Molecularly imprinted polymer sensor arrays

An eight channel molecularly imprinted polymer sensor array was prepared that was able to differentiate six different aryl amine analytes, including diastereomers with 94% accuracy.     

Molecularly imprinted conducting polymer based electrochemical sensor for detection of atrazine

An original electrochemical sensor based on molecularly imprinted conducting polymer (MICP) is developed, which enables the recognition of a small pesticide target molecule, atrazine. The conjugated MICP, poly(3,4-ethylenedioxythiophene-co-thiophene-acetic acid), has been electrochemically synthesized onto a platinum electrode following two steps: (i) polymerization of comonomers in the presence of atrazine, already associated to the acetic acid substituent through hydrogen bonding, and (ii) removal of atrazine from the resulting polymer, which leaves the acetic acid substituents open for association with atrazine. The obtained sensing MICP is highly specific towards newly added atrazine and the recognition can be quantitatively analyzed by the variation of the cyclic voltammogram of MICP. The developed sensor shows remarkable properties: selectivity towards triazinic family, large range of detection (10⁻⁹ mol L⁻¹ to 1.5 × 10⁻² mol L⁻¹ in atrazine) and low detection threshold (10⁻⁷ mol L⁻¹).     

Molecularly imprinted polymer as a solid phase extractor in flow analysis

Molecularly imprinted polymers (MIPs) are novel alternative materials for solid phase extraction. Applications in flow analysis are recent and enhanced in-line separation/concentration procedures have been proposed. Use of flow systems is very important in the context. The aim of this review is then to highlight the implementation of MIP as solid phase extractor in flow analysis, emphasizing potentialities, limitations and applications.     

Molecularly imprinted polymer coated magnetite nanoparticles as an efficient mefenamic acid resonance light scattering nanosensor

In this work, a mefenamic acid (MFA) nanosensor was synthesized by the aid of molecularly imprinted polymer (MIP) technique. MIP layer was coated on magnetite nanoparticles as magnetic nano-carriers. Synthesized nanoparticles were characterized using various measurements techniques. Light scattering properties of the synthesized nanoparticles in the presence or absence of MFA have been selected as the detection signal. In this regard, resonance light scattering has been used as the detection method. Various factors that can potentially affect light scattering efficiency (i.e., pH, ultrasonication time and nanoparticle dosage) were optimized using “one-at-a-time” method. A linear dynamic range was established from 100.0 to 2000.0 ng L⁻¹ of MFA and the limit of detection was found to be 50.0 ng L⁻¹ using the proposed method.     

Molecularly imprinted polymers for the selective solid-phase extraction of chloramphenicol

A variety of bulk polymers for the selective separation of chloramphenicol were synthesised from 2-vinylpyridine, diethylaminoethyl methacrylate or methacrylic acid monomers. Chromatographic evaluation indicated that chloramphenicol was retained under nonpolar elution conditions (k = 58.65) through selective hydrogen bonding and ionic interactions. The retention of chloramphenicol under aqueous elution conditions (k > 100) results from nonselective hydrophobic interactions. Under nonpolar elution conditions, the functional monomer employed imparted a significant influence on the recognition properties of the corresponding polymer. After solid-phase extraction using a molecularly imprinted polymer as sorbent and either an organic or aqueous washing solvent, nearly 100% recovery from the chloramphenicol standard solution was achieved, and nearly 90% recovery could be attained from spiked honey samples. The molecularly imprinted polymer was well suited to suppress matrix effects, and provided optimal preconcentration of the target molecule (chloramphenicol) prior to chromatographic analysis.     

An optical reflected device using a molecularly imprinted polymer film sensor

A novel and highly selective optical sensor with molecularly imprinted polymer (MIP) film was fabricated and investigated. The optical sensor head employing a medium finesse molecularly imprinted polymer film has been fabricated and characterised. A blank polymer and formaldehyde imprinted polymer were using methacrylic acid as the functional monomer and the ethylene glycol dimethacrylate as a crosslinker. The transduction mechanism is discussed based on the changes of optical intensity of molecularly imprinted polymer film acting as an optical reflected sensor. Template molecules, which diffused into MIP, could cause film density, and refractive index change, and then induce measurable optical reflective intensity shifts. Based on the reflective intensity shifts, an optical reflection detection of formaldehyde was achieved by illuminating MIP with a laser beam. For the same MIP, the reflective intensity shift was proportional to the amount of template molecule. This optical sensor, based on an artificial recognition system, demonstrates long-time stability and resistance to harsh chemical environments. As the research moves forward gradually, we establish the possibilities of quantitative analysis primly, setting the groundwork to the synthesis of the molecular imprinted optical fiber sensor. The techniques show good reproducibility and sensitivity and will be of significant interest to the MIPcommunity.     

A molecularly imprinted photonic polymer sensor with high selectivity for tetracyclines analysis in food

A molecularly imprinted photonic polymer (MIPP) sensor for respective detection of tetracycline, oxytetracycline and chlortetracycline is developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. Colloidal crystal templates are prepared from monodisperse polystyrene colloids. The molecularly imprinted polymer, which is embodied in the colloidal crystal templates, is synthesized with acrylic acid and acrylamide as monomers, N,N'-methylene bisacrylamide as a cross-linker and tetracyclines (TCs) as imprinting template molecules. After removal of the colloidal crystal template and the molecularly imprinted template, the resulted MIPP consists of a three-dimensional, highly ordered and interconnected macroporous array with a thin hydrogel wall, where nanocavities complementary to analytes in shape and binding sites are distributed. The response of MIPP to TCs stimulants in aqueous solution is detected through a readable Bragg diffraction red-shift, which is due to the lattice change of MIPP structures responding to their rebinding to the target TCs molecules. A linear relationship was found between the Δλ and the concentration of TCs in the range from 0.04 μM to 0.24 μM. With this sensory system, direct and selective detection of TCs has been achieved without using label techniques and expensive instruments. The developed method has been applied successfully to detect tetracycline in milk and honey samples.     

Molecularly imprinted polymers as biomimetic catalysts

The quest for synthetic biomimetic catalysts able to complement the activity of enzymes has attracted substantial research efforts, and the molecular imprinting approach is one of the attractive techniques that are currently being investigated. In the last 3 years, there has been considerable interest in studying in greater detail the parameters that control and influence the catalytic activity of imprinted polymers and applying molecular imprinting to a wider range of polymeric matrices. This article reports on some of the interesting examples available in the literature regarding the use of metal-containing polymers, microgels and nanogels and thermoresponsive polymers.     

Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids

Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of hydroxyzine in tablets and biological fluids. The molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization, using hydroxyzine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited a Nernstian response (29.4 ± 1.0 mV decade⁻¹) in a wide concentration range of 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a lower detection limit of 7.0 × 10⁻⁷ M. The electrode demonstrated a response time of ∼15 s, a high performance and a satisfactory long-term stability (more than 5 months). The method has the requisite accuracy, sensitivity and precision to assay hydroxyzine in tablets and biological fluids.     

利用辅助识别聚合物链制备牛血清白蛋白分子印迹聚合物

论文提出了一种新的蛋白质分子印迹方法, 即以聚乙烯醇接枝聚合物作为辅助识别聚合物链(ARPCs), 以丙烯酰胺为单体, 在丙烯酸酯树脂载体表面进行聚合, 制备牛血清白蛋白分子印迹树脂. 实验使用2.00 mol•L⁻¹氯化钾(KC1)溶液除去模板蛋白质, 使用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测吸附蛋白质, 并设计使用0.150, 0.500和2.00 mol•L⁻¹KC1溶液分别对吸附蛋白质进行梯度洗提. 电泳实验结果表明, 2.00 mol•L⁻¹KC1溶液洗脱的蛋白质是大孔树脂的吸附效应; 0.500 mol•L⁻¹KC1溶液洗脱掉的是印迹蛋白质. 引入ARPCs制得的分子印迹树脂, 用于混合蛋白质体系吸附时, 对模板蛋白质的吸附量为80~100μg•g⁻¹, 其特异性吸附能力较未引入ARPCs之前有明显提高.     

Molecularly imprinted polymer as SPE sorbent for selective extraction of melamine in dairy products

In this paper, a highly selective sample cleanup procedure combining molecular imprinting and solid-phase extraction (MI-SPE) was developed for the isolation of melamine in dairy products. The molecularly imprinted polymer (MIP) was prepared using melamine as the template molecule, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linking monomer. The melamine imprinted polymer was used as selective sorbent for the solid-phase extraction of melamine from dairy products. An off-line MI-SPE method followed by high-performance liquid chromatography with diode-array detection for the detection of melamine was also established. The mean recoveries of melamine from ultra-heat treatment (UHT) milk and milk powders were 92.9-98.0% and 91.6-102.8%, respectively. Good linearity was obtained from 0.5 μM to 10 μM (r > 0.999) with a quantitation limit of 0.5 μmol/L (0.06 ppm) which was sufficient to analyse melamine at the maximum level permitted by U.S. Food and Drug Administration (1 ppm) in dairy products. It was demonstrated that the proposed MI-SPE-HPLC method could be applied to direct determination of melamine in dairy products.     

Molecularly imprinted polymer using beta-cyclodextrin as functional monomer for the efficient recognition of bilirubin

Bilirubin (BR) imprinted polymer was successfully prepared using supramolecular host compound β-cyclodextrin (β-CD) as functional monomer. The adsorption equilibrium was attained in about 4 h, which indicated that the adsorption kinetics was comparatively fast. The results of adsorption and selectivity experiments indicated that BR-imprinted β-CD polymer was able to bind BR specifically and reversibly. The specific recognition of BR-imprinted β-CD polymer for BR may be due to the cooperative effects of inclusion interaction and hydrogen bonding. This BR-imprinted β-CD polymer was further applied to eliminate BR in human serum sample. It was verified that the binding specificity of the BR-imprinted polymer for BR was essentially sufficient in the presence of other compounds coexisting in serum sample. Therefore, as a reusable material possessing high affinity and selectivity, BR-imprinted β-CD polymer has a potential application perspective as a clinical hemoperfusion material.     

Molecularly imprinted polymers as artificial steroid receptors

The polymers selective to six different steroids (testosterone, Δ⁴-androstene-3,17-dione, 1,4-androstadiene-3,17-dione, β-estradiol, progesterone, testosterone propionate) have been synthesized using molecular imprinting based on noncovalent interactions. Analysis of the influence of structural features of the steroids under study has shown that molecules with a relatively rigid structure and the OH group at C-17 position are the most efficient templates for methacrylic acid-containing imprinted polymers. The chromatographic study of the polymers synthesized has demonstrated a strong dependence of the selectivity and intensity of interaction with analytes on the composition of solvents used both as porogen and chromatographic mobile phase. To obtain polymers with highly selective recognition sites and to create the optimal conditions for molecular recognition, all possible interactions (between template and functional monomer, template and solvent, solvent and functional monomer) should be taken into account. <?TF="palat-i"> The batch rebinding study of testosterone by the imprinted polymer in acetonitrile has revealed some heterogeneity of recognition sites, and permitted determination of K_ass = 1.05 × 10⁴ M ⁻¹, ΔG° = −5.4 kcal/mol and N = 1.2 μmol/g for high-affinity sites and K_ass = 0.33 × 10⁴ M ⁻¹, ΔG° = −4.8 kcal/mol and N = 2.2 μmol/g for low-affinity sites. <?TF="palat-i"> The results obtained show how it is possible to regulate in different modes the molecular recognition by imprinted polymers as well as to fabricate polymers possessing the necessary properties depending on their practical application.© 1998 John Wiley & Sons, Ltd.     

Molecularly imprinted polymer based enantioselective sensing devices: A review

Chiral recognition is the fundamental property of many biological molecules and is a quite important field in pharmaceutical analysis because of the pharmacologically different activities of enantiomers in living systems. Enantio-differentiating signal of the sensor requires specific interaction between the chiral compounds (one or a mixture of enantiomers) in question and the selector. This type of interaction is controlled normally by at least three binding centers, whose mutual arrangement and interacting characteristics with one of the enantiomers effectively control the selectivity of recognition. Molecular imprinting technology provides a unique opportunity for the creation of three-dimensional cavities with tailored recognition properties. Over the past decade, this field has expanded considerably across the variety of disciplines, leading to novel transduction approaches and many potential applications. The state-of-art of molecularly imprinted polymer-based chiral recognition might set an exotic trend toward the development of chiral sensors. The objective of this review is to provide comprehensive knowledge and information to all researchers who are interested in exploiting molecular imprinting technology toward the rational design of chiral sensors operating on different transduction principles, ranging from electrochemical to piezoelectric, being used for the detection of chiral compounds as they pose significant impact on the understanding of the origin of life and all processes that occur in living organisms.     

Molecularly imprinted polymers for on-line clean up and preconcentration of chloramphenicol prior to its voltammetric determination

The performance of a molecularly imprinted polymer (MIP) as a selective solid-phase extraction sorbent for the clean-up and preconcentration of the antibiotic chloramphenicol is described. The MIP was prepared using chloramphenicol as the template, (diethylamino)ethyl methacrylate as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking monomer, and using tetrahydrofuran as the solvent. Detection of chloramphenicol was carried out by square-wave voltammetry at electrochemically activated carbon fiber microelectrodes. Chloramphenicol was eluted from the MIP microcolumn with methanol. Different experimental variables (sample pH, eluent volume, analyte and eluent flow rates and sample volume) associated with the rebinding/elution process were optimized. For a 250 mL sample, a nominal enrichment factor of 500 was attained, and for a chloramphenicol concentration of 3.0x10(-8) mol L(-1) (9.7 microg L(-1)) a recovery of 96+/-4% was obtained. A range of linearity for chloramphenicol between 3.0x10(-8) and 1.0x10(-5) mol L(-1) was obtained by loading 17 mL of analyte solutions of different concentration, eluting with 0.5 mL methanol, evaporating under a stream of nitrogen and dissolving the residue in phosphate buffer of pH 7.8. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of chloramphenicol. The applicability of the MIP for both clean up and preconcentration was demonstrated by determining chloramphenicol in ophthalmic solutions and spiked milk at different concentration levels.     

Molecularly imprinted polyaniline-polyvinyl sulphonic acid composite based sensor for para-nitrophenol detection

We report results of the studies relating to the fabrication and characterization of a conducting polymer based molecularly imprinted para-nitrophenol (PNP) sensor. A water pollutant, para-nitrophenol is electrochemically imprinted with polyvinyl sulphonic acid (PVSA) doped polyaniline onto indium tin oxide (ITO) glass substrate. This PNP imprinted electrode (PNPI-PANI-PVSA/ITO) prepared via chronopotentiometric polymerization and over-oxidation is characterized by Fourier transform infra-red spectroscopy (FT-IR), UV–visible (UV–vis) spectroscopy, contact angle (CA), scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies. The response studies of PNPI-PANI-PVSA/ITO electrode carried out using DPV reveal a lower detection limit of 1 × 10⁻³ mM, improved sensitivity as 1.5 × 10⁻³ A mM⁻¹ and stability of 45 days. The PNPI-PANI-PVSA/ITO electrode shows good precision with relative standard deviation of 2.1% and good reproducibility with standard deviation of 3.78%.     

Molecularly imprinted polymer nanocarriers for recognition and sustained release of diclofenac

In this study, a series of imprinted poly(methacrylic acid‐co‐ethylene glycol dimethacrylate) nanocarriers for diclofenac and corresponding nonimprinted polymer nanocarriers have been synthesized in 4 different types of solvents by precipitation polymerization. The products were characterized by Fourier transform infrared, scanning electron microscopy, dynamic light scattering, and Brunauer‐Emmett‐Teller measurement. Results showed that uniformly sized molecularly imprinted polymer (MIP) nanospheres with relatively good porosity could only be obtained in acetonitrile. The effects of solvents on the recognition and release properties of polymer particles were also carefully investigated. The binding experiments indicated that MIPs prepared in acetonitrile displayed much higher binding capacity than other MIPs with a maximum binding capacity of 65.18 mg g⁻¹. The Scatchard analysis showed that synthetic MIPs have special recognition sites for diclofenac, while nonimprinted polymers have not. The Sips model could provide a best fit to the equilibrium data of nanocarriers over whole concentrations. The experimental data of an adsorption kinetic study were well fitted to the pseudo–second‐order kinetic model, indicating the chemisorption mechanism between diclofenac and MIPs in the process of adsorption. The drug release of diclofenac from MIPs could well be described by the Ritger‐Peppas model, suggesting a non‐Fickian diffusion mechanism. In addition, we successfully used MIPs to extract diclofenac at low levels from fetal bovine serum.