Study of solvent effect on the synthesis of magnetic molecularly imprinted polymers based on ultrasound probe: Application for sulfonamide detection

Selective extraction of maleic hydrazide in foods using magnetic molecularly imprinted polymers and colorimetric detection via smartphone

Maleic hydrazide (MH) is a plant growth regulator, herbicide, and sprout inhibitor used to improve the growth and quality of certain vegetables and fruits, unfortunately, MH has genotoxic and carcinogenic effects; thus, MH residues in food need to be analyzed. Herein, magnetic molecularly imprinted polymers (MagMIP) were synthesized by radical polymerization in just 30 min using a microwave for rapid and selective extraction of MH. The colorimetric detection of MH using the immobilized Folin Ciocalteau's reagent (FCR) on 96-well microplate via smartphone sensor exhibits useful sensitivity for MH with a limit of detection (LOD = 0.6 ppm) which is far lower than the maximum residue limits (higher than 5 ppm). The immobilized FCR was stored dry at two different storage conditions at +4 °C and room temperature without losing its performance over six months. The coupling MagMIP-extraction/clean-up and smartphone determination were tested towards food samples (i.e., potatoes, and carrots), obtaining good recovery (79-96 %), high repeatability (RSD 4.5 %; n = 10), and high selectivity for MH determination.

Exploring the potential of molecularly imprinted polymers and metal/metal oxide nanoparticles in sensors: recent advancements and prospects

Metal/metal oxide nanoparticles have gained increasing attention in recent years due to their outstanding features, including optical and catalytic properties, as well as their excellent conductivity. The implementation of metal/metal oxide nanoparticles, combined with molecularly imprinted polymers (MIPs) has paved the way for a new generation of building blocks to engineer and enhance the fascinating features of advanced sensors. This review critically evaluates the impact of combining metal/metal oxide nanoparticles with MIPs in sensors. It covers synthesis strategies, advantages of coupling these materials with MIPs, and addresses questions about the selectivity of these hybrid materials. In the end, the current challenges and future perspectives of this field are discussed, with a particular focus on the potential applications of these hybrid composites in the sensor field. This review highlights the exciting opportunities of using metal/metal oxide nanoparticles along with MIPs for the development of next-generation sensors.

Unlocking the Potential of Molecularly Imprinted Polydopamine in Sensing Applications

Molecularly imprinted polymers (MIPs) are synthetic receptors that mimic the specificity of biological antibody-antigen interactions. By using a "lock and key" process, MIPs selectively bind to target molecules that were used as templates during polymerization. While MIPs are typically prepared using conventional monomers, such as methacrylic acid and acrylamide, contemporary advancements have pivoted towards the functional potential of dopamine as a novel monomer. The overreaching goal of the proposed review is to fully unlock the potential of molecularly imprinted polydopamine (MIPda) within the realm of cutting-edge sensing applications. This review embarks by shedding light on the intricate tapestry of materials harnessed in the meticulous crafting of MIPda, endowing them with tailored properties. Moreover, we will cover the diverse sensing applications of MIPda, including its use in the detection of ions, small molecules, epitopes, proteins, viruses, and bacteria. In addition, the main synthesis methods of MIPda, including self-polymerization and electropolymerization, will be thoroughly examined. Finally, we will examine the challenges and drawbacks associated with this research field, as well as the prospects for future developments. In its entirety, this review stands as a resolute guiding compass, illuminating the path for researchers and connoisseurs alike.

Determination of 35 sulfonamides in pork by magnetic molecularly imprinted polymer-based dispersive solid-phase extraction and ultra-performance liquid chromatography photodiode array method

BACKGROUND

Sulfonamide residues in foods of animal origin are potential risks to consumer health, so it is very important to inspect them. Among the previously reported instrumental methods, the best method can only be used to determine at most 22 sulfonamides. Thus, an instrumental method capable of determining more sulfonamide species is desirable.

RESULTS

In this study, sulfadoxine was used as a template to synthesize a type of magnetic molecularly imprinted polymer that could recognize 35 sulfonamides. After characterization, this composite was used to develop a dispersive solid-phase extraction method for extraction and purification of the 35 sulfonamides in pork, followed by determination using an ultra-performance liquid chromatography photodiode array method. This composite exhibited high adsorption capacity (11.01-19.21 μg mg^-1 ) and high recovery (>89.01%), and could be reused at least ten times. Due to the enrichment effect during sample preparation (enrichment factor 22-66), the limits of detection for determination of the 35 drugs in pork were in the range of 0.08-0.53 ng g^-1 . The detection results for some real pork samples were consistent with a liquid chromatographic-tandem mass spectrometric method. After comparison, the present method showed generally better performances than the previously reported sample preparation methods and instrumental methods for detection of sulfonamides.

CONCLUSION

The method developed in the present study could be used as a practical tool for routine detection of sulfonamide residues in pork samples. © 2022 Society of Chemical Industry.

State-of-the-art molecular imprinted colorimetric sensors and their on-site inspecting applications

Molecular imprinted colorimetric sensors can realize visual semi-quantitative analysis without the use of any equipment. With the advantages of low cost, fast response, ease of handling, and excellent recognition ability, the molecular imprinted colorimetric sensor shows great application potential in the field of sample rapid assay. Molecular imprinted colorimetric sensors can be prepared in various forms to meet the needs of different sample determination, such as film, hydrogel, strip, and adsorption coating. In this review, the preparation methods for various types of molecularly imprinted colorimetric sensors are systematically introduced. Their applications in the field of on-site biological sample detection, drug detection, disease treatment, chiral substance detection and separation, environmental analysis, and food safety detection are introduced. The limitations encountered in the practical application are presented, and the future development directions prospect.

Current Trends in Molecular Imprinting: Strategies, Applications and Determination of Target Molecules in Spain

Over the last decades, an increasing demand for new specific molecular recognition elements has emerged in order to improve analytical methods that have already been developed in order to reach the detection/quantification limits of target molecules. Molecularly imprinted polymers (MIPs) have molecular recognition abilities provided by the presence of a template molecule during their synthesis, and they are excellent materials with high selectivity for sample preparation. These synthetic polymers are relatively easy to prepare, and they can also be an excellent choice in the substitution of antibodies or enzymes in different kinds of assays. They have been properly applied to the development of chromatographic or solid-phase extraction methods and have also been successfully applied as electrochemical, piezoelectrical, and optical sensors, as well as in the catalysis process. Nevertheless, new formats of polymerization can also provide new applications for these materials. This paper provides a comprehensive comparison of the new challenges in molecular imprinting as materials of the future in Spain.

Study on Molecularly Imprinted Polymers Obtained Sonochemically for the Determination of Aflatoxins in Food

Aflatoxins (AFs) are fungi secondary metabolites produced by the Aspergillus family. These compounds can enter the food chain through food contamination, representing a risk to human health. Commercial immunoaffinity columns are widely used for the extraction and cleanup of AFs from food samples; however, their high cost and large solvent consumption create a need for alternative strategies. In this work, an alternative strategy for producing molecularly imprinted polymers (MIPs) was proposed to extract aflatoxins AFB1, AFB2, AFG1, and AFG2 from complex food samples, using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The MIPs were synthesized via a low-cost and rapid (5 min) sonochemical free-radical polymerization, using 1-hydroxy-2-naphthoic acid as a dummy template. MIPs-based solid phase extraction performance was tested on 17 dietary supplements (vegetables, fruits, and cereals), obtaining appreciable recovery rates (65-90%) and good reproducibility (RSD ≤ 6%, n = 3); the selectivity towards other mycotoxins was proved and the data obtained compared with commercial immunoaffinity columns. The proposed strategy can be considered an alternative affordable approach to the classical immunoaffinity columns, since it is more selective and better performing.

Factors Affecting the Analytical Performance of Magnetic Molecularly Imprinted Polymers

During the last few years, separation techniques using molecular imprinting polymers (MIPs) have been developed, making certain improvements using magnetic properties. Compared to MIP, Magnetic molecularly imprinted polymers (MMIPs) have high selectivity in sample pre-treatment and allow for fast and easy isolation of the target analyte. Its magnetic properties and good extraction performance depend on the MMIP synthesis step, which consists of 4 steps, namely magnetite manufacture, magnetic coating using modified components, polymerization and template desorption. This review discusses the factors that will affect the performance of MMIP as a selective sorbent at each stage. MMIP, using Fe₃O₄ as a magnetite core, showed strong superparamagnetism; it was prepared using the co-precipitation method using FeCl₃·6H₂O and FeCl₂·H₂O to obtain high magnetic properties, using NH₄OH solution added for higher crystallinity. In magnetite synthesis, the use of a higher temperature and reaction time will result in a larger nanoparticle size and high magnetization saturation, while a higher pH value will result in a smaller particle size. In the modification step, the use of high amounts of oleic acid results in smaller nanoparticles; furthermore, determining the correct molar ratio between FeCl₃ and the shielding agent will also result in smaller particles. The next factor is that the proper ratio of functional monomer, cross-linker and solvent will improve printing efficiency. Thus, it will produce MMIP with high selectivity in sample pre-treatment.

Enzyme inhibition coupled to molecularly imprinted polymers for acetazolamide determination in biological samples

Several methods involving molecularly imprinted polymers (MIPs) devoted to extracting and analyzing sulfonamides from different matrices are reported in literature; however, the unresolved analytical issue is obtaining intra-class selectivity between sulfonamides. Here is presented for the first time a method coupling MIPs and enzymatic inhibition assay for the sensitive and selective determination of acetazolamide (ACZ) in biological samples. The MIPs were synthesized by thermal initiated polymerization in acetone, using acrylamide as functional monomer, ethylene glycol dimethacrylate as cross-linker and ACZ as template molecule. The developed MIPs/enzymatic inhibition based rapid colorimetric method was applied for the determination of ACZ in biological samples. The MIPs were used as sorbent phase in dispersive solid-phase extraction (MIPs-dSPE), and the optimal working parameters were selected. Liquid chromatography-tandam mass spectrometry (LC-MS/MS) analysis confirmed the MIPs ability to extract ACZ. Finally, to obtain a selective and sensitive method, the MIPs-dSPE was combined with an enzymatic inhibition colorimetric assay based on the carbonic anhydrase, an enzyme inhibited by specific sulfonamides. The developed combined method allowed the determination of ACZ in serum, blood and Diamox (a drug containing ACZ), with good recovery (85-96%). Furthermore, a significant correlation with LC-MS/MS analysis was achieved, with relative error ≤15%. In the proposed strategy, the double selectivity giving by MIPs and enzymatic inhibition allowed to obtain a method able to determine selectively ACZ in biological and pharmaceutical samples quantitatively.

Molecularly Imprinted Polymers Combined with Electrochemical Sensors for Food Contaminants Analysis

Detection of relevant contaminants using screening approaches is a key issue to ensure food safety and respect for the regulatory limits established. Electrochemical sensors present several advantages such as rapidity; ease of use; possibility of on-site analysis and low cost. The lack of selectivity for electrochemical sensors working in complex samples as food may be overcome by coupling them with molecularly imprinted polymers (MIPs). MIPs are synthetic materials that mimic biological receptors and are produced by the polymerization of functional monomers in presence of a target analyte. This paper critically reviews and discusses the recent progress in MIP-based electrochemical sensors for food safety. A brief introduction on MIPs and electrochemical sensors is given; followed by a discussion of the recent achievements for various MIPs-based electrochemical sensors for food contaminants analysis. Both electropolymerization and chemical synthesis of MIP-based electrochemical sensing are discussed as well as the relevant applications of MIPs used in sample preparation and then coupled to electrochemical analysis. Future perspectives and challenges have been eventually given.

Fast microwave-assisted synthesis of magnetic molecularly imprinted polymer for sulfamethoxazole

A fast and simple strategy based on the microwave technique for the preparation of magnetic molecularly imprinted polymers (MMIPs) is proposed for the selective determination of sulfamethoxazole (SMX). The MMIPs were synthesized at 70 °C in 20 min, being much faster than the conventional techniques. A computational approach based on density functional theory was used to design the MMIP and compare the two most used monomers in MIPs, including methacrylic acid (MAA) and acrylamide (AM). Then, two different MMIPs were prepared using AM and MAA as monomers. The resultant materials were characterized with X-ray diffraction, thermogravimetric analysis, scanning/transmission electron microscopy, and Fourier-transform infrared spectroscopy. Besides, the adsorption characterizations suggested that the adsorption of SMX followed the pseudo-second-order model in the kinetic study and the Sips model in the isotherm study. The experimental results corroborated the computational approach. Furthermore, Both MMIPs demonstrated good selectivity. The MMIP-AM and MMIP-MAA were applied as adsorbents in magnetic dispersive solid-phase extraction combined with UV-visible spectroscopy to quantify SMX. The obtained limits of detection and quantification were lower than 0.59 and 1.77 μM, respectively for both MMIPs. The sensitivity of both MMIPs was in the range of 0.021-0.023 (SI). Our findings revealed that there is no significant difference in the analytical parameters between MMIP-AM and MMIP-MAA. However, the application of both MMIPs in a real sample (tap water) showed that the recovery values of SMX obtained with MMIP-AM (68-70%) were lower than that with MMIP-MAA (80-90%) suggesting that MMIP-MAA is more appropriate for SMX determination.

A new approach for microextraction of trace albendazole sulfoxide drug from the samples of human plasma and urine, and water by the molecularly imprinted polymer nanoparticles combined with HPLC

In this research study, a method of dispersive-micro-solid phase extraction (D-µ-SPE) combined with molecularly imprinted polymer nanoparticles (MIP-NPs) with HPLC-UV was developed for the fast and selective detection of the trace amount of albendazole sulfoxide (ABZSO) in the biological samples. To investigate the effective factors on ABZSO microextraction by the method, central composite design (CCD) was utilized, and the optimum conditions for ABZSO microextraction were sample pH of 8.0, MIP-mass of 15 mg, sonication time of 12 min, and eluent (methanol) volume of 0.25 mL. Under the obtained optimal extraction conditions, the value for the limit of detection (LOD) and limit of quantification (LOQ) was respectively showed to be 0.074 and 0.246 ng mL^-1. In addition, the calculated peak areas exhibited a linear relationship with the ABZSO concentration ranging from 0.4 to 4200 ng mL^-1. The analyses of the samples including human plasma and urine, and water were successfully performed by the usage of the D-µ-SPE method, which was a simple and sensitive technique and a suitable alternative for the analysis of ABZSO. In the analysis of ABZSO in various samples, the recoveries at various levels of ABZSO concentrations (50, 300, and 500 ng mL^-1) were in the range of 95.7-103.0 %, and the relative standard deviations (RSDs; n = 3) varied from 2.2 to 4.4%.

Highly Selective Fluorescence Sensor Based on Graphene Quantum Dots for Sulfamethoxazole Determination

In our research, a reliable fluorescence sensor for the detection of sulfamethoxazole (SMZ) was developed. This method relies on graphene quantum dots (GQDs) entrapped in a silica molecularly imprinted polymer (GQDs@SMIP), which was synthesized by the polymerization using GQDs, SMZ, tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as fluorescence material, template, cross-linker, and functional monomers, respectively. The GQDs@SMIP was characterized by fluorometry, Fourier-transform infrared spectroscopy, transmission and scanning electron microscopies, X-ray photoelectron spectroscopy, and powder X-ray diffraction. The GQDs@SMIP exhibited a good capacity to absorb SMZ from solution, which resulted in the quenching of the GQD fluorescence intensity. The intensity of GQDs@SMIP decreased linearly with the SMZ concentration in the range of 1 to 100 µM with a correlation coefficient of 0.99537. In addition, the fluorescence responses of GQDs@SMIP to interfering substances were investigated. The results indicated that there was no effect of interfering substances on SMZ detection. Thus, the highly selective GQDs@SMIP fluorescence sensor is an effective and promising device for SMZ detection and analysis.

Magnetic molecularly imprinted electrochemical sensors: A review

The preparation and practical applications of molecularly imprinted electrochemical sensors (MIECSs) remain challenging due to issues involving electrode surface renewal modes, low adsorption capacities, and sample preparation speeds. To solve these issues, magnetic molecularly imprinted electrochemical sensors (MMIECSs) have been extensively explored by various groups. Recently, MMIECSs fabricated based on diverse strategies have yielded insight into the development of MIECSs, and they have provided effective paths for sample preparation, immobilization and renewal of molecularly imprinted polymers (MIPs) on the electrode surface, leading to promising performances of MIECSs. This review comprehensively describes the research advances for various types of MMIECSs and their applications in the fields of food safety, environmental monitoring, and clinical and pharmaceutical analysis. Based on our understanding of MMIECSs, the literature in this field is thoroughly explored and classified in this review. The challenges existing in this research area and some potential strategies for the rational design of high-performance MMIECS are also outlined.