Fabrication of a molecularly imprinted polymer-based electrochemical sensor for the selective assay of antipsychotic drug clozapine and performance comparison with LC-MS/MS

Clozapine (CLO) is an atypical antipsychotic drug indicated for the treatment of schizophrenia. The treatment effectiveness of CLO is better than that of other atypical antipsychotics, and it has the advantage of being able to determine its effectiveness by measuring its concentration in the patient's blood. Thus, sensitive, selective, and accurate determination of CLO in blood is highly significant for treatment monitoring. This study describes the design and fabrication of a molecularly imprinted polymer (MIP)-based electrochemical sensor for CLO determination. This is the first MIP-based electrochemical application in the literature for CLO determination. Employing the thermal polymerization approach, the MIP was formed on the glassy carbon electrode (GCE) using CLO as the template, trans-3-(3-Pyridyl)acrylic acid (3,3-TA) as the functional monomer, and the support of zinc oxide nanoparticles (ZnO NPs). Elaborate characterizations in terms of surface morphology and electrochemistry were performed via scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods. An indirect approach was employed to determine CLO in standard solution, real human biological samples, and tablet formulation, using 5 × 10-3 M [Fe(CN)6]3-/4- solution as the redox probe. The limit of detection (LOD) values for the standard solution and serum sample were calculated as 2.9 × 10-11 M and 6.01 × 10-12 M, respectively. These values and recovery studies confirmed the sensor's sensitivity and feasibility. The measurements in the presence of similarly structured compounds (olanzapine and quetiapine fumarate) verified the sensor's superior selectivity. Moreover, the developed sensor's performance was compared and verified using an LC-MS/MS method using the student's t-test and F-test.

Preparation and optimization of dummy molecularly imprinted polymer-based solid-phase extraction system for selective enrichment of p-toluene sulfonate esters genotoxic impurities

Sulfonate esters, one class of genotoxic impurities (GTIs), have gained significant attention in recent years due to their potential to cause genetic mutations and cancer. In the current study, we employed the dummy template molecular imprinting technology with a dummy template molecule replacing the target molecule to establish a pretreatment method for samples containing p-toluene sulfonate esters. Through computer simulation and ultraviolet-visible spectroscopy analysis, the optimal functional monomer acrylamide and polymerization solvent chloroform were selected. Subsequently, a dummy template molecularly imprinted polymer (DMIP) was prepared by the precipitation polymerization method, and the polymer was characterized in morphology, particle size, and composition. The results of the adsorption and enrichment study demonstrated that the DMIP has high adsorption capability (Q = 7.88 mg/g) and favorable imprinting effects (IF = 1.37); Further, it could simultaneously adsorb three p-toluene sulfonate esters. The optimal adsorption conditions were obtained by conditional optimization of solid-phase extraction (SPE). A pH 7 solution was selected as the loading condition, the methanol/1 % phosphoric acid solution (20:80, v/v) was selected as the washing solution, and acetonitrile containing 10 % acetic acid in 6 mL was selected as the elution solvent. Finally, we determined methyl p-toluene sulfonate alkyl esters, ethyl p-toluene sulfonate alkyl esters, and isopropyl p-toluene sulfonate alkyl esters in tosufloxacin toluene sulfonate and capecitabine at the 10 ppm level (relative to 1 mg/mL active pharmaceutical ingredient (API) samples) by using DMIP-based SPE coupled with HPLC. This approach facilitated the selective enrichment of p-toluene sulfonate esters GTIs from complex API samples.

A probe of new molecularly imprinted solid-phase extraction coupled with HPLC-DAD and atomic absorption spectrophotometry for quantification of tetracycline HCl, metronidazole and bismuth subcitrate in combination with their official impurities: Application in dosage form and human plasma

The integration of molecular imprinting technique with chromatographic one has a great impact on the assay's selectivity and sensitivity. Herein, a molecularly imprinted solid-phase extraction associated with high performance liquid chromatography (MISPE-HPLC) was employed for simultaneous determination of the co-formulated drugs; tetracycline hydrochloride (TET) and metronidazole (MET), in plasma and in their anti-H-pylori drug for the first time. Two sorts of molecularly imprinted polymers (MIPs) were fabricated using TET and MET as the template molecules, while ethylene glycol dimethacrylate and methacrylic acid were used as a cross-linker and a monomer, respectively. The synthesized MIPs were identified using different techniques. The adsorption-desorption capability of each template was investigated towards its corresponding MIP. The extraction conditions of MISPE was optimized with respect to TET/MIP and MET/MIP sorbent. Bismuth subcitrate (BSC), the third co-formulated drug was analyzed in spiked human plasma using an atomic absorption spectrometric (AAS) method. The performance of the developed methods was assured as per ICH guidelines for analyzing the studied drugs in their pharmaceutical dosage form along with two of their official impurities. In addition, bioanalytical method validation was conducted where linearity was achieved at 2.0-40.0 μg mL-1, 2.0-40.0 μg mL-1 and 5.0-80.0 μg mL-1 for TET, MET and BSC, respectively.

Molecular imprinted polymer-based potentiometric approach for the assay of the co-formulated tetracycline HCl, metronidazole and bismuth subcitrate in capsules and spiked human plasma

BACKGROUND

An anti-H-pylori co-formulated mixture of tetracycline HCl (TET), metronidazole (MET), and bismuth subcitrate (BSC) is recently available. Only two chromatographic and spectrophotometric methods are reported for determining those drugs simultaneously where the effect of impurities that could be present as well as the biological fluids matrix influence do not be taken into consideration. There is a need to develop an easy-to-use potentiometric technique for analysis of TET, MET, and BSC in their co-formulated capsules, in presence of some official impurities and in spiked human plasma.

RESULTS

Three carbon paste electrodes (CPEs) were fabricated for this purpose. Being a solid contact ion-selective electrode, CPE suffers from the creation of a water layer affecting its stability and reproducibility. Besides, it has a common problem in differentiation between two drugs carrying the same charge (positively charged TET and MET). Water layer formation was prevented through inserting polyaniline nanoparticles (≈10.0 nm diameter) between solid contact and ion-sensing membrane in the three proposed sensors. TET and MET interference was overcome by synthesizing a corresponding molecular imprinted polymer (MIP) for each drug. The synthesized MIPs were inserted in equivalent sensing membranes and characterized using several techniques. The suggested MIPs have a noticeable enhanced sensitivity in potentiometric determination. The obtained LODs were 5.88 × 10-8, 5.19 × 10-7, and 1.73 × 10-6 M for TET, MET and BSC proposed CPEs, respectively, with corresponding slopes of 57.37, 56.20, and -57.40 mV decade-1.

SIGNIFICANCE

The proposed potentiometric method makes the detection of the three cited drugs simple, fast, and feasible. This approach is the first for determining three drugs potentiometrically in one combined formulation. The obtained results were compared favorably with previously reported potentiometric methods.

Development and Characterization of a Molecularly Imprinted Polymer for the Selective Removal of Brilliant Green Textile Dye from River and Textile Industry Effluents

In this paper, we present an alternative technique for the removal of Brilliant Green dye (BG) in aqueous solutions based on the application of molecularly imprinted polymer (MIP) as a selective adsorbent for BG. The MIP was prepared by bulk radical polymerization using BG as the template; methacrylic acid (MAA) as the functional monomer, selected via computer simulations; ethylene glycol dimethacrylate (EGDMA) as cross-linker; and 2,2'-azobis(2-methylpropionitrile) (AIBN) as the radical initiator. Scanning electron microscopy (SEM) analyses of the MIP and non-molecularly imprinted polymer (NIP)-used as the control material-showed that the two polymers exhibited similar morphology in terms of shape and size; however, N2 sorption studies showed that the MIP displayed a much higher BET surface (three times bigger) compared to the NIP, which is clearly indicative of the adequate formation of porosity in the former. The data obtained from FTIR analysis indicated the successful formation of imprinted polymer based on the experimental procedure applied. Kinetic adsorption studies revealed that the data fitted quite well with a pseudo-second order kinetic model. The BG adsorption isotherm was effectively described by the Langmuir isotherm model. The proposed MIP exhibited high selectivity toward BG in the presence of other interfering dyes due to the presence of specific recognition sites (IF = 2.53) on its high specific surface area (112 m2/g). The imprinted polymer also displayed a great potential when applied for the selective removal of BG in real river water samples, with recovery ranging from 99 to 101%.

Molecularly Imprinted Polymeric Particles Created Using Droplet-Based Microfluidics: Preparation and Applications

Recent years have witnessed increased attention to the use of droplet-based microfluidics as a tool for the fabrication of microparticles due to this method's ability to exploit fluid mechanics to create materials with a narrow range of sizes. In addition, this approach offers a controllable way to configure the composition of the resulting micro/nanomaterials. To date, molecularly imprinted polymers (MIPs) in particle form have been prepared using various polymerization methods for several applications in biology and chemistry. However, the traditional approach, that is, the production of microparticles through grinding and sieving, generally leads to poor control over particle size and distribution. Droplet-based microfluidics offers an attractive alternative for the fabrication of molecularly imprinted microparticles. This mini-review aims to present recent examples highlighting the application of droplet-based microfluidics to fabricate molecularly imprinted polymeric particles for applications in the chemical and biomedical sciences.

Formation, Analytical Methods, Change Tendency, and Control Strategies of Biogenic Amines in Canned Aquatic Products: A Systematic Review

ABSTRACT

Biogenic amines (BAs) are organic compounds with low molecular weight and can be used as indicators of the quality and safety of canned aquatic products during processing and storage. However, excess of these amines can cause foodborne poisoning. Therefore, the determination, analysis, and prevention of BAs are of great importance. This article focuses on the sources, formation, and pretreatment methods, as well as analytical techniques, change tendency, and control techniques of BAs, with the aim of promoting more appropriate analysis of canned aquatic products to provide a reference for the food industries.

HIGHLIGHTS

Solid-Phase Extraction of Active Compounds from Natural Products by Molecularly Imprinted Polymers: Synthesis and Extraction Parameters

Molecularly imprinted polymers (MIPs) are synthetic polymers with a predetermined selectivity for a particular analyte or group of structurally related compounds, making them ideal materials for separation processes. Hence, in sample preparation, MIPs are chosen as an excellent material to provide selectivity. Moreover, its use in solid-phase extraction, also referred to as molecular imprinted solid phase extraction (MISPE), is well regarded. In recent years, many papers have been published addressing the utilization of MIPs or MISPE as sorbents in natural product applications, such as synthesis. This review describes the synthesis and characterization of MIPs as a tool in natural product applications.

Microsphere molecularly imprinted solid-phase extraction for diazepam analysis using itaconic acid as a monomer in propanol

Diazepam (DZP) is a benzodiazepine drug used as an anti-drug and sedative. It is often misused to induce or create euphoria in combination with other drugs (high or fly sensation) or administered alone. So far, screening for DZP abuse with sensitive analytical methods is needed, as its small concentrations make it difficult to detect. Increased sensitivity of the analytical method can be obtained by using a preparation method that selectively separates the analyte from the sample matrix. Molecularly imprinted polymer (MIP) is one of the preparation solutions with good selectivity, specificity, and sensitivity. MIP was made from DZP as a template, itaconic acid, and ethylene glycol dimethacrylate in a composition of 1:4:20. MIP was made by precipitation polymerisation to obtain microsphere polymer type. MIP had a binding capacity value of 0.0557 mg/g and followed the Freundlich isotherm. Application of the microsphere MIP on spiked blood serum resulted in a recovery of 105.63 ± 1.0% for MIP compared to 21.28 ± 0.4% for non-imprinted polymer, with the imprinting factor value reaching 4.96. Hence, MIP DZP with itaconic acid as a functional monomer and propanol as a porogen, fabricated by the precipitation polymerisation method, is a promising sorbent for DZP extraction in biological fluids.

Computer simulation aided preparation of molecularly imprinted polymers for separation of bilobalide

In this study, the preparation of molecularly imprinted polymers for bilobalide (BBMIPs) was successfully achieved by bulk polymerization with methacrylamide (MAM), trimethylolpropane triacrylate (TMPTA), and acetonitrile (ACN) as functional monomer, cross-linker, and solvent, respectively. After Gaussian software simulation and single factor experiments, the prepared MIPs with a molar ratio of 1:4:15 for BB-MAM-TMPTA were systematically characterized. The hydrogen bonding interaction between BB and MAM was confirmed by a combination of FTIR and NMR analysis. Thermal gravimetric analysis results displayed that MIPs have excellent thermal stability under high temperature. Additionally, the average pore size and surface area of MIPs were found to be higher than those of NIPs through nitrogen adsorption results. The results of static adsorption and kinetic adsorption suggested that the adsorption equilibrium concentration was 0.6 mg/mL and the equilibrium time was 5 h, and the Langmuir and pseudo-second-order kinetic models were proven to fit with static and kinetic adsorption behaviors, respectively. Meanwhile, the selective adsorption study revealed that MIPs show high adsorption and great selectivity towards BB in comparison with other substances having similarly structure. MIPs also possessed a good performance on reusability, maintaining a high recovery rate after being reused 5 times. The application experiment further indicated that MIPs can effectively separate BB from low purity samples. Therefore, the prepared MIPs had a great potential for BB separation.

Preparation and Characterization of Herbicide Mecoprop Imprinted Polymer and Its Application as a Selective Sorbent in Water Sample

Bulk polymerization method was used to prepare a homogeneous molecularly imprinted polymer (MIP) for the specific extraction of herbicide mecoprop (MCPP). Thereafter, the binding performance of this functional polymer was evaluated under optimal condition, compared to a non-imprinted polymer. From the Scatchard plot analysis, two types of binding sites were detected in the MIP, the high affinity binding sites with a K_D (equilibrium dissociation constant) of 6.4 µM and the low affinity ones with a K_D of 55.9 µM. In addition, the possibility of using synthesized MIP for MCPP extraction from environmental aqueous samples was explored. The adsorption capacity of MIP in spiked bottled water and groundwater samples showed that the polymer could effectively extract MCPP from bottled water and groundwater (p < 0.05) with the recovery of 70.5% and 65.1%, respectively, demonstrating the potential of imprinted polymers for cost-effective and effective water treatment.

Assessment of the imprinting efficiency of an imide with a "stoichiometric" pyridine-based functional monomer in precipitation polymerisation

The efficiency of the stoichiometric non-covalent imprinting of the imide 2,3,5-tri-O-acetyluridine (TAU) with 2,6-bis(acrylamido)pyridine (BAAPy) as functional monomer due to their strong donor-acceptor-donor/acceptor-donor-acceptor (DAD/ADA) hydrogen bond array interaction has been evaluated by bulk imprinting. This study is the first to investigate the imprinting and template rebinding efficiencies of the TAU/BAAPy molecularly imprinted polymeric (MIP) system prepared by precipitation polymerisation. We found that the stoichiometric 1:1 T:FM ratio has not been maintained in precipitation polymerisation and an optimal TAU:BAAPy ratio of 1:2.5 was obtained in acetonitrile without agitation affording an affinity constant (1.7 × 10⁴ M^-1 ) and a binding capacity (3.69 μmol/g) higher than its bulk counterpart. Molecular modelling, NMR studies, and selectivity assays against analogues uridine and 2,3,5-tri-O-acetyl cytidine (TAC) indicate that, aside from the DAD/ADA hydrogen bond interaction, BAAPy also interacts with the acetyl groups of TAU. Template incorporation and rebinding in precipitation MIPs are favoured by a moderate initiator concentration, ie, initiator:total monomer (I:TM) ratio of 1:131, while low I:TM ratio (ie, 1:200) drastically reduced template incorporation and binding capacity. Vigorous agitation by stirring showed higher template incorporation but significantly lower template rebinding compared to that prepared without agitation. While the imprinting efficiencies for the best performing bulk and precipitation TAU MIPs generated in this study were moderate, 41% and 60%, respectively, their rebinding capacities were only between 3 and 4% of the incorporated template. We also present quantitative nuclear magnetic resonance spectroscopy as an efficient method for MIP characterisation.

Precipitation polymerization: a versatile tool for preparing molecularly imprinted polymer beads for chromatography applications

Minireview on recent advances of application of MIPs prepared by precipitation polymerization for recognition of target analytes in complex matrices.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Preparation and study of tramadol imprinted micro-and nanoparticles by precipitation polymerization: microwave irradiation and conventional heating method

In the present work a series of tramadole imprinted micro- and nanoparticles were prepared and study their recognition properties. Methacrylic acid (MAA), as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker and different solvents (chloroform, toluene and acetonitrile (ACN)) were used for the preparation of molecularly imprinted polymers (MIPs) and non-imprinted polymers (NIPs). Several factors such as template/monomer molar ratio, volume of polymerization solvent, total monomers/solvent volume ratio, polymerization condition (heating or microwave irradiation) were also investigated. Particle size of the polymers, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), rebinding, selectivity tests and release study were applied for evaluation of the polymers. The optimized polymers with smaller particle size and superior binding properties were obtained in acetonitrile under heating method. MIPA4 with a size of 42.6 nm and a binding factor (BF) of 6.79 was selected for selectivity and release tests. The polymerization was not successful in acetonitrile and toluene under microwave irradiation. The MIPA4 could selectively adsorb tramadol, compared to imipramine, naltrexone and gabapentin. The data showed that tramadol release from MIPA4 was significantly slower than that of its non-imprinted polymer. Therefore, MIP nanoparticles with high selectivity, binding capacity and ability to control tramadol release could be obtained in precipitation polymerization with optimized condition.

Application of molecularly imprinted hydrogel for the preparation of lactose-free milk

BACKGROUND

A variety of lactose imprinted hydrogels were prepared and their binding properties were studied in comparison with blank non-imprinted hydrogel. Methacrylamide and ethylene glycol dimethacrylate were used as functional monomer and cross-linker, respectively. Dimethylsulfoxide was also applied as polymerisation solvent.

RESULTS

Different template/monomer ratios were studied and the optimised imprinted hydrogel (MIP₂), with a lactose/methacrylamide ratio of 1:8, was selected in a rebinding test. In Scatchard analysis of MIP₂-lactose interactions, the dissociation constant and maximum binding sites were 0.33 mmol L⁻¹ and 67.76 µmol g⁻¹ hydrogel, respectively. The selectivity of MIP₂ for lactose in aqueous media was also evaluated in comparison with different mono- and disaccharides. The data showed that the affinity of MIP₂ for lactose is significantly higher than other saccharides. The imprinted hydrogel was finally used as a sorbent for separation of lactose from milk.

CONCLUSIONS

The results indicated that MIP₂, as an optimised imprinted hydrogel, can effectively bind lactose and decrease its concentration in milk.

Study on the Weakest Interaction Model for Chiral Resolution Using Molecularly Imprinted Polymer

Molecularly imprinted polymers (MIPs) of L-phenylalanine ethyl ester were synthesized in this study. Then, the prepared MIPs were packed in a stainless column and evaluated as the chiral stationary phases of high performance liquid chromatography (HPLC). The MIPs exhibited a considerable capability of chiral separation between template molecule and its enantiomer with the separation factor of 1.69. Furthermore, the weakest interaction model was introduced to study the chiral recognition mechanism of MIPs. The results suggested that the weakest interaction between the template molecule and the imprinted cavity played crucial role in chiral separation, and the molecular tension should be taken into consideration during the separation procedure. The separation factor of 2.07 was calculated by the theoretical model, which was very close to the value obtained from chromatographic experiment.