Metal–Ligand Interactions in Molecular Imprinting

Molecular imprinting enables the design of highly crosslinked polymeric materials that are able to mimic natural recognition processes. Molecularly imprinted polymers exhibit binding sites with tailored selectivity toward target structures ranging from inorganic ions to biomacromolecules and even viruses or living cells. The choice of the appropriate functional monomer, crosslinker, and the nature and specificity of template–monomer interactions are critical for a successful imprinting process. The use of a metal ion mediating the interaction between the monomer and template (acting as ligands) has proven to offer a higher fidelity of imprint, which modulates the molecularly imprinted polymers (MIPs) selectivity or to endow additional features to the polymer, such as stimuli-responsiveness, catalytic activity, etc. Furthermore, limitations in using nonpolar and aprotic solvents are overcome, allowing the use of more polar solvents and even aqueous solutions as imprinting media, opening new prospects toward the imprinting of biomacromolecules (proteins, DNA, RNA, antibodies, biological receptors, etc.). This chapter aims to outline the beneficial pairing of metal ions as coordination centers and various functional ligands in the molecular imprinting process, as well as to provide an up to date overview of the various applications in chemical sensing, separation processes (stationary phases and selective sorbents), drug delivery, and catalysis

Capillary Electromigration Techniques for the Quantitative Analysis of Colchicine

The separation and UV absorbance detection of colchicine by three different capillary electrophoretic methods is described. Colchicine is known as a neutral compound, being able to be determined by electrokinetic chromatography. For the first time, a non-aqueous capillary electrophoretic method is described, based on the electromigration of ionized colchicine induced by 10 mM HClO4 in a mixture of methanol:acetonitrile (1 :2, v/v) containing 60 mM ammonium formiate, opening up new perspectives in the trace analysis of the highly toxic drug from clinical and food samples using online coupling of the CE system to a mass spectrometer. For the quantitative assessment of colchicine content from meadow saffron (Colchicum autumnale L.) seeds and 1 mg colchicine tablets, a simple, quick and sensitive micellar electrokinetic chromatographic method was developed and fully validated according to ICH guidelines in terms of selectivity, linearity, accuracy, intermediate precision and limits of detection and quantification (95.2 ng mL–1). In order to further improve the detection limits, allowing the analysis of trace levels of colchicine in biosamples and food products, an on-column preconcentration using sweeping-MEKC was investigated. Linearity of response was observed on 10–160 ng mL–1 colchicine, with an estimated detection limit of around 3 ng mL–1 colchicine. By further improving the affinity of the separation vector towards colchicine this limit could be further decreased. Preliminary application of the method for the detection of trace amounts of colchicine spiked in non-fat milk and human urine (10 ng mL–1) shows encouraging results. (doi: 10.5562/cca1765

New Materials for the Construction of Electrochemical Biosensors

The development of electrochemical sensors has attracted great interest due to these sensors’ high sensitivity and selectivity. Here, we present the general concept and the classification of biosensors, their advantages and drawbacks, the main strategies in electrochemical biosensor technology and the materials used in electrochemical sensors, such as electrodes and supporting substrates, materials for improved sensitivity and selectivity, materials for bioreceptor immobilization, and biological recognition elements. Various nanomaterials, such as carbon-based materials (carbon nanotubes, graphene, carbon nanoparticles), inorganic and organic nanoparticles (magnetic and metal nanoparticles, nanosized clays), conductive and insulating polymers (nanosized and nanostructured polymers, molecularly imprinted polymers), and hybrid materials, etc., have been successfully applied for the enhancement of the electroanalytical performance of biosensors and for the immobilization of biorecognition elements. Among these, due to their unique physiochemical features, carbon-based materials, such as carbon nanotubes and graphenes, have received special attention in recent years, and examples of surface functionalization using various types of nanoparticles are presented. The future trends in sensor research activities and areas of development that are expected to have an impact in biosensor performance, like immobilization techniques, nanotechnology, miniaturization and multisensor array determinations, are also examined

Unlocking new avenues: solid-state synthesis of molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are established artificial molecular recognition platforms with tailored selectivity towards a target molecule, whose synthesis and functionality are highly influenced by the nature of the solvent employed in their synthesis. Steps towards the "greenification" of molecular imprinting technology (MIT) have already been initiated by the elaboration of green MIT principles; developing MIPs in a solvent-free environment may not only offer an eco-friendly alternative but could also significantly influence the affinity and expected selectivity of the resulting binding sites. In the current study, the first solvent-free mechanochemical synthesis of MIPs via liquid-assisted grinding (LAG) is reported. The successful synthesis of the imprinted polymer was functionally demonstrated by measuring its template rebinding capacity and the selectivity of the molecular recognition process in comparison with the ones obtained by the conventional, non-covalent molecular imprinting process in liquid media. The results demonstrated similar binding capacities towards the template molecule and superior chemoselectivity compared to the solution-based MIP synthesis method. The adoption of green chemistry principles with all their inherent advantages in the synthesis of MIPs may not only be able to alleviate the potential environmental and health concerns associated with their analytical (e.g., selective adsorbents) and biomedical (e.g., drug carriers or reservoirs) applications but might also offer a conceptual change in molecular imprinting technology.info:eu-repo/semantics/publishedVersio

EC-SERS detection of thiabendazole in apple juice using activated screen-printed electrodes

Thiabendazole (TBZ), a benzimidazole fungicide used for post-harvest treatment, may be a trace contaminant of food matrices. In this work, we report the first EC-SERS (electrochemical-surface enhanced Raman spectroscopy) detection of TBZ in spiked apple juice using electrochemically (EC) roughened, gold-based screen-printed electrodes (AuSPEs) and portable instrumentation. Polarizing the substrate (−0.8 V vs Ag/AgCl) improves the recorded SERS signal of TBZ, allowing to reach a limit of detection (LOD) in juice of 0.061 ppm with a relatively wide linear range (0.5–10 μM) and good intermediate precision (%RSD < 10). The recovery of TBZ from unprocessed juice was found to be more than 82 %. Furthermore, a proof-of-concept integration of AuSPEs with a miniaturized flow cell for the preconcentration of TBZ and the controlled delivery of sample and reagents has been demonstrated. This approach paves the way for integrated, portable analytical systems applicable for on-site sample collection, processing, and analysis.publishedVersio

Study of nucleic acid-ligand interactions by capillary electrophoretic techniques: A review.

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Chemometrical tools for experimental design were used to study ways of improvement of cadmium (II

Toward microfluidic SERS and EC-SERS applications via tunable gold films over nanospheres

Many promising applications of surface-enhanced Raman scattering (SERS), such as microfluidic SERS and electrochemical (EC)-SERS, require immersion of plasmonic nanostructured films in aqueous media. Correlational investigations of the optical response and SERS efficiency of solid SERS substrates immersed in water are absent in the literature. This work presents an approach for tuning the efficiency of gold films over nanospheres (AuFoN) as SERS substrates for applications in aqueous environment. AuFoN are fabricated by convective self-assembly of colloidal polystyrene nanospheres of various diameters (300–800 nm), followed by magnetron sputtering of gold films. The optical reflectance of the AuFoN and Finite-Difference Time-Domain simulations in both water and air reveal the dependence of the surface plasmon band on nanospheres’ diameter and environment. SERS enhancement of a common Raman reporter on AuFoN immersed in water is analyzed under 785 nm laser excitation, but also using the 633 nm line for the films in air. The provided correlations between the SERS efficiency and optical response in both air and water indicate the best structural parameters for high SERS efficiency and highlight a route for predicting and optimizing the SERS response of AuFoN in water based on the behavior in air, which is more practical. Finally, the AuFoN are successfully tested as electrodes for EC-SERS detection of the thiabendazole pesticide and as SERS substrates integrated in a flow-through microchannel format. The obtained results represent an important step toward the development of microfluidic EC-SERS devices for sensing applications.publishedVersio

Solid-State Characterization and Solubility

The authors acknowledge Fundac\u0327a\u0303o para a Cie\u0302ncia e a Tecnologia, and FEDER, Portugal 2020, and Lisboa 2020 for funding (project LISBOA-01-0145-FEDER-030988). Financial support is also acknowledged from grant POWR.03.02.00-00-I026/16 co-financed by the European Union through the European Social Fund under the Operational Program Knowledge Education Development and from Adam Mickiewicz University for the funds from the Initiative of Excellence Research University (ID-UB) program.This work is a contribution to the COST Action CA18112-Mechanochemistry for Sustainable Industry. Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.New cocrystals of praziquantel with suberic, 3-hydroxybenzoic, benzene-1,2,4,5-tetracarboxylic, trimesic, and 5-hydroxyisophthalic acids were obtained through ball milling experiments. The optimal conditions for the milling process were chosen by changing the solvent volume and the mechanical action time. Supramolecular interactions in the new cocrystals are detailed based on single-crystal X-ray diffraction analysis, confirming the expected formation of hydrogen bonds between the praziquantel carbonyl group and the carboxyl (or hydroxyl) moieties of the coformers. Different structural characterization techniques were performed for all samples, but the praziquantel:suberic acid cocrystal includes a wider range of investigations such as thermal analysis, infrared and X-ray photoelectron spectroscopies, and SEM microscopy. The stability for up to five months was established by keeping it under extreme conditions of temperature and humidity. Solubility studies were carried out for all the new forms disclosed herein and compared with the promising cocrystals previously reported with salicylic, 4-aminosalicylic, vanillic, and oxalic acids. HPLC analyses revealed a higher solubility for most of the new cocrystal forms, as compared to pure praziquantel.publishersversionpublishe

Analytical techniques for multiplex analysis of protein biomarkers

Introduction: The importance of biomarkers for pharmaceutical drug development and clinical diagnostics is more significant than ever in the current shift toward personalized medicine. Biomarkers have taken a central position either as companion markers to support drug development and patient selection, or as indicators aiming to detect the earliest perturbations indicative of disease, minimizing therapeutic intervention or even enabling disease reversal. Protein biomarkers are of particular interest given their central role in biochemical pathways. Hence, capabilities to analyze multiple protein biomarkers in one assay are highly interesting for biomedical research. Areas covered: We here review multiple methods that are suitable for robust, high throughput, standardized, and affordable analysis of protein biomarkers in a multiplex format. We describe innovative developments in immunoassays, the vanguard of methods in clinical laboratories, and mass spectrometry, increasingly implemented for protein biomarker analysis. Moreover, emerging techniques are discussed with potentially improved protein capture, separation, and detection that will further boost multiplex analyses. Expert commentary: The development of clinically applied multiplex protein biomarker assays is essential as multi-protein signatures provide more comprehensive information about biological systems than single biomarkers, leading to improved insights in mechanisms of disease, diagnostics, and the effect of personalized medicine