Selectivity Of Molecularly Imprinted Polymer Research Articles

Molecularly imprinted polymer for the selective removal of direct violet 51 from wastewater: synthesis, characterization, and environmental applications

Abstract Molecularly imprinted polymers (MIPs) are a diverse class of materials designed for selective molecular recognition. These polymers are synthesized with particular binding sites that are suited to a target molecule or a collection of structurally similar molecules through the use of a process called molecular imprinting. MIPs were synthesized in this work to specifically remove direct violet 51 from occupational leachates and aqueous solutions. Methacrylic acid functioned as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2-azobisisobutyronitrile (AIBN) as the initiator, and alcohol as a porogenic solvent. To improve the dye removal effectiveness, a number of factors were optimized, including time, pH, analyte concentrations, and MIP/NIP dosages. The findings showed that MIPs had a much greater capacity for direct violet 51 adsorption than nonimprinted polymers (NIPs), with MIP adsorption capacity reaching 42.553 mg g−1 and NIP adsorption capacity reaching 7 mg g−1. The pseudo 2nd-order model described the adsorption kinetics, and the rate constant (K 2) for MIPs was found to be 0.00251 mg g−1 min. Furthermore, a high rebinding efficiency of 94 % was observed when the selectivity of MIPs for direct violet 51 was assessed against structurally similar templates.

Design and controlled synthesis of molecularly imprinted fluorescence sensor supported by multifunctional magnetic covalent organic framework: Efficient detection of clofibric acid in the environment

While some studies have explored magnetic covalent organic frameworks (MCOFs) for fluorescence sensing, substantial research gaps remain, especially in integrating molecular imprinting technology (MIT). In this study, superparamagnetic Fe3O4 cores were modified, and a monomer-mediated in situ growth strategy was used to synthesize uniform, multifunctional MCOFs nanoparticles. Subsequently, molecularly imprinted polymers (MIPs) were synthesized via a sol-gel method and deposited on MCOFs, forming MCOFs-supported molecularly imprinted fluorescent sensors (MCOFs@MIPs) for trace analysis of clofibric acid (CLF). This was the first application of molecularly imprinted fluorescence sensing technology for detecting CLF. MCOFs@MIPs combined the superparamagnetism of Fe3O4, the stability and signal amplification of COFs, and the selectivity of MIPs for CLF. Studies demonstrated that MCOFs@MIPs had a maximum fluorescence response in isopropanol, with an optimal dosage of 0.39 mg/mL, an imprinting factor (IF) of 2.73, a detection limit of 94 nM, and a range of 0 ∼ 300 µM. Characterizations revealed that the fluorescence quenching of MCOFs@MIPs was based on a photoinduced electron transfer (PET) mechanism, with MCOFs@MIPs as donors and CLF as acceptors. MCOFs@MIPs were used to detect CLF in actual samples from food, water, agricultural products, cosmetics, and human metabolites. The detection results were consistent with those from high-performance liquid chromatography (HPLC). Additionally, the recoveries of MCOFs@MIPs for actual samples ranged from 94.4 % to 100.7 %, demonstrating exceptional reliability, reusability, and accuracy.

Developments and Applications of Molecularly Imprinted Polymer-Based In-Tube Solid Phase Microextraction Technique for Efficient Sample Preparation.

Despite advancements in the sensitivity and performance of analytical instruments, sample preparation remains a bottleneck in the analytical process. Currently, solid-phase extraction is more widely used than traditional organic solvent extraction due to its ease of use and lower solvent requirements. Moreover, various microextraction techniques such as micro solid-phase extraction, dispersive micro solid-phase extraction, solid-phase microextraction, stir bar sorptive extraction, liquid-phase microextraction, and magnetic bead extraction have been developed to minimize sample size, reduce solvent usage, and enable automation. Among these, in-tube solid-phase microextraction (IT-SPME) using capillaries as extraction devices has gained attention as an advanced "green extraction technique" that combines miniaturization, on-line automation, and reduced solvent consumption. Capillary tubes in IT-SPME are categorized into configurations: inner-wall-coated, particle-packed, fiber-packed, and rod monolith, operating either in a draw/eject system or a flow-through system. Additionally, the developments of novel adsorbents such as monoliths, ionic liquids, restricted-access materials, molecularly imprinted polymers (MIPs), graphene, carbon nanotubes, inorganic nanoparticles, and organometallic frameworks have improved extraction efficiency and selectivity. MIPs, in particular, are stable, custom-made polymers with molecular recognition capabilities formed during synthesis, making them exceptional "smart adsorbents" for selective sample preparation. The MIP fabrication process involves three main stages: pre-arrangement for recognition capability, polymerization, and template removal. After forming the template-monomer complex, polymerization creates a polymer network where the template molecules are anchored, and the final step involves removing the template to produce an MIP with cavities complementary to the template molecules. This review is the first paper to focus on advanced MIP-based IT-SPME, which integrates the selectivity of MIPs into efficient IT-SPME, and summarizes its recent developments and applications.

Enhancing Selectivity with Molecularly Imprinted Polymers via Non-Thermal Dielectric Barrier Discharge Plasma.

Molecularly imprinted polymers (MIPs) are synthetic polymers that mimic the functions of antibodies. Though MIPs are promising tools in various areas, achieving high selectivity in MIPs can be difficult. To improve selectivity, various approaches have been implemented; however, the role of polymerization methods or synthetic techniques in enhancing the selectivity of MIPs has not been studied and remains a crucial area for further research. MIPs are typically prepared from free radical reactions. Recently, we found that Dielectric Barrier Discharge (DBD) plasma can be used to initiate the polymerization of vinyl monomers. The DBD plasma method allows the monomers to associate with the template molecules and initiate polymerization with minimal disruption to the positioning of the monomers. We hypothesize that this could be a preferred method to prepare MIPs over the traditional radical reaction that may cause a disturbance of the pre-associated monomers on the templates for the polymerization. Chicken egg white serum albumin (CESA) was used as the template protein for the MIPs. Our results show that in all test conditions, approximately twofold improvement in selectivity was achieved, which is the primary performance metric for MIPs. This enhancement was evident across all categories, including MIPs prepared from various monomer combinations.

Rational Design of Non-Covalent Imprinted Polymers Based on the Combination of Molecular Dynamics Simulation and Quantum Mechanics Calculations.

Molecular imprinting is a promising approach for developing polymeric materials as artificial receptors. However, only a few types of molecularly imprinted polymers (MIPs) are commercially available, and most research on MIPS is still in the experimental phase. The significant limitation has been a challenge for screening imprinting systems, particularly for weak functional target molecules. Herein, a combined method of quantum mechanics (QM) computations and molecular dynamics (MD) simulations was employed to screen an appropriate 2,4-dichlorophenoxyacetic acid (2,4-D) imprinting system. QM calculations were performed using the Gaussian 09 software. MD simulations were conducted using the Gromacs2018.8 software suite. The QM computation results were consistent with those of the MD simulations. In the MD simulations, a realistic model of the 'actual' pre-polymerisation mixture was obtained by introducing numerous components in the simulations to thoroughly investigate all non-covalent interactions during imprinting. This study systematically examined MIP systems using computer simulations and established a theoretical prediction model for the affinity and selectivity of MIPs. The combined method of QM computations and MD simulations provides a robust foundation for the rational design of MIPs.

Development of antibody-engineered molecularly imprinted polymers for selective capture of aflatoxin B1 from starchy food and medicinal materials

Molecularly imprinted polymers(MIPs) have been widely used as selective recognition materials for analysis and detection of mycotoxins, such as aflatoxin B1(AFB1). However, little attention was given to investigate key factors that affecting selectivity and specificity of MIPs, such as functional monomers and imprinted cavity compatibility. Inspired by the recognition of antibody to antigen, we designed and employed amino acids as functional monomers with multiple interaction sites via hydrogen bonding and aromatic π-π stacking, meanwhile, synthesized structurally matched alternative template, 5,7-dimethoxycyclopentenone [2,3-c]coumarin(DMPC) to prepare MIPs via silica surface grafting. The adsorption of antibody-engineered MIPs was enhanced significantly compared to that of MIPs prepared by conventional functional monomers and dummy templates for selective capture of AFB1. And the specific recognition sites of MIPs left by DMPC conferred the most remarkable selectivity toward AFB1 among aflatoxins. The mechanism and contribution of functional groups and imprinted cavities for selective adsorption of AFB1 were elucidated, providing a different approach to improving functional monomers and templates in MIPs. The solid phase extraction cartridges packed DMPC-ATry-MIPs@SiO2 were used for enrichment of AFB1 in Lotus seeds and Coix seeds. The recoveries were 94.48–112.90 % and 83.32–116.04 % respectively, even after being used five times repeatedly. The cartridges could replace expensive and low-reusability immunoaffinity columns in the analysis and detection of AFB1 in real samples, providing a kind of promising sample pretreatment materials for trace analysis in food and drugs.

Innovative approaches to suppress non-specific adsorption in molecularly imprinted polymers for sensing applications

Molecularly imprinted polymers (MIPs) are synthetic antibodies developed to bind selectively with specific molecules. They function through a particular recognition process involving their cavities and functional groups. Nevertheless, functional groups located outside these cavities are the main cause of non-specific molecule binding, thus reducing the effectiveness of MIPs in sensing applications. This work focused on enhancing the selectivity and performance of MIPs through electrostatic modification with surfactants. The study investigates the use of two surfactants, namely sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB), to eliminate non-specific adsorption in MIPs. The binding isotherms of the target molecule sulfamethoxazole (SMX) on MIPs and non-imprinted polymers (NIPs) were analyzed, showing higher adsorption capacity of MIPs due to the specific cavities. The modification with SDS or CTAB effectively eliminated non-specific adsorption in MIPs. The kinetic adsorption behavior further demonstrated the efficacy of MIP+--SDS/CTAB in the selective adsorption of SMX. Calibration curves showcase the methodology's analytical capabilities, achieving low limit of detection for SMX 6 ng mL−1 using MIP +-SDS. The stability study confirmed that the developed MIP +/--SDS/CTAB remains stable even at high temperatures, demonstrating its suitability for on-site applications. The methodology was successfully applied to detect SMX in milk and water samples, achieving promising recoveries. Overall, the electrostatic modification of MIPs with surfactants emerges as a valuable strategy for enhancing selectivity and performance in target molecule recognition and detection.

A MOF-doped molecularly imprinted polymer/MOF hybrid gel incorporating with pH-buffering sodium acrylate for practical detoxification of organophosphorus nerve agents

The fatal toxicity of organophosphorus nerve agents (ONAs) and the realistic condition of chemical attack occurring place trigger the urgent need to develop catalyst materials with degrading ability under the natural environment without bulk water and bases. Here, we strategically design a molecularly imprinted polymer (MIP)/MOF hybrid catalyst material by integrating enzyme-mimic MIP with Zr-MOF UiO-66-NH2 which demonstrate promising catalytic performance for degradation of ONAs. Furthermore, sodium acrylate functions as a hydrophilic and alkaline functional unit together with pyridine-amidoxime based functional monomers (PAAO) to copolymerize into molecularly imprinted polymeric network. The basic sodium carboxylate groups were installed near the active sites to provide appropriate alkaline microenvironment, non-bulk water and acid buffer capacity for the catalysis in pure water. The resultant MIP/MOF composite catalyst demonstrate outstanding catalytic activities in both liquid and solid phase hydrolysis of ONAs. Specifically, the half-life of liquid phase hydrolysis catalyzed by MIP/UiO-66-NH2-0.5 achieves 9.4 min for diethyl-4-nitrophenyl phosphate (DENP) and 10 min for dimethyl 4-nitrophenyl phosphate (DMNP), and solid-state hydrolysis present rapid degradation efficiency with a half-life of 28.6 min. In addition, composite catalyst MIP-Ag/UiO-66-NH2-0.5 that retains substrate selectivity of MIP, enables the simultaneous degradation of two types of organophosphorus substrates (phosphate and thiophosphate) by MIP and MOF in a synergistic way. Summarily, this work displays promising potential of MIP/MOF hybrid enzyme-like catalyst as effective and practical material for the practical protection and detoxification of organophosphorus nerve agents.

Functionalized Cochlear Implant Electrode for Intracochlear Histamine Detection via Molecularly Imprinted Polymer Coating

By coating the electrodes of a cochlear implant (CI) electrode array with a powdered form of molecularly imprinted polymer (MIP), a straightforward process to functionalize existing electrodes to selectively detect histamine is demonstrated. Detection is based on non‐Faradaic impedance spectroscopy, omitting the need for a reference electrode or redox mediators, and fitting to a 5‐element equivalent electronic circuit. Proof‐of‐concept measurements on three functionalized cochlear implants in three human cadaveric cochleae indicate a level of detection of 200 nM of histamine in albumin‐based artificial perilymph following a sigmoid dose‐response trend up to 10 mM. This sensitivity enables quantized and localized analysis of histamine‐mediated inflammation immediately following the CI operation. The selectivity and adaptability of MIPs opens possibilities to detect a wide spectrum of inflammation markers inside the human cochlea and could be used for fast mid‐ or postoperative intervention to improve the medical implant's outcome.

A novel carbonized polymer dots-based molecularly imprinted polymer with superior affinity and selectivity for oxytetracycline removal

Molecularly imprinted polymers (MIPs) synthesized from chain functional monomers are restricted by spatial extension and exhibit relatively poor affinity and selectivity; this results in unsatisfactory applications in complex media. In this study, we prepared unique spherical carbonized polymer dots (CPDs-OH) via the incomplete carbonization of 1-allyl-3-vinylimidazolium bromide and ethylene glycol, and used it as a functional monomer to prepare a newly imprinted polymer (CPDs-OH@MIP) in aqueous media. As a result, the CPDs-OH@MIP exhibited effective recognition of oxytetracycline with an impressive imprinting factor of 6.17, surpassing MIPs prepared with chain functional monomers (1–3). Furthermore, CPDs-OH@MIP exhibited excellent adsorption for oxytetracycline (278.52 mg g−1) and achieved equilibrium in 30 min, with stronger resistance to coexisting cations, anions, and humic acid. Compared to other MIPs and adsorbents, the recognition performance of CPDs-OH@MIP improved 2–4 times; this polymer could remove >92.1% of oxytetracycline in real water samples with at least 10 cycle times. CPDs-OH@MIP prepared using the special spherical monomer forms a denser structure with fewer nonimprinted regions and precisely imprinted sites, remarkably improving the affinity and selectivity of MIPs combined via hydrogen bonds and electrostatic and π-π interactions. Our proposed strategy provides an effective basis for breakthroughs in the practical application of MIPs.

Molecularly imprinted photoelectrochemical sensing platform based on g-C3N4/MOFs photoresponsive oxidase mimic for norfloxacin detection

A molecularly imprinted photoelectrochemical sensor was successfully designed for sensitive detection of norfloxacin (NOR) based on poly (o-phenylenediamine) (PoPD) sensitized g-C3N4/Zr-MOFs(Fe) composite. Herein g-C3N4/Zr-MOFs(Fe) heterojunction composite was explored as photoresponsive oxidase mimic and photoactive material for the purpose of enhancing photoelectrochemical performances. In addition, PoPD molecularly imprinted polymers (MIPs) were introduced not only to act as the recognition element for selective performance, but also to possess photosensitive effect, which enhanced the photocurrent of sensor. SEM, element mapping method, XRD, UV–Vis and electrochemical impedance spectroscopy were employed for the characterization of the structural, chemical composition, optical and electrical properties of g-C3N4/Zr-MOFs(Fe) composite. Thanks to the photoresponsive oxidase mimic property and the selectivity of MIPs, the as-prepared sensor presented a good linear range of from 1.0 × 10−8 mol/L to 2.0 × 10−6 mol/L with NOR and a limit of detection of 5.7 × 10−9 mol/L. Moreover, the sensor platform has been proved to have excellent selectivity and real sample application.

Assessment of Molecularly Imprinted Polymers as Selective Solid-Phase Extraction Sorbents for the Detection of Cloxacillin in Drinking and River Water.

This paper describes a new methodology for carrying out quantitative extraction of cloxacillin from drinking and river water samples using a molecularly imprinted polymer (MIP) as a selective sorbent for solid-phase extraction (MISPE). Several polymers were synthesized via thermal polymerization using cloxacillin as a template, methacrylic acid (MAA) as a functional monomer, ethyleneglycoldimethacrylate (EGDMA) as a cross-linker and different solvents as porogens. Binding characteristics of the adequate molecularly imprinted and non-imprinted (NIP) polymers were evaluated via batch adsorption assays following the Langmuir and Freundlich isotherms and Scatchard assays. The parameters related to the extraction approach were studied to select the most appropriate polymer for cloxacillin determination. Using the optimized MIP as the SPE sorbent, a simple sample treatment methodology was combined with high-performance liquid chromatography (HPLC) to analyze cloxacillin residues in drinking and river water. Under the optimum experimental conditions, the MISPE methodology was validated using spiked samples. The linearity for cloxacillin was assessed within the limits of 0.05-1.5 µg L-1 and the recovery percentage was higher than 98% (RSD < 4%). The limits of detection and limits of quantification were 0.29 and 0.37 µg L-1 and 0.8 and 0.98 µg L-1 for drinking and river water, respectively. The selectivity of MIP against other ß-lactam antibiotics with similar structures (oxacillin, cefazoline, amoxicillin and penicillin V) was studied, obtaining a good recovery higher than 85% for all except cefazoline. The proposed MISPE-HPLC methodology was successfully applied for the detection of cloxacillin in drinking water from Canal de Isabel II (Madrid) and river water from the Manzanares River (Madrid).

Fabrication and application of molecularly imprinted polymer doped carbon dots coated silica stationary phase

Facing the difficulties in chromatographic separation of polar compounds, this investigation devotes to developing novel stationary phase. Molecularly imprinted polymers (MIPs) have aroused wide attention, owing to their outstanding selectivity, high stability, and low cost. In this work, a novel stationary phase based on carbon dots (CDs), MIP layer, and silica beads was synthesized to exploit high selectivity of MIPs, excellent physicochemical property of CDs, and outstanding chromatographic performances of silica microspheres simultaneously. The MIP doped CDs coated silica (MIP-CDs/SiO2) stationary phase was systematically characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurement, and carbon elemental analysis. Furthermore, the chromatographic performance of the MIP-CDs/SiO2 column was thoroughly assessed by using a wide variety of compounds (including nucleosides, sulfonamides, benzoic acids, and some other antibiotics). Meanwhile, the separation efficiency of the MIP-CDs/SiO2 stationary phase was superior to other kinds of stationary phases (e.g. nonimprinted NIP-CDs/SiO2, MIP/SiO2, and C18–SiO2). The results demonstrated that MIP-CDs/SiO2 column exhibited best performance in terms of chromatographic separation. For all tested compounds, the resolution value was not less than 1.60, and the column efficiency of MIP-CDs/SiO2 for thymidine was 22,740 plates/m. The results further indicate that the MIP-CDs/SiO2 column can combine the good properties of MIP, CDs, with those of silica microbeads. Therefore, the developed MIP-CDs/SiO2 stationary phase can be applied in the separation science and chromatography-based techniques.

Molecularly imprinted polymers-isolated AuNP-enhanced CdTe QD fluorescence sensor for selective and sensitive oxytetracycline detection in real water samples

A molecularly imprinted polymers (MIPs)-isolated AuNP-enhanced fluorescence sensor, AuNP@MIPs-CdTe QDs, was developed for highly sensitive and selective detection of oxytetracycline (OTC) in aqueous medium. The developed sensor combined the advantages of strong fluorescence signal of metal-enhanced fluorescence (MEF), high selectivity of MIPs, and stability of CdTe QDs. The MIPs shell with specific recognition served as an isolation layer to adjust the distance between AuNP and CdTe QDs to optimize the MEF system. The sensor demonstrated the detection limit as low as 5.22 nM (2.40 μg/L) for a concentration range of 0.1–3.0 μM OTC and good recovery rates of 96.0–103.0% in real water samples. In addition, high specificity recognition for OTC over its analogs was achieved with an imprinting factor of 6.10. Molecular dynamics (MD) simulation was utilized to simulate the polymerization process of MIPs and revealed H-bond formation as the mainly binding sites of APTES and OTC, and finite-difference time-domain (FDTD) analysis was employed to obtain the distribution of electromagnetic field (EM) for AuNP@MIPs-CdTe QDs. The experimental results combined with theoretical analyses not only provided a novel MIP-isolated MEF sensor with excellent detection performance for OTC but also established a theoretical basis for the development of a new generation of sensors.

Molecularly imprinted polymer preparations for selective detection of C‐reactive protein: Thermodynamic and kinetic studies

AbstractC‐reactive protein (CRP) is a member of the pentraxin protein group. CRP is considered an acute‐phase protein produced by the liver during inflammation in various diseases limited to pathogenic infections. It is very important that serum CRP concentration can be measured quickly, reliably and easily. Therefore, a three‐dimensional crosslinked molecularly imprinted polymer (MIP) with selective recognition sites for CRP was synthesized (CRP‐MIP) and characterization analyzes (scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis) were performed. The binding abilities of the synthesized polymers by adsorption of CRP in aqueous solution were evaluated in detail and compared with the abilities of an unprinted polymer (CRP‐NIP) used as a reference. It was found that the MIP prepared by the printing effect selectively adsorbed the template molecule CRP. For this effect, the selectivity of MIP toward CRP and various positive acute‐phase reactants such as α1‐antitrypsin and α1‐acid glycoprotein was evaluated and high selectivity toward CRP was obtained. CRP‐MIP was used to remove CRP from crude human serum, and the recovery was up to 91%. Adsorption process of CRP from aqueous solutions on polymeric adsorbents; equilibrium was evaluated in terms of kinetic and thermodynamic conditions and the necessary parameters to describe the process were calculated under these conditions. Adsorption data: the pseudo‐first order kinetic model, the pseudo‐second order kinetic model, the Elovich kinetic model and the intraparticle diffusion model were studied and the thermodynamic parameters ΔG°, ΔH°, and ΔS° were calculated.

Molecularly Imprinted Solid Phase Extraction Strategy for Quinic Acid.

Quinic acid (QA) and its ester conjugates have been subjected to in-depth scientific investigations for their antioxidant properties. In this study, molecularly imprinted polymers (MIPs) were used for selective extraction of quinic acid (QA) from coffee bean extract. Computational modelling was performed to optimize the process of MIP preparation. Three different functional monomers (allylamine, methacrylic acid (MAA) and 4-vinylpyridine (4-VP)) were tested for imprinting. The ratio of each monomer to template chosen was based on the optimum ratio obtained from computational studies. Equilibrium rebinding studies were conducted and MIP C, which was prepared using 4-VP as functional monomer with template to monomer ratio of 1:5, showed better binding performance than the other prepared MIPs. Accordingly, MIP C was chosen to be applied for selective separation of QA using solid-phase extraction. The selectivity of MIP C towards QA was tested versus its analogues found in coffee (caffeic acid and chlorogenic acid). Molecularly imprinted solid-phase extraction (MISPE) using MIP C as sorbent was then applied for selective extraction of QA from aqueous coffee extract. The applied MISPE was able to retrieve 81.918 ± 3.027% of QA with a significant reduction in the amount of other components in the extract.

Preparation of arctiin moleculary imprinted polymers with 4-vinylpyridine and Allyl-β-cyclodextrin as binary monomers under molecular crowding conditions

This paper reported a feasible method to prepare molecularly imprinted polymer (MIPs) using 4-vinylpyridine (4-VP) and Allyl-β-cyclodextrin (β-CD) as binary functional monomer in the presence of polystyrene (PS). This is the first time that a surrounding of macromolecular crowding was established to improve the imprinting effect of cyclodextrins as monomer in organic solvents. The morphological and characteristics of the polymers with macromolecular crowding reagents were investigated by scanning electron microscope (SEM), fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and nitrogen adsorption experiments. The MIPs were synthesized with 4-VP and β-CD as binary functional monomers, a series of experiments were conducted to compare with the control groups. Furthermore, the selectivity of MIP for analogues experiment showed that the β-CD/4-VP MIP has higher specific recognition for arctiin than β-CD/4-VP NIP. A purification method by β-CD/4-VP MIPs coupled with macromolecular crowding reagents was developed for extraction arctiin from Arctium lappa L. In the MIP-SPE process, the optimal washing and eluting reagents are methanol/water (5:5) and methanol/acid (9:1), respectively. When using the β-CD/4-VP MIPs as SPE absorbent, the mean recoveries for arctiin were 87% with purity of 95%. All the results indicate that this synthetic method using 4-VP and β-CD as binary functional monomers in the presence of PS is a promising method for the preparation of selective adsorbents for arctiin analysis in Arctium lappa L.

Selective enrichment of microbiota-derived tryptophan metabolites in mouse faeces based on molecularly imprinted solid-phase extraction for HPLC analysis

Gut microbiota-derived tryptophan (TRP) metabolites, especially the indole derivatives, function as critical modulators of intestinal immune function and integrity via modulating the aryl hydrocarbon receptor pathway. Selective enrichment of these indole metabolites in biological samples is important for quantitative determination by routine methods such as HPLC. Here, we report a molecularly imprinted polymer (MIP) for solid-phase extraction (SPE) of TRP-derived indole metabolites from faeces of mice. The MIP was synthesized by surface polymerization by using indole-3-acetic acid (IAA) and acrylamide after cross-linking by ethylene glycol dimethacrylate (EGDMA) and initialed by 2′,2-azobisisobutyronitrile (AIBN). The MIPs were then characterized by transmission electron microscope (TEM) and fourier transform infrared spectroscopy (FTIR), and the adsorption capacity, selectivity and reusability of MIPs were systematically evaluated. Results showed that IAA-MIPs showed a uniformly distributed nanoshell layer with a thin shell thickness of 26 nm. The IAA-MIPs could selectively adsorb IAA, indole-3-propionic acid (IPA), and indole-3-lactic acid (ILA) in a mixed solution that also contains TRP and tyrosine. The adsorption capacity of IAA-MIPs only slightly decreased with the increase of recycling use. As purification material for SPE, the IAA-imprinted polymers (IAA-MIPs) were successfully applied to extract IAA, IPA, and ILA from normal and colitis mice for HPLC determination. Collectively, these surface molecularly imprinted polymers could find extensive use to selective enrichment of microbiota-derived indole metabolites in biological samples.

Raman Studies on Surface-Imprinted Polymers to Distinguish the Polymer Surface, Imprints, and Different Bacteria.

Molecularly imprinted polymers (MIPs) are widely used as robust biomimetic recognition layers in sensing devices targeting a wide variety of analytes including microorganisms such as bacteria. Assessment of imprinting success and selectivity toward the target is of great importance in MIP quality control. We generated Escherichia coli-imprinted poly(styrene-co-DVB) as a model system for bacteria-imprinted polymers via surface imprinting using a glass stamp with covalently immobilized E. coli. Confocal Raman Microscopy was successfully employed to visualize bacteria, imprints, and polymer and to distinguish them from each other. The method has proven highly feasible for assessing if imprinting had been successful. In addition, we developed a method for selectivity investigation of bacteria MIPs based on combining Confocal Raman Microscopy and Partial Least Squares Discriminant Analysis (PLS-DA). The Raman spectra of E. coli and Bacillus cereus were acquired on E. coli-imprinted poly(styrene-co-DVB) and used to establish a PLS-DA model for differentiating between the bacteria species. Model validation demonstrated a correct classification of 95% of Raman spectra, indicating sufficient accuracy of the model for future use in MIP selectivity studies. Simultaneous differentiation of 3 bacteria species (E. coli, B. cereus, and Lactococcus lactis) on E. coli-imprinted poly(styrene-co-DVB) proved more difficult, which might be due to the limited depth resolution of the confocal Raman microscope resulting in the presence of interfering signals from the polymer substrate. It might be possible to overcome this obstacle by selective enhancement of the Raman signals originating from bacteria surfaces, such as tip enhanced Raman spectroscopy.

Fabrication of a fluorescence probe via molecularly imprinted polymers on carbazole-based covalent organic frameworks for optosensing of ethyl carbamate in fermented alcoholic beverages

Ethyl carbamate (EC), which is a group 2A carcinogen, is a byproduct formed in the alcohol fermentation process that can accumulate with heating, transportation, and storage. In this study, molecularly imprinted polymers (MIPs) on carbazole-based covalent organic frameworks (COFs) were prepared as a fluorescence probe for the optosensing of EC in fermented alcoholic beverages. The excellent optical properties of carbazole-based COFs coupled with the good adsorption and selectivity of MIPs provided fast and efficient recognition of EC. MIPs on carbazole-based COFs exhibited advantages of high efficiency, a good separation effect, fluorescence dependence, and reproducibility. A good linear relationship was obtained over the concentration range of 1–200 μg L−1, with a low limit of detection (LOD) of 0.607 μg L−1. The RSD precision and five-cycle reproducibility were lower than 4.91% and 6.38%, respectively, and the recoveries were 85.30%–109.49%. This optosensor was applied to quantify EC contents in several fermented alcoholic beverages, all of which were less than LOD. The results of the optosensors based on MIPs on carbazole-based COFs were then validated using standard gas chromatography–mass spectrometry (GC-MS), which gave results consistent with the proposed method.