Application of molecularly-imprinted polymers in solid-phase microextraction techniques

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.

Recent Advances in Bioanalysis of Cephalosporins Toward Green Sample Preparation

This review highlights recent advances in the bioanalysis of cephalosporins using liquid chromatographic methods, focusing on green sample preparation (GSP) techniques. Cephalosporins, a class of β-lactam antibiotics, are critical in combating bacterial infections but present challenges related to drug resistance and toxicity. This article evaluates various sample preparation methods, including solid-phase extraction, solid-phase microextraction, and protein precipitation, which have been employed in the extraction and quantification of cephalosporins from biological matrices. Special attention is given to the optimization of critical parameters, such as pH, extraction solvents, and purification techniques to maximize analytes' recovery and sensitivity. Emerging trends in GSP, such as the use of molecularly imprinted polymers and miniaturized processing devices, are also discussed. The review underscores the growing importance of integrating environmentally friendly approaches in cephalosporin bioanalysis, paving the way for future innovations in bioanalytical research.

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.

Magnetic materials as adsorbents for the pre-concentration and separation of active ingredients from herbal medicine

Herbal medicine (HM) is crucial in disease management and contains complex compounds with few active pharmacological ingredients, presenting challenges in quality control of raw materials and formulations. Effective separation, identification, and analysis of active components are vital for HM efficacy. Traditional methods like liquid-liquid extraction and solid-phase extraction are time-consuming and environmentally concerning, with limitations such as sorbent issues, pressure, and clogging. Magnetic solid-phase extraction uses magnetic sorbents for targeted analyte separation and enrichment, offering rapid, pressure-free separation. However, inorganic magnetic particles' aggregation and oxidation, as well as lack of selectivity, have led to the use of various coatings and modifications to enhance specificity and selectivity for complex herbal samples. This review delves into magnetic composites in HM pretreatment, specifically focusing on encapsulated or modified magnetic nanoparticles and materials like silica, ionic liquids, graphene family derivatives, carbon nanotubes, metal-organic frameworks, covalent organic frameworks, and molecularly imprinted polymers.

Molecularly imprinted polymer-based electrochemical sensors for monitoring the persistent organic pollutants chlorophenols

Because of the serious risks they pose to the environment and public health, chlorophenols (CPs), a typical class of the most persistent organic pollutants, have drawn increasing attention. Monitoring CPs effectively has become a pressing and difficult problem. The rapidly increasing need for onsite and real-time CP detection has led to the consideration of electrochemical sensing as a workable solution. Molecularly imprinted polymer (MIP)-based electrochemical sensing has emerged as a promising area for environmental monitoring in response to this analytical problem. MIPs, in conjunction with miniature electrochemical transducers, provide the opportunity to detect target analytes in situ. These devices have the advantages of great chemical and physical stability, cheap production costs, good selectivity, and quick response times. Most studies suggest that these sensors use nanoparticles to improve their analytical properties, especially sensitivity. Furthermore, these sensors have successfully used real water samples without the need for time-consuming pretreatment procedures. This article provides an overview of electrochemical MIP-based sensors reported to detect CPs in water samples. To obtain the highest sensitivity, special consideration is given to the fabrication of the sensors, which includes the use of various functional monomers, sensing platforms, and materials. Several other parameters are also discussed, including the linear concentration range, limit of detection, and the types of water samples that were examined.

Passive sweat wearable: A new paradigm in the wearable landscape toward enabling "detect to treat" opportunities

Growing interest over recent years in personalized health monitoring coupled with the skyrocketing popularity of wearable smart devices has led to the increased relevance of wearable sweat-based sensors for biomarker detection. From optimizing workouts to risk management of cardiovascular diseases and monitoring prediabetes, the ability of sweat sensors to continuously and noninvasively measure biomarkers in real-time has a wide range of applications. Conventional sweat sensors utilize external stimulation of sweat glands to obtain samples, however; this stimulation influences the expression profile of the biomarkers and reduces the accuracy of the detection method. To address this limitation, our laboratory pioneered the development of the passive sweat sensor subfield, which allowed for our progress in developing a sweat chemistry panel. Passive sweat sensors utilize nanoporous structures to confine and detect biomarkers in ultra-low sweat volumes. The ability of passive sweat sensors to use smaller samples than conventional sensors enable users with sedentary lifestyles who perspire less to benefit from sweat sensor technology not previously afforded to them. Herein, the mechanisms and strategies of current sweat sensors are summarized with an emphasis on the emerging subfield of passive sweat-based diagnostics. Prospects for this technology include discovering new biomarkers expressed in sweat and expanding the list of relevant detectable biomarkers. Moreover, the accuracy of biomarker detection can be enhanced with machine learning using prediction algorithms trained on clinical data. Applying this machine learning in conjunction with multiplex biomarker detection will allow for a more holistic approach to trend predictions. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing.

Wearable and Implantable Cortisol-Sensing Electronics for Stress Monitoring

Cortisol is a steroid hormone that is released from the body in response to stress. Although a moderate level of cortisol secretion can help the body maintain homeostasis, excessive secretion can cause various diseases, such as depression and anxiety. Conventional methods for cortisol measurement undergo procedures that limit continuous monitoring, typically collecting samples of bodily fluids, followed by separate analysis in a laboratory setting that takes several hours. Thus, recent studies demonstrate wearable, miniaturized sensors integrated with electronic modules that enable wireless real-time analysis. Here, the primary focus is on wearable and implantable electronic devices that continuously measure cortisol concentration. Diverse types of cortisol-sensing techniques, such as antibody-, DNA-aptamer-, and molecularly imprinted polymer-based sensors, as well as wearable and implantable devices that aim to continuously monitor cortisol in a minimally invasive fashion are discussed. In addition to the cortisol monitors that directly measure stress levels, other schemes that indirectly measure stress, such as electrophysiological signals and sweat are also summarized. Finally, the challenges and future directions in stress monitoring and management electronics are reviewed.

Non-steroidal anti-inflammatory drugs (NSAIDs) in the environment: Updates on pretreatment and determination methods

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in human and animal health care to reduce persistent inflammation, pain and fever because of their anti-inflammatory, analgesic and antipyretic effects. However, the improper discharge and disposal make it becomes a major contaminant in the environment, which poses a big threat to the ecosystem. For this reason, accurate, sensitive, effective, green, and economic techniques are urgently required and have been rapidly developed in recent years. This review summarizes the advancement of sample preparation technologies for NSAIDs involving solid-phase extraction, solid-phase microextraction, liquid-phase microextraction, QuEChERS, and matrix solid-phase dispersion. Meanwhile, we overview and compare analytical technologies for NSAIDs, including liquid chromatography-based methods, gas chromatography-based methods, capillary electrophoresis, and sensors, particularly the development of liquid chromatography-based methods. Furthermore, we focus on their progress and conduct a comparison between their advantages and disadvantages.

Sweeteners in food samples: An update on pretreatment and analysis techniques since 2015

Sweeteners play an irreplaceable role in daily life and have been found in multitudinous food products. However, excessive or unreasonable intake of sweeteners as food additives brings about untoward problems due to the accumulation in the human body. Therefore, a comprehensive review of different sweeteners' pretreatment and determination methods is urgently needed. In this review, we comprehensively reviewed the progress of different pretreatment and detection methods for sweeteners in various food, focusing on the latest development since 2015. Current state-of-the-art technologies, such as headspace single-drop microextraction, ultrasound-assisted emulsification microextraction, solid-phase microextraction, two-dimensional liquid chromatography, and high-resolution mass spectrometry, are thoroughly discussed. The advantages, disadvantages, critical comments, and future perspectives are also proposed. This review is expected to provide rewarding insights into the future development and broad application of pretreatment and detection methods for sweeteners in different food samples.

Selective fluorescent probe for sensitive determination of bisphenol A based on molecularly imprinted polymers decorated carbon dots derived from citric acid and ethylenediamine

Bisphenol A (BPA) is an endocrine disrupting chemical and poses a grave threat to the human health. Herein, a fluorescent probe constructed with molecularly imprinted polymers decorated carbon dots (CDs@MIPs) was proposed for determination of BPA with high selectivity. The CDs@MIPs were constructed using BPA, 4-vinylpyridine and ethylene glycol dimethacrylate as template, functional monomer and cross linker, respectively. The obtained fluorescent probe not only owned a highly selective recognition function derived from MIPs but also displayed an excellent sensitivity for sensing BPA stemmed from CDs. The fluorescence intensity of CDs@MIPs was varied before and after the removal of BPA templates. The fluorescent decrease fraction of the fluorescent probe demonstrates a nice linearity in BPA concentration range of 10-2000 nM (r² = 0.9998) and the detection limit is as low as 1.5 nM. The fluorescent probe was triumphantly utilized to sense the level of BPA in real aqueous and plastic samples with good results. Moreover, the fluorescent probe offered a wonderful means for fast identification and sensitive detection of BPA from environmental aqueous samples.

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.

Recent molecularly imprinted polymers applications in bioanalysis

Molecular imprinted polymers (MIPs) as extraordinary compounds with unique features have presented a wide range of applications and benefits to researchers. In particular when used as a sorbent in sample preparation methods for the analysis of biological samples and complex matrices. Its application in the extraction of medicinal species has attracted much attention and a growing interest. This review focus on articles and research that deals with the application of MIPs in the analysis of components such as biomarkers, drugs, hormones, blockers and inhibitors, especially in biological matrices. The studies based on MIP applications in bioanalysis and the deployment of MIPs in high-throughput settings and optimization of extraction methods are presented. A review of more than 200 articles and research works clearly shows that the superiority of MIP techniques lies in high accuracy, reproducibility, sensitivity, speed and cost effectiveness which make them suitable for clinical usage. Furthermore, this review present MIP-based extraction techniques and MIP-biosensors which are categorized on their classes based on common properties of target components. Extraction methods, studied sample matrices, target analytes, analytical techniques and their results for each study are described. Investigations indicate satisfactory results using MIP-based bioanalysis. According to the increasing number of studies on method development over the last decade, the use of MIPs in bioanalysis is growing and will further expand the scope of MIP applications for less studied samples and analytes.

β-Cyclodextrin-Based Supramolecular Imprinted Fiber Array for Highly Selective Detection of Parabens

A novel high-throughput array analytical platform based on derived β-cyclodextrin supramolecular imprinted polymer (SMIP) fibers was constructed to achieve selective enrichment and removal of parabens. SMIP fiber arrays have abundant imprinting sites and introduce the host−guest inclusion effect of the derived β-cyclodextrin, which is beneficial to significantly improve the adsorption ability of fiber for parabens. Upon combination with HPLC, a specific and sensitive recognition method was developed with a low limit of detection (0.003−0.02 µg/L, S/N = 3) for parabens analysis in environmental water. This method has a good linearity (R > 0.9994) in the linear range of 0.01−200 µg/L. The proposed SMIP fiber array with high-throughput adsorption capacity has great potential in monitoring water pollution, which also provides a reliable reference for the analysis of more categories of pharmaceutical and personal care product pollutants.

Molecularly imprinted polymers for selective extraction/microextraction of cancer biomarkers: A review

Over recent years, great efforts have been extensively documented in top scientific journals on the development of methods for early diagnosis, treatment, and monitoring of cancers which are prevalent critical diseases with a high mortality rate among men and women. The determination of cancer biomarkers using different optimum methodologies is one of the finest options for achieving these goals with more precision, speed, and at a lower cost than traditional clinical procedures. In this regard, while focusing on specific biomarkers, molecularly imprinted technology has enabled novel diagnostic techniques for a variety of diseases. Due to the well-known advantages of molecularly imprinted polymers (MIPs), this review focuses on the current trends of MIPs-based extraction/microextraction methods, specifically targeting cancer biomarkers from various matrices. These optimized methods have demonstrated high selectivity, accuracy, sorbent reusability, extraction recovery, and low limits of detection and quantification for a variety of cancer biomarkers, which are a powerful tool to provide early diagnosis, prognosis, and treatment monitoring, with potential clinical application expected soon. This review highlights the key progress, specific modifications, and strategies used for MIP synthesis. The future perspectives for cancer biomarkers purification and determination by fabricating MIP-based techniques are also discussed.

Green Chemistry and Molecularly Imprinted Membranes

Technological progress has made chemistry assume a role of primary importance in our daily life. However, the worsening of the level of environmental pollution is increasingly leading to the realization of more eco-friendly chemical processes due to the advent of green chemistry. The challenge of green chemistry is to produce more and better while consuming and rejecting less. It represents a profitable approach to address environmental problems and the new demands of industrial competitiveness. The concept of green chemistry finds application in several material syntheses such as organic, inorganic, and coordination materials and nanomaterials. One of the different goals pursued in the field of materials science is the application of GC for producing sustainable green polymers and membranes. In this context, extremely relevant is the application of green chemistry in the production of imprinted materials by means of its combination with molecular imprinting technology. Referring to this issue, in the present review, the application of the concept of green chemistry in the production of polymeric materials is discussed. In addition, the principles of green molecular imprinting as well as their application in developing greenificated, imprinted polymers and membranes are presented. In particular, green actions (e.g., the use of harmless chemicals, natural polymers, ultrasound-assisted synthesis and extraction, supercritical CO2, etc.) characterizing the imprinting and the post-imprinting process for producing green molecularly imprinted membranes are highlighted.

Recent advances in analytical strategies and microsystems for food allergen detection

Food allergies are abnormal immune responses that typically occur within short period after exposure of certain allergenic proteins in food or food-related resources. Currently, the means to treat food allergies is not clearly understood, and the only known prevention method is avoiding the consumption of allergen-containing foods. From the viewpoint of analytical methods, the effective detection of food allergens is hindered by the effects of various treatment processes and food matrices on trace amounts of allergens. The aim of this effort is to provide the reader with a clear and concise view of new advances for the detection of food allergens. Therefore, the present review explored the development status of various biosensors for the real-time, on-site detection of food allergens with high selectivity and sensitivity. The review also described the analytical consideration for the quantification of food allergens, and global development trends and the future availability of these technologies.

Molecular imprinted polymer for tramadol: Absorption and drug release studies

Smart polymeric matrices based on 2‐vinyl pyridine (2‐VPY) and three different crosslinkers: ethylene glycol dimethacrylate (EGDMA), divinylbenzene (DVB), and trimethylolpropane trimethacrylate (TMPTMA) were prepared either by the imprinting technique of the tramadol molecule or conventionally by the free radical polymerization process. The polymers were used as sorbent materials for tramadol from its solutions. The polymers prepared by the imprinting technique demonstrated superior absorption of tramadol molecules than those prepared by the conventional method. The two sorbent materials constructed from TMPTMA, regardless of the method, achieved the highest absorption capacity compared with those prepared from EGDMA or DVB. It was found that loaded imprinted polymer released more tramadol than loaded nonimprinted polymer in all media. In the acidic medium, the protonation of the nitrogen atom in the pyridine ring ionized the chains and expanded the loaded pores leading to the rapid release over the neutral and alkaline media. Additionally, the isothermal studies of MIP3 and NIP3 were extremely fitted to Freundlich adsorption and the (D–R) isotherm, respectively, while the kinetic studies of both sorbents were fitted to the pseudo‐second‐order model.

Graphene-Based Femtogram-Level Sensitive Molecularly Imprinted Polymer of SARS-CoV-2

Rapid distribution of viral-induced diseases and weaknesses of common diagnostic platforms for accurate and sensitive identification of infected people raises an urgent demand for the design and fabrication of biosensors capable of early detection of viral biomarkers with high specificity. Accordingly, molecularly imprinted polymers (MIPs) as artificial antibodies prove to be an ideal preliminary detection platform for specific identification of target templates, with superior sensitivity and detection limit (DL). MIPs detect the target template with the "lock and key" mechanism, the same as natural monoclonal antibodies, and present ideal stability at ambient temperature, which improves their practicality for real applications. Herein, a 2D MIP platform consisting of decorated graphene oxide with the interconnected complex of polypyrrole-boronic acid is developed that can detect the trace of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen in aquatic biological samples with ultrahigh sensitivity/specificity with DL of 0.326 and 11.32 fg mL-1 using voltammetric and amperometric assays, respectively. Additionally, the developed MIP shows remarkable stability, selectivity, and accuracy toward detecting the target template, which paves the way for developing ultraspecific and prompt screening diagnostic configurations capable of detecting the antigen in 1 min or 20 s using voltammetric or amperometric techniques.

Multivariate Assessment of Procedures for Molecularly Imprinted Polymer Synthesis for Pesticides Determination in Environmental and Agricultural Samples

In the case of quantitative and qualitative analysis of pesticides in environmental and food samples, it is required to perform a sample pre-treatment process. It allows to minimalize the impact of interferences on the final results, as well as increase the recovery rate. Nowadays, apart from routinely employed sample preparation techniques such as solid-phase extraction (SPE) or solid-phase microextraction (SPME), the application of molecularly imprinted polymers (MIPs) is gaining greater popularity. It is mainly related to their physicochemical properties, sorption capacity and selectivity, thermo-mechanical resistance, as well as a wide range of polymerization techniques allowing to obtain the desired type of sorption materials, adequate to a specific type of pesticide. This paper targets to summarize the most popular and innovative strategies since 2010, associated with the MIPs synthesis and analytical procedures for pesticides determination in environmental and food samples. Application of multi-criteria decision analysis (MCDA) allows for visualization of the most beneficial analytical procedures in case of changing the priority of each step of analysis (MIPs synthesis, sample preparation process—pesticides extraction, chromatographic analysis) bearing in mind metrological and environmental issues.

[Advances in application of molecularly imprinted polymers to the detection of polar pesticide residues]

Polar pesticides can be primarily classified as fungicides, herbicides, and insecticides; their rich variety and low cost have led to their extensive utilization in agriculture. However, the overuse of polar pesticides can lead to environmental contamination, such as water or soil pollution, which can also increase the risk of pesticide exposure among human life directly, or indirectly through contact with animal and plant-derived food. There are considerable differences in the physical and chemical properties of polar pesticides, as well as their trace amounts in complex food and environmental samples, posing immense challenges to their accurate detection. As a kind of artificially prepared selective adsorbent, molecularly imprinted polymers (MIPs) possess specific recognition sites complementary to template molecules in terms of the spatial structure, size, and chemical functional groups. With many advantages such as easy preparation, low cost, as well as good chemical and mechanical stability, MIPs have been widely applied in sample pretreatment and the analysis of polar pesticide residues. MIPs are typically used as adsorption materials in solid phase extraction (SPE) methods, including magnetic solid phase extraction (MSPE), dispersed solid phase extraction (DSPE), and stir bar sorptive extraction (SBSE). To rapidly detect polar pesticide residues with high sensitivity, MIPs are also used in the preparation of fluorescent sensors and electrochemical sensors. Furthermore, MIPs can be employed as the substrate in surface-enhanced Raman spectroscopy and as the substrate for the ion source in mass spectrometry for polar pesticide residue analysis. Thus far, various molecularly imprinted materials have been reported for the efficient separation and analysis of polar pesticide residues in various complex matrices. However, there is no review that summarizes the recent advances in MIPs for the determination of polar pesticides. This review introduces imprinting strategies and polymerization methods for MIPs, and briefly summarizes some new molecular imprinting strategies and preparation technologies. The application of MIPs in recent years (particularly the last five years) to the detection of polar pesticide residues including neonicotinoids, organophosphorus, triazines, azoles, and urea is then systematically summarized. Finally, the future development direction and trends for MIPs are proposed considering existing challenges, with the aim of providing reference to guide future research on MIPs in the field of polar pesticide residue detection.

A Review on Molecularly Imprinted Polymers Preparation by Computational Simulation-Aided Methods

Molecularly imprinted polymers (MIPs) are obtained by initiating the polymerization of functional monomers surrounding a template molecule in the presence of crosslinkers and porogens. The best adsorption performance can be achieved by optimizing the polymerization conditions, but this process is time consuming and labor-intensive. Theoretical calculation based on calculation simulations and intermolecular forces is an effective method to solve this problem because it is convenient, versatile, environmentally friendly, and inexpensive. In this article, computational simulation modeling methods are introduced, and the theoretical optimization methods of various molecular simulation calculation software for preparing molecularly imprinted polymers are proposed. The progress in research on and application of molecularly imprinted polymers prepared by computational simulations and computational software in the past two decades are reviewed. Computer molecular simulation methods, including molecular mechanics, molecular dynamics and quantum mechanics, are universally applicable for the MIP-based materials. Furthermore, the new role of computational simulation in the future development of molecular imprinting technology is explored.

Selective recognition of tumor cells by molecularly imprinted polymers

Molecularly imprinted polymers, developed 50 years ago, have garnered enormous attention as receptor-like materials. Lately, molecularly imprinted polymers have been employed as a specific target tool in favor of cancer diagnosis and therapy by the selective recognition of tumor cells. Although the molecular imprinting technology has been well-innovated recently, the cell still remains the most challenging target for imprinting. In this review, we summarize the advances in the synthesis of molecularly imprinted polymers suitable for the selective recognition of tumor cells. Through a sustained effort, three strategies have been developed including peptide-imprinting, polysaccharide-imprinting, and whole-cell imprinting, which have resulted in inspiring applications in effective cancer diagnosis and therapy. The major challenges and perspectives on the further directions related to the synthesis of molecularly imprinted polymers were also outlined.

Molecularly Imprinted Polymer-Quantum Dot Materials in Optical Sensors: An Overview of Their Synthesis and Applications

In the last decades analytical methods have focused on the determination of target analytes at very low concentration levels. This has been accomplished through the use of traditional analytical methods that usually require high reagent consumption, expensive equipment and long pretreatment steps. Thus, there is a demand for simple, rapid, highly selective and user-friendly detection procedures. Quantum dots (QDs) are semiconductor fluorescent nanomaterials with unique optoelectronic properties that have shown great potential for the development of fluorescence probes. Besides, the combination of QDs with molecularly imprinted polymer (MIPs), synthetic materials with selective recognition, have been proposed as useful materials in the development of optical sensors. The resulting MIP-QDs optical sensors integrate the advantages of both techniques: the high sensitivity of QDs-based fluorescence sensors and the high selectivity of MIPs. This review gives a brief overview of the strategies for the synthesis of MIPs-QDs based optical sensors, highlighting the modifications in the synthesis procedure that improve the sensor performance. Finally, a revision of recent applications in sensing and bioimaging is presented.

Insights into the structure-performance relationships of extraction materials in sample preparation for chromatography

Sample preparation is one of the most crucial steps in analytical processes. Commonly used methods, including solid-phase extraction, dispersive solid-phase extraction, dispersive magnetic solid-phase extraction, and solid-phase microextraction, greatly depend on the extraction materials. In recent decades, a vast number of materials have been studied and used in sample preparation for chromatography. Due to the unique structural properties, extraction materials significantly improve the performance of extraction devices. Endowing extraction materials with suitable structural properties can shorten the pretreatment process and improve the extraction efficiency and selectivity. To understand the structure-performance relationships of extraction materials, this review systematically summarizes the structural properties, including the pore size, pore shape, pore volume, accessibility of active sites, specific surface area, functional groups and physicochemical properties. The mechanisms by which the structural properties influence the extraction performance are also elucidated in detail. Finally, three principles for the design and synthesis of extraction materials are summarized. This review can provide systematic guidelines for synthesizing extraction materials and preparing extraction devices.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Selective enrichment-release of trace dibutyl phthalate via molecular-imprinting based photo-controlled switching followed by high-performance liquid chromatography analysis

A novel intelligent photo-controlled molecularly imprinted polymers were synthesized, based on the magnetic core-shell structure, with 4-[(4-methacryloyloxy) phenylazo] benzenesulfonic acid as the functional monomer and ethylene glycol dimethyl acrylate as the cross-linking agent. Subsequently, a series of light-controlled enrichment-release performance showed that it only took about 30 and 10 min to reach the equilibrium photosensitive characteristic peak, respectively. The photo-controlled polymers could intelligently select target molecules, the maximum adsorption capacity for dibutyl phthalate was 3.88 mg/g. However, the adsorption capacity for its structural analogue dicyclohexyl phthalate was only 0.88 mg/g. The Freundlich and Langmuir isothermal equations were discussed for the specific enrichment process. Finally, the photo-controlled molecularly imprinted polymers were successfully applied to the selective detection of dibutyl phthalate, with the recovery rate of 95.4-98.4%. It could be used for the analysis of trace dibutyl phthalate in actual samples.

Chitosan-based molecular imprinted polymer for extraction and spectrophotometric determination of ketorolac in human plasma

A selective chitosan-based ion exchange molecular imprinted polymer (MIP) was prepared for ketorolac (KET) using the sol-gel method and glutaraldehyde as a crosslinker. The nonimprinted polymer (NIP) was prepared and used as a control, during the whole experiment. The chemical and morphological characteristics of the prepared polymers were investigated using FTIR and SEM, respectively. The prepared MIP was applied to determine the optimum operational conditions for KET extraction from dilute aqueous solutions. The adsorption step was performed at pH 5 and a contact time of 20 min, using 0.1 N HCl as an elution solvent for 30 min. The specificity of the prepared polymer was indicated by an imprinting factor of 1.45. The prepared MIP was successfully applied for selective solid phase extraction and subsequent determination of KET in spiked human plasma samples over a range of 2-20 μg/mL, with a mean % recovery of 94.62% using derivative spectroscopy.

Advancements of chiral molecularly imprinted polymers in separation and sensor fields: A review of the last decade

Since chiral recognition mechanism based on molecularly imprinted polymers immerged, it has assisted countless chemical and electrochemical analytical sample preparation techniques. It has done this by enhancing the enatioseparation abilities of these techniques. The preparation and optimization of chiral molecularly imprinted polymers (CMIPs) are two favored methods in the separation and sensor fields. This review aims to present an overview of advances in the preparation and application of CMIPs in analytical approaches in different available formats (eg. column, monolithic column, cartridge, membrane, nanomaterials, pipette tip and stir bar sorptive) over the last decade. In addition, progress in the preparation and development of CMIPs-based sensor fields have been also discussed. Finally, the main application challenges of CMIPs are also summarily explained, as well as upcoming prospects in the field.

Specific recognition of cationic paraquat in environmental water and vegetable samples by molecularly imprinted stir-bar sorptive extraction based on monohydroxylcucurbit[7]uril-paraquat inclusion complex

Molecularly imprinted stir-bar coatings were created based on a hydroxylcucurbit[7]uril-paraquat inclusion complex. The inclusion complex that contained paraquat (PQ) as a template and monohydroxylcucurbit[7]uril ((OH)Q[7]) as a monomer was preassembled mainly through cavity inclusion interaction of (OH)Q[7] to form a one-dimensional self-assembly structure. The inclusion complex was anchored chemically on the surface of a glass stir bar with hydroxy-terminated poly(dimethylsiloxane) by the sol-gel technique to obtain a molecularly imprinted polymer-coated stir bar (MIP-SB). The molecularly imprinted coating showed specific adsorption for cationic PQ in aqueous media. Other quaternary amine compounds with a similar structure that coexisted in the solution, such as ethyl-viologen, diquat, and difenzoquat, were almost not extracted by the prepared MIP-SB. The sorptive capacity of the MIP-SB for PQ was nearly four times that of the non-imprinted stir bar (NIP-SB). The recognition mechanism indicated that the selectivity and extraction capacity resulted mainly from the imprinted cavity in the polymer that was formed by a one-dimensional assembly structure consisting of the (OH)Q[7]-PQ inclusion complex. The imprinted cavity was complementary to the PQ in shape, size, and functionality. A method to determine PQ in environmental water and vegetable samples was developed by combining MIP-SB sorptive extraction with HPLC-UV. The linear range was from 100 to 10,000 ng L^-1 with a 8.2 ng L^-1 detection limit for water samples and 0.02-0.85 mg kg^-1 with a 0.005 mg kg^-1 detection limit for vegetable samples. The limit of detection for both samples was lower than the EU-established maximum residual levels and that of other previously reported methods. The average recoveries were 70.0-96.1% with a relative standard deviation ≤ 7.6%, which showed the successful application in real sample analysis. Molecularly imprinted stir-bar coatings were created based on a hydroxylcucurbit[7]uril-paraquat (PQ) inclusion complex, which showed a specific recognition toward cationic PQ. A method to determine PQ in environmental water and vegetable samples was established by combining MIP-SB sorptive extraction with HPLC-UV.

Microsphere Polymers in Molecular Imprinting: Current and Future Perspectives

Molecularly imprinted polymers (MIPs) are specific crosslinked polymers that exhibit binding sites for template molecules. MIPs have been developed in various application areas of biology and chemistry; however, MIPs have some problems, including an irregular material shape. In recent years, studies have been conducted to overcome this drawback, with the synthesis of uniform microsphere MIPs or molecularly imprinted microspheres (MIMs). The polymer microsphere is limited to a minimum size of 5 nm and a molecular weight of 10,000 Da. This review describes the methods used to produce MIMs, such as precipitation polymerisation, controlled/'Living' radical precipitation polymerisation (CRPP), Pickering emulsion polymerisation and suspension polymerisation. In addition, some green chemistry aspects and future perspectives will also be given.

A fabrication strategy for protein sensors based on an electroactive molecularly imprinted polymer: Cases of bovine serum albumin and trypsin sensing

A high-performance molecularly imprinted sensing platform inspired by natural recognition mechanisms was fabricated to detect protein by employing a linear electro-polymerizable molecularly imprinted polymer as macromonomer. This was achieved via the combination of a biosensor fabrication with a self-assembly imprinting technique without the use of chemical labels. An amphipathic electroactive copolymer was designed as macro-monomer to maintain structural integrity of the protein template via self-assembly, resulting in generation of a 3D construction around the protein molecule to form imprinted sites. Electro-polymerization was utilized not only to anchor imprinted sites but also to enhance electron transfer. The adaptable sensing platform was based on a strengthened recognition reaction between the MIP layer and template protein after the generation of an electroactive network. Bovine serum albumin (BSA) and trypsin were used as model proteins to investigate the method's generality, which gave broad detection ranges of 10^-14-10^-5 mg mL^-1 for BSA and 10^-13-10^-8 mg mL^-1 for trypsin. These results indicate that the proposed fabrication offers an effective and versatile strategy for protein recognition.