Stimuli-responsive molecularly imprinted polymers as adsorbents of analytes in complex matrices

Core-shell molecularly imprinted polymers for the monitoring of dimethyl phthalate in the children's toys1

Plastic materials contain many additives, among which plasticizers from the group of phthalates are added during the production of everyday products, including children's toys. Even if the European Union and many other regions, for example Canada and the United States, have established restrictions on phthalate esters in children's toys or food contact materials and electronic and electrical products, there is still a danger that products imported from regions where there are no such restrictions can contain these dangerous compounds belonging to the group of endocrine disruptors. The additives introduced into plastics are not chemically bound to the polymer chain, so they can easily migrate to the external environment. This paper presents the process of synthesis of the core-shell type of molecularly imprinted polymers (MIPs) toward dimethyl phthalate (DMP). The most suitable polymerization mixture, which was selected to obtain the MIP layer, was prepared from the 4:6 wt ratio of methyl methacrylate and ethylene glycol dimethacrylate in the n-octane environment and with the addition of 5 wt% of the template. This material was characterized with the highest value of DMP removal, the maximum sorption capacity of this thin layer of MIP was about 3.0 mg/L. Additionally, DMP was about 3 times and about 5 times more efficient sorbed by core-shell MIP, than diethyl phthalate (DEP) and dibutyl phthalate (DBP), respectively. The best sorbed core-shell molecularly imprinted polymer was used as a column filler for solid phase extraction and was used to identify the phthalates present from rubber duck extraction solutions, showing the presence of this compound in the analyzed samples. The method developed in this work has a low limit of detection (LOD) and a low limit of quantification (LOQ) and a wide linear range, allowing DMP to be determined at both at trace levels (0.151 mg/L) and at higher concentrations.

Recent advances in molecular-imprinting-based solid-phase microextraction for determination of pharmaceutical residues

Pharmaceutical residues usually exist in various complicated matrices at trace levels, but pose potential threats to human health and ecological environment. Recognition and determination of the residues are important and urgent. Therefore, efficient sample pretreatment techniques become a research hotspot for the sensitive and precise determination by chromatography and mass spectrometry. Molecular-imprinting-based solid-phase microextraction (MI-SPME) combines the rapidity, high enrichment and solvent-free property of SPME with the specific recognition and selective adsorption ability of molecularly imprinted polymers (MIPs), and shows significant advantages in the highly selective separation and enrichment of drug residues in complex samples. Herein, we review recent advances in MI-SPME for determination of pharmaceutical residues since 2019. Firstly, the basic characteristics and operation process of SPME are briefly introduced, and then the polymerization methods of MIPs including free radical polymerization, in-situ polymerization and sol-gel polymerization, and new imprinting technologies and strategies including surface imprinting, nano-imprinting, dummy template, multi-template/functional monomer imprinting and stimuli-responsive imprinting, are comprehensively overviewed. Then, various modes of MI-SPME device are meticulously discussed, mainly including MIPs-coated fiber SPME, MIPs-based in-tube SPME, dispersible SPME, MIPs in-tip SPME, MIPs stir bar sorptive extraction, and MIPs thin film microextraction. Subsequently, typical application cases of MI-SPME coupled with chromatography and mass spectrometry for the determination of drug residues are summarized, in the fields of food safety, biological medicine and environmental monitoring, specially mentioning chiral drug detection and matrix effects and interferences. Finally, the possible challenges of MI-SPME in drug residue detection are presented, and the research prospects and development trends of MI-SPME are proposed.

Preparation of Temperature-Sensitive Molecularly Imprinted Cryogel for Specific Recognition of Proteins

In order to maintain the stability of the structure of protein molecules and improve the recognition during the separation process, molecular imprinting technology is combined with freeze polymerization to synthesize molecular imprinting cryogels (MICs). This study uses bovine serum albumin (BSA) as a template protein, low critical cosolubility temperature (LCST)-type ionic liquids as temperature-sensitive functional monomers, imidazole ionic liquids, and acrylamides as auxiliary functional monomers to prepare MICs with specific recognition, temperature sensitivity, interpenetrating macroporous structure, and large specific surface area. The MICs prepared at freezing temperature have uniform macroporous structures and good mechanical properties, which is conducive to the improvement of the mass transfer and adsorption capacities. Due to the advantages, the MIC reaches the adsorption equilibrium within 125 min with a saturated adsorption capacity of 741.5 mg g-1 and an imprinting factor of 1.65. Their static and dynamic adsorption behaviors are more in line with the Langmuir model and the quasi-secondary kinetic model, respectively. In addition, the MIC has obvious temperature sensitivity, and the maximum adsorption amount is reached at 37 °C. The separation factor (relative to cytochrome c, bovine blood hemoglobin, and lysozyme) of the MICs for BSA is up to 1.39. Repeatability experiments reveal that the adsorption capacity of molecularly imprinted cryogels is retained at 87% after five adsorption-desorption cycles, indicating excellent recyclability and potential for practical application.

Tuning the properties of peptide imprinted nanoparticles for protein immunoprecipitation using magnetic streptavidin beads

Maximizing the binding properties of thermoresponsive molecularly imprinted nanoparticles (MIN) was aimed to explore their feasibility as antibody substitutes in protein immunoprecipitation (IPP) with magnetic streptavidin beads (MSB). Thermoresponsive MIN targeting the cannabinoid CB1 receptor were produced by epitope imprinting through solid-phase synthesis. It was intended to determine how different variables influenced physicochemical features, binding behaviour and immunoprecipitation of the target recombinant glutathione S-transferase tagged fusion protein (GST-CTer). Such variables included the cross-linking degree of MIN, and variables like pH, temperature or the use of Tween-20 for binding and IPP experiments. The cross-linker (CL) amount influenced the coil-to-globule transition of thermoresponsive MIN, making the lower critical solution temperature (LCST) decrease from 37.2 °C using 5% of CL, to 29.0 °C using 25%, also suggesting higher plasticity on the former. Temperature influence on size was corroborated by dynamic light scattering, observing size reductions from 250-450 nm (RT) to 70-100 nm (> LCST) for MIN produced with 5-15% of CL. However, binding behaviour did not clearly  improve for more than 10% CL. Further experiments revealed that temperature and pH control were critical for efficient binding and release, selecting 40 °C and pH 5 as appropriate. Following binding experiments, the GST-CTer-MIN complex was successfully immunoprecipitated using MSB, achieving an IPP efficiency of 11.48% over the initial input protein concentration, which was calculated after SDS-PAGE separation and Western blot analysis. The methodology may be exploited for selective protein extraction and quantification from complex tissue homogenates.

Green Synthesis of Molecularly Imprinted Polymers for Selective Extraction of Protocatechuic Acid from Mango Juice

A novel and environmentally friendly molecularly imprinted polymer (PCA-MIP) was successfully synthesized in an aqueous solution for the selective extraction of protocatechuic acid (PCA). In this study, a deep eutectic solvent (DES, choline chloride/methacrylic acid, 1:2, mol/mol) and chitosan were employed as the eco-friendly functional monomers. These two components interacted with PCA through hydrogen bonding, integrating a multitude of recognition sites within the PCA-MIP. Thus, the resulting PCA-MIP exhibited outstanding adsorption performance, rapid adsorption rate, and better selectivity, with a maximum binding capacity of 30.56 mg/g and an equilibrium time of 30 min. The scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) analyses revealed that the synthesized polymers possessed a uniform morphology and substantial surface areas, which were conducive to their adsorption properties. Moreover, the PCA-MIP integrated with HPLC demonstrated its efficacy as an adsorbent for the selective extraction of PCA from mango juice. The PCA-MIP presented itself as an exemplary adsorbent, offering a highly effective and eco-friendly method for the enrichment of PCA from complex matrices.

Recent advances in the removal of emerging contaminants from water by novel molecularly imprinted materials in advanced oxidation processes-A review

Recently, there has been a global focus on effectively treating emerging contaminants (ECs) in water bodies. Advanced oxidation processes (AOPs) are the primary technology used for ECs removal. However, the low concentrations of ECs make it difficult to overcome the interference of background substances in complex water quality, which limits the practical application of AOPs. To address this limitation, many researchers are developing new catalysts with preferential adsorption. Molecular imprinting technology (MIT) combined with conventional catalysts has been found to effectively enhance the selectivity of catalysts for the targeted catalytic degradation of pollutants. This review presents a comprehensive summary of the progress made in research on molecularly imprinted polymers (MIPs) in the selective oxidation of ECs in water. The preparation methods, principles, and control points of novel MIP catalysts are discussed. Furthermore, the performance and mechanism of the catalysts in photocatalytic oxidation, electrocatalytic oxidation, and persulfate activation are analyzed with examples. The possible ecotoxicological risks of MIP catalysts are also discussed. Finally, the challenges and prospects of applying MIP catalysts in AOP are presented along with proposed solutions. This review provides a better understanding of using MIP catalysts in AOPs to target the degradation of ECs.

A Fusion of Molecular Imprinting Technology and Siloxane Chemistry: A Way to Advanced Hybrid Nanomaterials

Molecular imprinting technology is a well-known strategy to synthesize materials with a predetermined specificity. For fifty years, the "classical" approach assumed the creation of "memory sites" in the organic polymer matrix by a template molecule that interacts with the functional monomer prior to the polymerization and template removal. However, the phenomenon of a material's "memory" provided by the "footprint" of the chemical entity was first observed on silica-based materials nearly a century ago. Through the years, molecular imprinting technology has attracted the attention of many scientists. Different forms of molecularly imprinted materials, even on the nanoscale, were elaborated, predominantly using organic polymers to induce the "memory". This field has expanded quickly in recent years, providing versatile tools for the separation or detection of numerous chemical compounds or even macromolecules. In this review, we would like to emphasize the role of the molecular imprinting process in the formation of highly specific siloxane-based nanomaterials. The distinct chemistry of siloxanes provides an opportunity for the facile functionalization of the surfaces of nanomaterials, enabling us to introduce additional properties and providing a way for vast applications such as detectors or separators. It also allows for catalyzing chemical reactions providing microreactors to facilitate organic synthesis. Finally, it determines the properties of siloxanes such as biocompatibility, which opens the way to applications in drug delivery and nanomedicine. Thus, a brief outlook on the chemistry of siloxanes prior to the discussion of the current state of the art of siloxane-based imprinted nanomaterials will be provided. Those aspects will be presented in the context of practical applications in various areas of chemistry and medicine. Finally, a brief outlook of future perspectives for the field will be pointed out.