分子印迹固相萃取法提取花生壳中木犀草素

采用分子印迹技术,以木犀草素为模板分子、丙烯酰胺为功能单体、EGDMA为交联剂,合成了木犀草素印迹聚合物。将该印迹聚合物用于固相萃取,分离提取花生壳中的木犀草素。结果表明,该印迹聚合物对木犀草素具有较高的吸附性能和选择性,用印迹柱萃取得到的木犀草素纯度高出硅胶柱分离近20个百分点,达到96.2%。且MIPs-SPE柱与普通的硅胶柱相比,经过洗脱再生后可以反复使用多次。     

Promethazine determination in plasma samples by using carbon paste electrode modified with molecularly imprinted polymer (MIP): Coupling of extraction, preconcentration and electrochemical determination

A promethazine (PMZ) molecularly imprinted polymer (MIP) and a non-imprinted polymer (NIP) were synthesized by two different formulations of methacrylic acid-ethylene glycol dimethacrylate (MAA-EGDMA) and vinyl benzene-divinyl benzene (VB-DVB). Then, the MIPs were used to modify the carbon paste electrode (CP). The response difference between MIP-CP and NIP-CP electrodes, containing VB-DVB polymer, was higher than that for MIP-CP and NIP-CP modified with polymer of MAA-EGDMA, indicating the lower nonselective surface adsorption property of the VB-DVB based MIP. The MIP, incorporated in the carbon paste electrode, functioned as selectively recognition element and pre-concentrator agent for PMZ determination. The prepared electrode was used for PMZ measurement by the three steps procedure including analyte extraction in the electrode, electrode washing and electrochemical measurement of PMZ. It was shown that the electrode washing, after PMZ extraction, led to enhanced selectivity. Square wave voltammetry (SWV) for PMZ determination by proposed electrode was proved to be better than that of differential pulse voltammetry. Some parameters, effective on the electrode response, were optimized and then a calibration curve was plotted. Two dynamic linear range of 7 × 10⁻⁹ to 4 × 10⁻⁷ and 4 × 10⁻⁷ to 7 × 10⁻⁶ mol L⁻¹ were obtained. The detection limit of the method was calculated equal to 3.2 × 10⁻⁹ mol L⁻¹. This method was used successful for PMZ determination in blood serum sample.     

Preparation of the molecularly imprinted polymers-based capacitive sensor specific for tegafur and its characterization by electrochemical impedance and piezoelectric quartz crystal microbalance

Molecularly imprinted polymers (MIPs)-based capacitive sensor specific for tegafur was constructed by electropolymerization of m-aminophenol onto the surface of gold electrode and the Au-coated quartz crystal electrodes. Electrochemical impedance (EI) and quartz crystal microbalance (QCM) were employed to characterize the modified gold electrodes and the modified Au-coated quartz crystals, respectively. Unlike the capacitive sensors reported in the previous literatures, the present sensors were not treated with alkanethiol after electropolymerization and show even more satisfactory performance. QCM measurements also confirmed the imprinting effect of the polymer layers.     

分子印迹聚合物微球对亚甲基蓝的去除特性研究

以亚甲基蓝为模板分子,丙烯酰胺为功能单体,乙二醇二甲基丙烯酸酯（EGDMA）为交联剂,偶氮二异丁腈（AIBN）为引发剂．采用沉淀聚合法制备了亚甲基蓝分子印迹聚合物微球（MIP）。用扫描电镜表征了MIP的形貌,结果显示制备的MIP的粒径为1～3μm,粒径较为均匀。考察了MIP对亚甲基蓝的吸附性能,结果表明其吸附动力学过程可以用假二级吸附速率方程来描述,MIP对亚甲基蓝的最大吸附量为27．1mg／g,吸附效果较好,可以用于染料废水中亚甲基蓝的分离富集。     

Optimisation of the synthesis of vancomycin-selective molecularly imprinted polymer nanoparticles using automatic photoreactor

A novel optimized protocol for solid-state synthesis of molecularly imprinted polymer nanoparticles (nanoMIPs) with specificity for antibiotic vancomycin is described. The experimental objective was optimization of the synthesis parameters (factors) affecting the yield of obtained nanoparticles which have been synthesized using the first prototype of an automated solid-phase synthesizer. Applications of experimental design (or design of experiments) in optimization of nanoMIP yield were carried out using MODDE 9.0 software. The factors chosen in the model were the amount of functional monomers in the polymerization mixture, irradiation time, temperature during polymerization, and elution temperature. In general, it could be concluded that the irradiation time is the most important and the temperature was the least important factor which influences the yield of nanoparticles. Overall, the response surface methodology proved to be an effective tool in reducing time required for optimization of complex experimental conditions.     

Synthesis and application of a molecularly imprinted polymer as a filter to reduce polycyclic aromatic hydrocarbon levels in mainstream cigarette smoke

The design and fabrication of novel filter is a promising approach to realize the reduction of harmful substance in mainstream cigarette smoke. In our work, a kind of pyrene (PYR) imprinted polymer as a part of improved filter has been successfully synthesized for the determination of polycyclic aromatic hydrocarbons (PAHs) in mainstream cigarette smoke. The molecularly imprinted polymers (MIPs) showed an good affinity towards PYR with binding capacity (Q_max) of 18.33 mg/g. Accordingly, the MIPs were used as a solid phase extraction (SPE) sorbent for the extraction and enrichment of PAHs in mixed samples to evaluate the selectivity about the MIPs. When the cellulose acetate (CA)-filter was replaced by a MIPs-filter, the amount of PAHs in the mainstream smoke was reduced by 63.6%. The application will provide technical support for the design of functional filters to reduce the harms brought by cigarette suction.     

Extraction and determination of malachite green from aquatic products based on molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) were synthesized using malachite green (MG) as template, and methacrylic acid/sodium methacrylate as composite monomers. The equilibrium dissociation constant and apparent maximum adsorption capacity of the MIPs reach 12.2 mg·L^?1 and 3.2 mg·g^?1, respectively. The MIPs demonstrate excellent recognition ability due to high-affinity sites constructed by the electrostatic interaction and hydrogen bonds between template and composite monomers. The MIPs were successfully employed for the detection of MG residue in aquatic products coupled with high-performance liquid chromatography (HPLC) with a detection limit of 0.57 μg·kg^?1.     

Magnetic temperature-sensitive molecularly imprinted materials for separation and enrichment of single component of formononetin in medicinal plants

The magnetic and temperature double response molecularly imprinted polymers for formononetin-specific adsorption (MTMIPs) were successfully prepared by using Fe₃O₄ as supporting matrix, formononetin as template, N-isopropyl acrylamide as the thermo-sensitive type functional monomer and methacrylic acid as auxiliary functional monomer. SEM, TEM, FT-IR, TGA and magnetic analysis were used to characterize the structure of MTMIPs, and then their adsorption properties and reproducibility were investigated. The results showed that MTMIPs was a core-shell structure with good thermal stability, good adsorption performance (16.43 mg/g) and fast adsorption performance. The adsorption kinetics of formononetin was consistent with the quasi-second-order kinetics model, and the adsorption process was consistent with the Langmuir monolayer adsorption with good reproducibility. HPLC test results show that MTMIPs can be used to separate and enrich formononetin from complex samples.     

磁性温敏分子印迹材料用于药用植物中富集单一成分——芒柄花黄素的分离与富集

以四氧化三铁(Fe3O4)纳米粒子为支撑材料,模板选用芒柄花黄素,温敏功能单体和辅助功能单体分别选用N-异丙基丙烯酰胺(NIPAM)和甲基丙烯酸(MAA),制备出磁性和温度双响应型分子印迹材料(MTMIPs),并结合高效液相色谱法(HPLC)将其用于红车轴草中芒柄花黄素的定向萃取研究。利用扫描电镜(SEM)、透射电镜(TEM)、红外光谱(FT-IR)、热重分析(TGA)、磁性分析(VSM)等手段对MTMIPs进行表征,随后对其温敏及吸附性能进行考察。结果表明,MTMIPs为核壳型结构,热稳定性好,具有良好的吸附性能(16.43 mg/g)和温敏特性,对芒柄花黄素的吸附动力学符合准二级动力学模型,吸附过程符合Langmuir单分子层吸附。HPLC检测结果显示MTMIPs可用于从复杂样品中分离富集芒柄花黄素。     

Selective extraction and determination of sumatriptan succinate in human urine by synthesized thermosensitive molecularly imprinted poly(3-allyloxy-1, 2-propanediol/N-vinylcaprolactam)

ABSTRACT

In this research, a drug-imprinted polymer upon polymerization was done with 3-allyloxy-1, 2-propanediol as a functional monomer, N-vinyl caprolactam as a thermosensitive monomer, N, N′-methylenebisacrylamide, as a cross-linker agent, sumatriptan succinate as a template and azobis isobutyronitrile as an initiator. The engineered drug-imprinted polymer was evaluated by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and scanning electron microscopy. The drug-imprinted polymer sorbent operated selective for sumatriptan succinate. This study examines the determination of sumatriptan succinate in human urine and plasma samples by high-performance liquid chromatography with great results.     

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