Analyzing urinary hippuric acid as a metabolic health biomarker through a supramolecular architecture

The prevalence of metabolic disorders has been found to increase concomitantly with alternations in habitual diet and lifestyle, indicating the importance of metabolic health monitoring for early warning of high-risk status and suggesting effective intervention strategies. Hippuric acid (HA), as one of the most abundant metabolites from the gut microbiota, holds potential as a regulator of metabolic health. Accordingly, it is imperative to establish an efficient, sensitive, and affordable method for large-scale population monitoring, revealing the association between HA level and metabolic disorders. Upon systematic screening of macrocycle•dye reporter pair, a supramolecular architecture (guanidinomethyl-modified calix[5]arene, GMC5A) was employed to sense urinary HA by employing fluorescein (Fl), whose complexation behavior was demonstrated by theoretical calculations, accomplishing quantification of HA in urine from 249 volunteers in the range of 0.10 mM and 10.93 mM. Excitedly, by restricted cubic spline, urinary HA concentration was found to have a significantly negative correlation with the risk of metabolic disorders when it exceeded 0.76 mM, suggesting the importance of dietary habits, especially the consumption of fruits, coffee, and tea, which was unveiled from a simple questionnaire survey. In this study, we accomplished a high throughput and sensitive detection of urinary HA based on supramolecular sensing with the GMC5A•Fl reporter pair, which sheds light on the rapid quantification of urinary HA as an indicator of metabolic health status and early intervention by balancing the daily diet.

Mixed host co-assembled systems for broad-scope analyte sensing

Here we report a systems chemistry oriented approach for developing information-rich mixed host chemosensors. We show that co-assembling macrocyclic hosts from different classes, DimerDye sulfonatocalix[4]arenes and cucurbit[n]urils, effectively increases the scope of analyte binding interactions and therefore, sensory outputs. This simple dynamic strategy exploits cross-reactive noncovalent host-host complexation interactions while integrating a reporter dye, thereby producing emergent photophysical responses when an analyte interacts with either host. We first demonstrate the advantages of mixed host co-assembled chemosensors through an increased detection range of hydrophobic, cationic, neutral, and anionic drugs. We then implement mixed host sensors in an array-based platform for the differentiation of illicit drugs, including cannabinoids, benzodiazepine analogs, opiates, anesthetics, amphetamine, and common adulterating substances. Finally, the potential of this approach is applied to profiling real-world multi-component illicit street drug samples, proving to be more effective than classical sensor arrays.

Recent advances in methods for quantifying the cell penetration of macromolecules

As the landscape of macromolecule therapeutics advances, drug developers are continuing to aim at intracellular targets. To activate, inhibit, or degrade these targets, the macromolecule must be delivered efficiently to intracellular compartments. Quite often, there is a discrepancy between binding affinity in biochemical assays and activity in cell-based assays. Identifying the bottleneck for cell-based activity requires robust assays that quantify total cellular uptake and/or cytosolic delivery. Recognizing this need, chemical biologists have designed a plethora of assays to make this measurement, each with distinct advantages and disadvantages. In this review, we describe the latest and most promising developments in the last 3 to 4 years.

Dissimilar effect of organometallic ruthenium complexes on the viability of MDR and non-MDR experimental models

Ruthenium complexes containing triphenylphosphine diamide ligands were prepared, characterized, and tested for their biological activity against various cancer cell lines and the malaria parasite, Plasmodium falciparum. The effect of M (mono-substituted) and B (bis-substituted) complexes on the human cervical carcinoma (HeLa) cell line was investigated using the MTT assay. Five (B2, B3, B5, B6, and B13) of the 24 synthesized ruthenium complexes showed significant effects with IC50 values ranging between 0.3 and 2.3 μM. Evaluation of the potential biomolecular targets of B2 and B13 by fluorescence spectroscopy revealed relevant interactions with BSA and only a weak affinity for ctDNA. Complexes M2, B2, M13 and B13 were selected for further biological characterization. Their effect on the viability of two ovarian cancer cell lines was compared to normal cell lines, denoting their selectivity. Upon treatment of four different drug-resistant gynaecological cancer cell lines, differing in their multidrug-resistant phenotypes, the efficacy of the bis-substituted complexes was shown to be greater than their mono-substituted counterparts. The non-MDR cells are sensitive to all the tested complexes, compared to MDR cells which are less sensitive. Upon investigation of complexes M2, M13, B2, and B13 against sensitive and multidrug-resistant parasite strains of P. falciparum, the bis-substituted complexes were again shown to be the most potent, with submicromolar activity against both strains. Furthermore, the resistance indexes for the complexes were approximately equal to 1, which is at least 5-fold lower than chloroquine diphosphate, suggesting the ability of these complexes to retain their activity in resistant forms of the parasite.

Paper-based optical sensor arrays for simultaneous detection of multi-targets in aqueous media: A review

Sensor arrays, which draw inspiration from the mammalian olfactory system, are fundamental concepts in high-throughput analysis based on pattern recognition. Although numerous optical sensor arrays for various targets in aqueous media have demonstrated their diverse applications in a wide range of research fields, practical device platforms for on-site analysis have not been satisfactorily established. The significant limitations of these sensor arrays lie in their solution-based platforms, which require stationary spectrophotometers to record the optical responses in chemical sensing. To address this, this review focuses on paper substrates as device components for solid-state sensor arrays. Paper-based sensor arrays (PSADs) embedded with multiple detection sites having cross-reactivity allow rapid and simultaneous chemical sensing using portable recording apparatuses and powerful data-processing techniques. The applicability of office printing technologies has promoted the realization of PSADs in real-world scenarios, including environmental monitoring, healthcare diagnostics, food safety, and other relevant fields. In this review, we discuss the methodologies of device fabrication and imaging analysis technologies for pattern recognition-driven chemical sensing in aqueous media.

Harnessing a simple ratiometric fluorescent probe for albumin recognition and beyond

A commercially available naphthalene fluorophore serves as a ratiometric indicator for albumin, showcasing its applications in albumin-based supramolecular recognition.

Expanding the Hydrophobic Cavity Surface of Azocalix[4]arene to Enable Biotin/Avidin Affinity with Controlled Release

The development of artificial receptors that combine ultrahigh-affinity binding and controllable release for active guests holds significant importance in biomedical applications. On one hand, a complex with an exceedingly high binding affinity can resist unwanted dissociation induced by dilution effect and complex interferents within physiological environments. On the other hand, stimulus-responsive release of the guest is essential for precisely activating its function. In this context, we expanded hydrophobic cavity surface of a hypoxia-responsive azocalix[4]arene, affording Naph-SAC4A. This modification significantly enhanced its aqueous binding affinity to 1013 M-1, akin to the naturally occurring strongest recognition pair, biotin/(strept-)avidin. Consequently, Naph-SAC4A emerges as the first artificial receptor to simultaneously integrate ultrahigh recognition affinity and actively controllable release. The markedly enhanced affinity not only improved Naph-SAC4A's sensitivity in detecting rocuronium bromide in serum, but also refined the precision of hypoxia-responsive doxorubicin delivery at the cellular level, demonstrating its immense potential for diverse practical applications.

Antimicrobial macrozones interact with biological macromolecules via two-site binding mode of action: Fluorimetric, NMR and docking studies

Macrozones are novel conjugates of azithromycin and thiosemicarbazones, which exhibit very good in vitro antibacterial activities against susceptible and some resistant bacterial strains thus showing a potential for further development. A combination of spectrometric (fluorimetry, STD and WaterLOGSY NMR) and molecular docking studies provided insights into atomic details of interactions between selected macrozones and biological receptors such as E. coli ribosome and bovine serum albumin. Fluorimetric measurements revealed binding constants in the micro-molar range while NMR experiments provided data on binding epitopes. It has been demonstrated that both STD and WaterLOGSY gave comparable and consistent results unveiling atoms in intimate contacts with biological receptors. Docking studies pointed towards main interactions between macrozones and E. coli ribosome which included specific π - π stacking and hydrogen bonding interactions with thiosemicarbazone part extending down the ribosome exit tunnel. The results of the docking experiments were in fine correlation with those obtained by NMR and fluorimetry. Our investigation pointed towards a two-site binding mechanism of interactions between macrozones and E. coli ribosome which is the most probable reason for their activity against azithromycin-resistant strains. Much better activity of macrozone-nickel coordinated compound against E. coli ribosome compared to other macrozones has been attributed to the higher polarity which enabled better bacterial membrane penetration and binding of the two thiosemicarbazone units thus additionally contributing to the overall binding energy. The knowledge gained in this study should play an important role in anti-infective macrolide design in the future.

Nanosensor based approaches for quantitative detection of heparin

Heparin, being a widely employed anticoagulant in numerus clinical complications, requires strict quantification and qualitative screening to ensure the safety of patients from potential threat of thrombocytopenia. However, the intricacy of heparin's chemical structures and low abundance hinders the precise monitoring of its level and quality in clinical settings. Conventional laboratory assays have limitations in sensitivity and specificity, necessitating the development of innovative approaches. In this context, nanosensors emerged as a promising solution due to enhanced sensitivity, selectivity, and ability to detect heparin even at low concentrations. This review delves into a range of sensing approaches including colorimetric, fluorometric, surface-enhanced Raman spectroscopy, and electrochemical techniques using different types of nanomaterials, thus providing insights of its principles, capabilities, and limitations. Moreover, integration of smart-phone with nanosensors for point of care diagnostics has also been explored. Additionally, recent advances in nanopore technologies, artificial intelligence (AI) and machine learning (ML) have been discussed offering specificity against contaminants present in heparin to ensure its quality. By consolidating current knowledge and highlighting the potential of nanosensors, this review aims to contribute to the advancement of efficient, reliable, and economical heparin detection methods providing improved patient care.

Optical discrimination of terpenes in citrus peels with a host:guest sensing array

A simple aqueous host:guest sensing array can selectively discriminate between different types of citrus varietal from peel extract samples. It can also distinguish between identical citrus samples at varying stages of ripening. The discrimination effects stem from detection of changes in the terpenoid composition of the peel extracts by the host:guest array, despite the overwhelming excess of a single component, limonene, in each sample. The hosts are insensitive to limonene but bind other monoterpenes strongly, even though they are similar in structure to the major limonene component. This work demonstrates the capability of host:guest arrays in sensing target molecules in environments with the competing agents present at high abundances in the sample matrix.

Molecular machines working at interfaces: physics, chemistry, evolution and nanoarchitectonics

As a post-nanotechnology concept, nanoarchitectonics combines nanotechnology with advanced materials science. Molecular machines made by assembling molecular units and their organizational bodies are also products of nanoarchitectonics. They can be regarded as the smallest functional materials. Originally, studies on molecular machines analyzed the average properties of objects dispersed in solution by spectroscopic methods. Researchers' playgrounds partially shifted to solid interfaces, because high-resolution observation of molecular machines is usually done on solid interfaces under high vacuum and cryogenic conditions. Additionally, to ensure the practical applicability of molecular machines, operation under ambient conditions is necessary. The latter conditions are met in dynamic interfacial environments such as the surface of water at room temperature. According to these backgrounds, this review summarizes the trends of molecular machines that continue to evolve under the concept of nanoarchitectonics in interfacial environments. Some recent examples of molecular machines in solution are briefly introduced first, which is followed by an overview of studies of molecular machines and similar supramolecular structures in various interfacial environments. The interfacial environments are classified into (i) solid interfaces, (ii) liquid interfaces, and (iii) various material and biological interfaces. Molecular machines are expanding their activities from the static environment of a solid interface to the more dynamic environment of a liquid interface. Molecular machines change their field of activity while maintaining their basic functions and induce the accumulation of individual molecular machines into macroscopic physical properties molecular machines through macroscopic mechanical motions can be employed to control molecular machines. Moreover, research on molecular machines is not limited to solid and liquid interfaces; interfaces with living organisms are also crucial.

Circular Dichroism Sensing: Strategies and Applications

The analysis of the absolute configuration, enantiomeric composition, and concentration of chiral compounds are frequently encountered tasks across the chemical and health sciences. Chiroptical sensing methods can streamline this work and allow high-throughput screening with remarkable reduction of operational time and cost. During the last few years, significant methodological advances with innovative chirality sensing systems, the use of computer-generated calibration curves, machine learning assistance, and chemometric data processing, to name a few, have emerged and are now matched with commercially available multi-well plate CD readers. These developments have reframed the chirality sensing space and provide new opportunities that are of interest to a large group of chemists. This review will discuss chirality sensing strategies and applications with representative small-molecule CD sensors. Emphasis will be given to important milestones and recent advances that accelerate chiral compound analysis by outperforming traditional methods, conquer new directions, and pioneering efforts that lie at the forefront of chiroptical high-throughput screening developments. The goal is to provide the reader with a thorough understanding of the current state and a perspective of future directions of this rapidly emerging field.

Food for Thought: Optical Sensor Arrays and Machine Learning for the Food and Beverage Industry

Arrays of cross-reactive sensors, combined with statistical or machine learning analysis of their multivariate outputs, have enabled the holistic analysis of complex samples in biomedicine, environmental science, and consumer products. Comparisons are frequently made to the mammalian nose or tongue and this perspective examines the role of sensing arrays in analyzing food and beverages for quality, veracity, and safety. I focus on optical sensor arrays as low-cost, easy-to-measure tools for use in the field, on the factory floor, or even by the consumer. Novel materials and approaches are highlighted and challenges in the research field are discussed, including sample processing/handling and access to significant sample sets to train and test arrays to tackle real issues in the industry. Finally, I examine whether the comparison of sensing arrays to noses and tongues is helpful in an industry defined by human taste.

Ratiometric determination of etomidate based on an albumin-based indicator displacement assay (IDA)

The first fluorescent sensor based on the indicator displacement assay (IDA) for on-site determination of etomidate.

Squaramide-based receptors in anion supramolecular chemistry: insights into anion binding, sensing, transport and extraction

Over the last 15 years, squaramide-based receptors have attracted the attention of supramolecular chemists working in the field of anion recognition. Herein, we highlight examples of squaramide-based receptors that are able to bind, sense, extract and transport anions.

Targeting MicroRNAs with Small Molecules

MicroRNAs (miRs) have been implicated in numerous diseases, presenting an attractive target for the development of novel therapeutics. The various regulatory roles of miRs in cellular processes underscore the need for precise strategies. Recent advances in RNA research offer hope by enabling the identification of small molecules capable of selectively targeting specific disease-associated miRs. This understanding paves the way for developing small molecules that can modulate the activity of disease-associated miRs. Herein, we discuss the progress made in the field of drug discovery processes, transforming the landscape of miR-targeted therapeutics by small molecules. By leveraging various approaches, researchers can systematically identify compounds to modulate miR function, providing a more potent intervention either by inhibiting or degrading miRs. The implementation of these multidisciplinary approaches bears the potential to revolutionize treatments for diverse diseases, signifying a significant stride towards the targeting of miRs by precision medicine.

Water-Soluble Triazolium Covalent Cages for ATP Sensing

Water-soluble organic cages are attractive targets for their molecular recognition and sensing features of biologically relevant molecules. Here, we have successfully designed and synthesized a pair of water-soluble cationic cages employing click reaction as the fundamental step followed by the N-methylation of the triazole rings. The rigid and shape-persistent 3D hydrophobic cavity, positively charged surface, H-bonding triazolium rings, and excellent water solubility empower both cages to exhibit a superior affinity and selectivity for binding with adenosine-5'-triphosphate (ATP) compared to cyclophanes and other macrocyclic receptors. Both cage molecules (PCC⋅Cl and BCC⋅Cl) can bind a highly emissive dye HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt) to form non-fluorescent complexes. The addition of ATP resulted in the stronger cage⊂ATP complexes with the retention of HPTS emission upon its displacement. The resultant indicator-displacement assay system can efficiently sense and quantify ATP in nanomolar detection limits in buffer solutions and human serum matrix. Spectroscopic and theoretical studies revealed the synergistic effect of π⋅⋅⋅π stacking interaction between the aromatic moiety of the cationic cages and the adenine moiety of ATP, as well as the electrostatic and hydrogen bonding interaction between the phosphate anion of ATP and triazole protons of cages, played the pivotal roles in the sensing process.

Fast, portable, selective, and ratiometric determination of ochratoxin A (OTA) by a fluorescent supramolecular sensor

Ochratoxin A (OTA), a mycotoxin found in various food items, possesses significant health risks due to its carcinogenic and toxic properties. Thus, detecting OTA is crucial to ensure food safety. Among the reported analytical methods, there has yet to be one that achieves fast, selective, and portable detection of OTA. In this study, we explore a novel supramolecular sensor, DOCE@ALB, utilizing human serum albumin as the host and a flavonoid fluorescent indicator as the guest. On the basis of indicator displacement assay, this sensor boasts an ultra-fast response time of just 5 s, high sensitivity with a limit of detection at 0.39 ppb, exceptional selectivity, and a noticeable ratiometric fluorescence response to OTA. This discernible color change and portability of the sensor make it suitable for on-site OTA detection in real food samples, including flour, beer, and wine, simply using a smartphone. In comparison to previously reported methods, our approach has showcased notable advantages in both response time and portability, addressing a critical need for food safety and regulatory compliance.

A ratiometric fluorescent indicator-displacement assay for on-site determination and intracellular imaging of nitroxinil

Nitroxinil (NIT) is a widely using veterinary medicine to protect cattle and sheep yet may threaten human health when ingested through food chain. Developing fluorescent analytical methods in ratiometric manners was essential for the on-site detection and in-situ monitoring of NIT but still challenging. Here, we improved the indicator-displacement assay (IDA)-based method and designed the first ratiometric fluorescent probe for NIT by using an albumin host and an Aggregation-induced emission (AIE) guest. This probe exhibited fast response (10 s), high sensitivity (limit of detection: 4.6 ppb), good selectivity (over twelve medicines) and eye-discriminable fluorescent color change (green-red) upon responding to NIT. Based on these properties, this probe enabled quantitative determination of NIT in real food samples, on-site analysis via a paper-based test strip, and fluorescence imaging of NIT in living cells.

Fluorescent ratiometric supramolecular tandem assays for phosphatase and phytase enzymes

Ratiometric fluorescent assays have a built-in correction factor which enhances assay accuracy and reliability. We have developed fluorescent ratiometric supramolecular tandem assays for phosphatase and phytase enzymes using a mixture of three molecular components. One of the molecules is a tetra-cationic fluorescence quencher called CalixPyr which can bind and quench the polyanionic pyrene fluorophore, CMP, that emits at 430 nm. Polyphosphates can disrupt the CMP/CalixPyr complex and alter the fluorescence intensity (responsive signal). CalixPyr has no effect on the fluorescence emission of cationic pentamethine cyanine fluorophore, cCy5, which emits at 665 nm and acts as a non-responsive reference signal. The continuous ratiometric fluorescent assay for alkaline phosphatase monitored hydrolytic consumption of adenosine triphosphate (ATP). The continuous ratiometric fluorescent assay for phytase activity monitored hydrolytic consumption of phytate. With further development this latter assay may be useful for high throughput assessment of phytase activity in individual batches of fortified animal feed. It is likely that the three-molecule mixture (CMP, CalixPyr, cCy5) can become a general assay platform for other enzymes that catalyse addition/removal of phosphate groups from appropriate molecular substrates.

Overcoming barriers with non-covalent interactions: supramolecular recognition of adamantyl cucurbit[n]uril assemblies for medical applications

Adamantane, a staple in medicinal chemistry, recently became a cornerstone of a supramolecular host-guest drug delivery system, ADA/CB[n]. Owing to a good fit between the adamantane cage and the host cavity of the cucurbit[n]uril macrocycle, formed strong inclusion complexes find applications in drug delivery and controlled drug release. Note that the cucurbit[n]uril host is not solely a delivery vehicle of the ADA/CB[n] system but rather influences the bioactivity and bioavailability of drug molecules and can tune drug properties. Namely, as host-guest interactions are capable of changing the intrinsic properties of the guest molecule, inclusion complexes can become more soluble, bioavailable and more resistant to metabolic conditions compared to individual non-complexed molecules. Such synergistic effects have implications for practical bioapplicability of this complex system and provide a new viewpoint to therapy, beyond the traditional single drug molecule approach. By achieving a balance between guest encapsulation and release, the ADA/CB[n] system has also found use beyond just drug delivery, in fields like bioanalytics, sensing assays, bioimaging, etc. Thus, chemosensing in physiological conditions, indicator displacement assays, in vivo diagnostics and hybrid nanostructures are just some recent examples of the ADA/CB[n] applicability, be it for displacements purposes or as cargo vehicles.

FRET-Based Host-Guest Supramolecular Probe for On-Site and Broad-Spectrum Detection of Pyrethroids in the Environment

The massive use of pyrethroid pesticides in agriculture has brought growing concerns about food safety due to their several harmful effects on human health, especially through the accumulation of the food chain. To date, most of the available analytical methods for pyrethroids still suffer from insufficient detection universality, complicated sample pretreatment, and detection processes, which severely limit their practical applications. Herein, a novel Förster resonance energy transfer (FRET)-assisted host-guest supramolecular nanoassembly is reported, for the first time, successfully realizing ratiometric fluorescent detection of pyrethroids in real samples through the indicator displacement assay (IDA) mechanism. This method is capable of detecting a broad spectrum of pyrethroids, including bifenthrin, cyfluthrin, cypermethrin, deltamethrin, etofenprox, fenvalerate, and permethrin, with ultrahigh detection sensitivity, great selectivity, high anti-interference ability, and, in particular, distinct emission color response from red to green. Such a large chromatic response makes this method available for fast and on-site detection of pyrethroids in real samples with the aid of several simple portable analytical apparatuses.

Host-Guest Chemosensor Ensembles based on Water-Soluble Sulfonated Calix[n]arenes and a Pyranoflavylium Dye for the Optical Detection of Biogenic Amines

Biogenic amines (BAs) are biologically active nitrogen-containing compounds formed during the food spoilage process and are often related as key markers of food quality, safety, and freshness. Because their presence in foods at high levels can cause significant health problems, researchers have been focused on developing novel strategies and methods for early detection and capture of these analytes. Herein, water-soluble sulfonated calix[n]arene macrocycles (SC4, SC6, and SC8) and a pH-sensitive dye (4'-hydroxy-10-methylpyranoflavylium) were investigated as host-guest systems for BA sensing. The hosts were able to bind the flavylium cation of the dye with association constants of 103 to 104 M-1. The dye complexation also allowed tuning its pKa from 6.72 (free) toward high values: 7.68 (SC4), 7.79 (SC6), and 8.45 (SC8). These data were crucial to optimize the host-guest complexes as optical sensing systems for putrescine/tyramine (pH 7.2-7.6), yielding a colorimetric redshift from yellow to red. The BA sensing was also demonstrated by fluorescence quenching for the calix[n]arene/dye complexes and fluorescence recovery after the addition of BAs. 1H NMR spectroscopy was used to demonstrate the interaction mode, confirming an encapsulation-driven mechanism. Overall, these host-guest systems demonstrated great potential for the detection of BAs, one of the main key markers of food spoilage.

Selective recognition and discrimination of single isomeric changes in peptide strands with a host : guest sensing array

An indirect competitive binding mechanism can be exploited to allow a combination of cationic fluorophores and water-soluble synthetic receptors to selectively recognize and discriminate peptide strands containing a single isomeric residue in the backbone. Peptide isomerization occurs in long-lived proteins and has been linked with diseases such as Alzheimer's, cataracts and cancer, so isomers are valuable yet underexplored targets for selective recognition. Planar cationic fluorophores can selectively bind hydrophobic, Trp-containing peptide strands in solution, and when paired with receptors that provide a competitive host for the fluorophore, can form a differential sensing array that enables selective discrimination of peptide isomers. Residue variations such as D- and L-Asp, D- and L-isoAsp, D-Ser and D-Glu can all be recognized, simply by their effects on the folded structure of the flexible peptide. Molecular dynamics simulations were applied to determine the most favorable conformation of the peptide : fluorophore conjugate, indicating that favorable π-stacking with internal tryptophan residues in a folded binding pocket enables micromolar binding affinity.

Multilocus Distance-Regulated Sensor Array for Recognition of Polyphenols via Machine Learning and Indicator Displacement Assay

Developing new strategies to construct sensor arrays that can effectively distinguish multiple natural components with similar structures in mixtures is an exceptionally challenging task. Here, we propose a new multilocus distance-modulated indicator displacement assay (IDA) strategy for constructing a sensor array, incorporating machine learning optimization to identify polyphenols. An 8-element array, comprising two fluorophores and their six dynamic covalent complexes (C1-C6) formed by pairing two fluorophores with three distinct distance-regulated quenchers, has been constructed. Polyphenols with diverse spatial arrangements and combinatorial forms compete with the fluorophores by forming pseudocycles with quenchers within the complexes, leading to varying degrees of fluorescence recovery. The array accurately and effectively distinguished four tea polyphenols and 16 tea varieties, thereby demonstrating the broad applicability of the multilocus distance-modulated IDA array in detecting polyhydroxy foods and natural medicines.

Fluorescence determination of the total amount of tetracyclines by a flavonol-based supramolecular sensor

Tetracyclines (TCs) are a group of broad-spectrum antibiotics against multiplying microorganisms yet with several adverse effects on humans. Since all types of TCs have the similar chemical skeleton and mechanism of action, quantification of total amount of TCs in the environment was of particular importance. To date, dozens of fluorescent probes have been reported for TCs detection, but only very few of them enabled detection of total TCs. In this study, we report a novel supramolecular sensor constructed by human serum albumin as the recognition moiety and a flavonol fluorophore as the indicator. Under the 370 nm UV excitation, this sensor exhibits the rapid response (5 s), acceptable sensitivity (limit of detection ∼ 0.58 μM), long dynamic detection range (0-20 μM), prominent specificity, and excellent anti-interference properties for analysis of total TCs. The mechanism was carefully validated using 1H NMR, fluorescence titration experiments, molecular docking, and mass spectrometry. We expect this work can inspire more sensor design for TCs quantification.

Dual-Color Real-Time Chemosensing of a Compartmentalized Reaction Network Involving Enzyme-Induced Membrane Permeation of Peptides

The design of synthetic systems with interrelated reaction sequences that model incipient biological complexity is limited by physicochemical tools that allow the direct monitoring of the individual processes in real-time. To mimic a simple digestion-resorption sequence, the authors have designed compartmentalized liposomal systems that incorporate extra- and intravesicular chemosensing ensembles. The extravesicular reporter pair consists of cucurbit[7]uril and methylene blue to monitor the enzymatic cleavage of short enkephalin-related peptides by thermolysin through a switch-off fluorescence response ("digestion"). Because the substrate is membrane-impermeable, but the dipeptide product is permeable, uptake of the latter into the pre-formed liposomes occurs as a follow-up process. The intravesicular chemosensing ensemble consists of i) cucurbit[8]uril, 2-anilinonaphthalene-6-sulfonic acid, and methyl viologen or ii) cucurbit[7]uril and berberine to monitor the uptake ("resorption") of the enzymatic products through the liposomal membranes by i) a switch-on or ii) a switch-off fluorescence response. The dyes are designed to allow selective optical excitation and read-out of the extra- and intravesicular dyes, which allow for dual-color chemosensing and, therefore, kinetic discrimination of the two sequential reactions.

Emerging sensing platforms based on Cucurbit[n]uril functionalized gold nanoparticles and electrodes

Cucurbit[n]urils (CB[n]s, n = 5-8, 10, and 14), synthetic macrocycles with unique host-guest properties, have triggered increasing research interest in recent years. Gold nanoparticles (Au NPs) and electrodes stand out as exceptional substrates for sensing due to their remarkable physicochemical characteristics. Coupling the CB[n]s with Au NPs and electrodes has enabled the development of emerging sensing platforms for various promising applications. However, monitoring the behavior of analytes at the single-molecule level is currently one of the most challenging topics in the field of CB[n]-based sensing. Constructing supramolecular junctions in a sensing platform provides an ideal structure for single-molecule analysis, which can provide insights for a fundamental understanding of supramolecular interactions and chemical reactions and guide the design of sensing applications. This feature article outlines the progress in the preparation of the CB[n] functionalized Au NPs and Au electrodes, as well as the construction and application of supramolecular junctions in sensing platforms, based on the methods of recognition tunneling (RT), surface-enhanced Raman spectroscopy (SERS), single-molecule force spectroscopy (SMFS), and electrochemical sensing (ECS). A brief perspective on the future development of and challenges in CB[n] mediated sensing platforms is also covered.

Navigating the Expansive Landscapes of Soft Materials: A User Guide for High-Throughput Workflows

Synthetic polymers are highly customizable with tailored structures and functionality, yet this versatility generates challenges in the design of advanced materials due to the size and complexity of the design space. Thus, exploration and optimization of polymer properties using combinatorial libraries has become increasingly common, which requires careful selection of synthetic strategies, characterization techniques, and rapid processing workflows to obtain fundamental principles from these large data sets. Herein, we provide guidelines for strategic design of macromolecule libraries and workflows to efficiently navigate these high-dimensional design spaces. We describe synthetic methods for multiple library sizes and structures as well as characterization methods to rapidly generate data sets, including tools that can be adapted from biological workflows. We further highlight relevant insights from statistics and machine learning to aid in data featurization, representation, and analysis. This Perspective acts as a "user guide" for researchers interested in leveraging high-throughput screening toward the design of multifunctional polymers and predictive modeling of structure-property relationships in soft materials.

Adaptive Supramolecular Networks: Emergent Sensing from Complex Systems

Molecular differentiation by supramolecular sensors is typically achieved through sensor arrays, relying on the pattern recognition responses of large panels of isolated sensing elements. Here we report a new one-pot systems chemistry approach to differential sensing in biological solutions. We constructed an adaptive network of three cross-assembling sensor elements with diverse analyte-binding and photophysical properties. This robust sensing approach exploits complex interconnected sensor-sensor and sensor-analyte equilibria, producing emergent supramolecular and photophysical responses unique to each analyte. We characterize the basic mechanisms by which an adaptive network responds to analytes. The inherently data-rich responses of an adaptive network discriminate among very closely related proteins and protein mixtures without relying on designed protein recognition elements. We show that a single adaptive sensing solution provides better analyte discrimination using fewer response observations than a sensor array built from the same components. We also show the network's ability to adapt and respond to changing biological solutions over time.

Enantioselective and Chemoselective Optical Detection of Chiral Organic Compounds without Resorting to Chromatography

Enantiorecognition and resolution are of essential importance in many diverse areas of science. Whenever there arises a need to analyze/investigate enantiomers in different situations chromatography stands up in our minds immediately. Nevertheless, chemoselective and enantioselective recognition/discrimination (without going for separation) constitutes a different perception and requirement. The techniques using chiroptical sensing cause detection based on molecular interactions induced in different manners. Enantioselective sensing of monosaccharides in γ-cyclodextrin assembly and by diboronic acid based fluorescent sensors, application of bi-naphthol and H8 BINOL based sensors and dendrimers, metal-to-ligand charge transfer transitions in CD, exciton-coupled circular dichroism, surface enhanced Raman spectroscopy, and enantioselective indicator displacement sensor arrays for enantioselective recognition/detection of chiral organic compounds, such as amines, amino acids/alcohols, and hydroxycarboxylic acids have been discussed in progressive manner with mechanistic explanations, wherever available. Besides, the chiroptical vs LC approach has been discussed. The present paper is focused on certain different non-chromatographic optical techniques and aims to extend an understanding and a view to consider such techniques which have been successful in selective detection, and determination of absolute configuration and enantiomeric excess, (without resorting to separation vis-à-vis LC) and that have potential use in high-throughput chiral assay and combinatorial search for asymmetric catalysts and reagents.

Dual reactivity based dynamic covalent chemistry: mechanisms and applications

Dynamic covalent chemistry (DCC) focuses on the reversible formation, breakage, and exchange of covalent bonds and assemblies, setting a bridge between irreversible organic synthesis and supramolecular chemistry and finding wide utility. In order to enhance structural and functional diversity and complexity, different types of dynamic covalent reactions (DCRs) are placed in one vessel, encompassing orthogonal DCC without crosstalk and communicating DCC with a shared reactive functional group. As a means of adding tautomers, widespread in chemistry, to interconnected DCRs and combining the features of orthogonal and communicating DCRs, a concept of dual reactivity based DCC and underlying structural and mechanistic insights are summarized. The manipulation of the distinct reactivity of structurally diverse ring-chain tautomers allows selective activation and switching of reaction pathways and corresponding DCRs (C-N, C-O, and C-S) and assemblies. The coupling with photoswitches further enables light-mediated formation and scission of multiple types of reversible covalent bonds. To showcase the capability of dual reactivity based DCC, the versatile applications in dynamic polymers and luminescent materials are presented, paving the way for future functionalization studies.

Binding affinity-based intracellular drug detection enabled by a unimolecular cucurbit[7]uril-dye conjugate

Label-free fluorescence-based chemosensing has been increasingly brought into focus due to its simplicity and high sensitivity for intracellular monitoring of molecules. Currently used methods, such as conventional indicator displacement assays (IDAs), pose limitations related to dissociation upon dilution, random diffusion of the released indicators, and high sensitivity to interference by agents from the ambient cellular environment (e.g., salts, enzymes, and proteins). Herein we report a potentially widely applicable strategy to overcome the limitations of conventional IDAs by employing a macrocyclic cucurbit[7]uril (CB7) host covalently coupled to a nitrobenzoxadiazole (NBD) fluorescent dye (CB7-NBD conjugate). As a proof of concept, we demonstrated that the CB7-NBD unimolecular conjugate responded to various target analytes even in the complex live cell system. Moreover, the sensing system was compatible with fluorescence imaging, fluorescence-assisted cell sorting (FACS), and fluorescence spectrometry with a microplate reader. These experiments demonstrated an application of covalently bound unimolecular CB7-NBD conjugate as a sensor for detecting diverse analytes in the intracellular compartment of live cells.

Progress in optical sensors-based uric acid detection

The escalating number of patients affected by various diseases, such as gout, attributed to abnormal uric acid (UA) concentrations in body fluids, has underscored the need for rapid, efficient, highly sensitive, and stable UA detection methods and sensors. Optical sensors have garnered significant attention due to their simplicity, cost-effectiveness, and resistance to electromagnetic interference. Notably, research efforts have been directed towards UA on-site detection, enabling daily monitoring at home and facilitating rapid disease screening in the community. This review aims to systematically categorize and provide detailed descriptions of the notable achievements and emerging technologies in UA optical sensors over the past five years. The review highlights the advantages of each sensor while also identifying their limitations in on-site applications. Furthermore, recent progress in instrumentation and the application of UA on-site detection in body fluids is discussed, along with the existing challenges and prospects for future development. The review serves as an informative resource, offering technical insights and promising directions for future research in the design and application of on-site optical sensors for UA detection.

Enzymatic colorimetric method for turn-on determination of l-lactic acid through indicator displacement assay

l-Lactic acid is a natural α-hydroxy carboxylic acid and is commonly used as an addictive. Quantitation of l-lactic acid is indispensable in food and cosmetic industries. An enzymatic colorimetric method was developed for the determination of l-lactic acid by competitive indicator displacement assay. Boric acid inhibited the colorimetric reaction of l-3,4-dihydroxyphenylalanine (l-DOPA) catalyzed by tyrosinase. l-Lactic acid competitively displaced and released l-DOPA bound with boric acid to serve as substrate, and thus restored the tyrosinase activity. Recovery of color reaction could be spectrophotometrically determined at 475 nm and was proportional to the amount of l-lactic acid. A calibration curve between l-lactic acid concentration and recovery of absorbance were built. The concentration range of the l-lactic acid was 0.25-2.25 mM. The limit of detection (LOD) and the limit of quantification (LOQ) for l-lactic acid was estimated to be 0.05 mM and 0.16 mM, respectively. The method achieved turn-on and visual sensing with good precision, accuracy, specificity, and robustness. The assay method exhibited a promising prospect to determine the content of l-lactic acid in foods and cosmetics.

Novel Tripodal Polyamine Tris-Pyrene: DNA/RNA Binding and Photodynamic Antiproliferative Activity

A novel tri-pyrene polyamine (TAL3PYR) bearing net five positive charges at biorelevant conditions revealed strong intramolecular interactions in aqueous medium between pyrenes, characterised by pronounced excimer fluorescence. A novel compound revealed strong binding to ds-DNA and ds-RNA, along with pronounced thermal stabilisation of DNA/RNA and extensive changes in DNA/RNA structure, as evidenced by circular dichroism. New dye caused pronounced ds-DNA or ds-RNA condensation, which was attributed to a combination of electrostatic interactions between 5+ charge of dye and negatively charged polynucleotide backbone, accompanied by aromatic and hydrophobic interactions of pyrenes within polynucleotide grooves. New dye also showed intriguing antiproliferative activity, strongly enhanced upon photo-induced activation of pyrenes, and is thus a promising lead compound for theranostic applications on ds-RNA or ds-DNA targets, applicable as a new strategy in cancer and gene therapy.

Selective Molecular Recognition and Indicator Displacement Sensing of Neurotransmitters in Cellular Environments

Flexible, water-soluble hosts are capable of selective molecular recognition in cellular environments and can detect neurotransmitters such as choline in cells. Both cationic and anionic water-soluble self-folded deep cavitands can recognize suitable styrylpyridinium dyes in cellular interiors. The dyes selectively accumulate in nucleotide-rich regions of the cell nucleus and cytoplasm. The hosts bind the dyes and promote their relocation to the outer cell membrane: the lipophilic cavitands predominantly reside in membrane environments but are still capable of binding suitable targets in other cellular organelles. Incubating the cells with structurally similar biomarkers such as choline, cholamine, betaine, or butyrylcholine illustrates the selective recognition. Choline and butyrylcholine can be bound by the hosts, but minimal binding is seen with betaine or cholamine. Varying the dye allows control of the optical detection method, and both "turn-on" sensing and "turn-off" sensing are possible.

Pattern Recognition and Visual Detection of Aldehydes Using a Single ESIPT Dye

The accurate discrimination and quantification of aldehydes is a worthy objective made challenging by their similar chemical reactivities. Considering the nucleophilic reaction mechanism between an aldehyde and a primary amine, it is reasonable to vary the reaction pH to manipulate the reactivity of aldehydes and the stability of the resulting Schiff base for analytical purposes. We have designed and synthesized three benzothiazole-based fluorescent molecules (BS1-BS3) containing an amino group substituted at the ortho-, meta-, and para-positions for aldehyde sensing. It was determined that only BS1 having an amino group at the ortho-position exhibits a significant fluorescence response in the presence of formaldehyde at a particular pH, whereas BS2 and BS3 gave negligible responses, indicating that the ESIPT process in BS1 should be responsible for the changes in its fluorescence. Accordingly, a pH-mediated sensor array BS1SA was constructed by dissolving BS1 in aqueous solvents with different pH values. BS1SA was found to be reliable for the discrimination of seven different aldehydes and identification of unknown aldehyde samples. Moreover, BS1 was successfully applied to prepare a fluorescent test paper for the visual detection of formaldehyde vapor.

Turn-on fluorescence of ruthenium pyrene complexes in response to bovine serum albumin

Two novel pyrene triphenylphosphine ruthenium conjugates act as fluorescent turn-on beacons for serum albumin, being non-fluorescent in aqueous media but exhibiting strong emission upon binding to BSA. The selective cytotoxicity of the compounds against tumour cells is enhanced upon irradiation by UV-light, paving the way for application in photodynamic therapy under two-photon excitation.

Sensitive and specific detection of saccharide species based on fluorescence: update from 2016

Increasing evidence supports the critical role of saccharides in various pathophysiological steps of tumor progression, where they regulate tumor proliferation, invasion, hematogenic metastasis, and angiogenesis. The identification and recognition of these saccharides provide a solid foundation for the development of targeted drug preparations, which are however not fully understood due to their complex and similar structures. In order to achieve fluorescence sensing of saccharides, extensive research has been conducted to design molecular probes and nanoparticles made of different materials. This paper aims to provide in-depth discussion of three main topics that cover the current status of the carbohydrate sensing based on the fluorescence sensing mechanism, including a phenylboronic acid-based sensing platform, non-boronic acid entities, as well as an enzyme-based sensing platform. It also highlights efforts made to understand the recognition mechanisms and improve the sensing properties of these systems. Finally, we present the challenge of achieving high selectivity and sensitivity recognition of saccharides, and suggest possible future avenues for exploration.

Optical sensor arrays for the detection and discrimination of natural products

Covering: up to the end of 2022Natural products (NPs) have found uses in medicine, food, cosmetics, materials science, environmental protection, and other fields related to our life. Their beneficial properties along with potential toxicities make the detection and discrimination of NPs crucial for their applications. Owing to the merits of low cost and simple operation, optical sensor arrays, including colorimetric and fluorometric sensor arrays, have been widely applied in the detection of small molecule NPs and discrimination of structurally similar small molecule NPs or complex mixtures of NPs. This review provides a brief introduction to the optical sensor array and focuses on its progress toward the detection and discrimination of NPs. We summarized the design principle of sensor arrays toward various NPs (i.e., saccharides and polyhydroxy compounds, organic acids, flavonoids, organic sulfur compounds, amines, amino acids, and saponins) based on their functional groups and characteristic chemical properties, along with representative examples. Moreover, the challenges and potential directions for further research of optical sensor arrays for NPs are proposed.

Supramolecular chiral sensing by supramolecular helical polymers

A tetrakis(porphyrin) with branched side chains self-assembled to form supramolecular helical polymers both in solution and in the solid state. The helicity of the supramolecular polymers was determined by the chirality of solvent molecules, which permitted the polymer chains to be used in chiral sensing.

Converting pH probes into "turn-on" fluorescent receptors for anions

Recognition of anions by synthetic receptors is an integral part of supramolecular chemistry continuing to expand and find new application areas in our daily life. Many applications require visualization of anion recognition events, and the generated analytical signal is used to quantify anions in solution. Transferring a binding event to a measured signal is a challenging task. The design of a synthetic receptor must involve not only the perfectly positioned binding sites with complementary noncovalent interactions for a guest but should also realize the sensing mechanism that generates a strong analytical response upon guest binding. This feature article outlines the design concept for the construction of "turn-on" fluorescent receptors for anions involving fluorescent pH probes. Applications of this concept for the construction of synthetic fluorescent receptors for inorganic anions and nucleotides are described. Features of the obtained receptors and possible competing binding and sensing processes in solution are analyzed to understand the scope and limitations of the approach.

Fluorescent probes for the detection of chemical warfare agents

Chemical warfare agents (CWAs) are toxic chemicals that have been intentionally developed for targeted and deadly use on humans. Although intended for military targets, the use of CWAs more often than not results in mass civilian casualties. To prevent further atrocities from occurring during conflicts, a global ban was implemented through the chemical weapons convention, with the aim of eliminating the development, stockpiling, and use of CWAs. Unfortunately, because of their relatively low cost, ease of manufacture and effectiveness on mass populations, CWAs still exist in today's world. CWAs have been used in several recent terrorist-related incidents and conflicts (e.g., Syria). Therefore, they continue to remain serious threats to public health and safety and to global peace and stability. Analytical methods that can accurately detect CWAs are essential to global security measures and for forensic analysis. Small molecule fluorescent probes have emerged as attractive chemical tools for CWA detection, due to their simplicity, ease of use, excellent selectivity and high sensitivity, as well as their ability to be translated into handheld devices. This includes the ability to non-invasively image CWA distribution within living systems (in vitro and in vivo) to permit in-depth evaluation of their biological interactions and allow potential identification of therapeutic countermeasures. In this review, we provide an overview of the various reported fluorescent probes that have been designed for the detection of CWAs. The mechanism for CWA detection, change in optical output and application for each fluorescent probe are described in detail. The limitations and challenges of currently developed fluorescent probes are discussed providing insight into the future development of this research area. We hope the information provided in this review will give readers a clear understanding of how to design a fluorescent probe for the detection of a specific CWA. We anticipate that this will advance our security systems and provide new tools for environmental and toxicology monitoring.

Recent advances in fluorescent and colorimetric chemosensors for the detection of chemical warfare agents: a legacy of the 21st century

Chemical warfare agents (CWAs) are among the most prominent threats to the human population, our peace, and social stability. Therefore, their detection and quantification are of utmost importance to ensure the security and protection of mankind. In recent years, significant developments have been made in supramolecular chemistry, analytical chemistry, and molecular sensors, which have improved our capability to detect CWAs. Fluorescent and colorimetric chemosensors are attractive tools that allow the selective, sensitive, cheap, portable, and real-time analysis of the potential presence of CWAs, where suitable combinations of selective recognition and transduction can be integrated. In this review, we provide a detailed discussion on recently reported molecular sensors with a specific focus on the sensing of each class of CWAs such as nerve agents, blister agents, blood agents, and other toxicants. We will also discuss the current technology used by military forces, and these discussions will include the type of instrumentation and established protocols. Finally, we will conclude this review with our outlook on the limitations and challenges in the area and summarize the potential of promising avenues for this field.

Cucurbit[n]uril-based fluorescent indicator-displacement assays for sensing organic compounds

The widespread conversion of synthetic receptors into luminescent sensors has been achieved via the use of fluorescent-indicator displacement assays (F-IDAs). Due to their rigid structures and efficient binding affinities, cucurbit[n]urils, combined with a variety of fluorescent guests, have gained extensive utilization in fluorescent-indicator displacement assays for sensing non-fluorescent or weakly fluorescent organic compounds (analytes) in a selective and specific manner. This mini-review summarizes recent advances in the design of cucurbit[n]uril-based fluorescent-indicator displacement assays and discusses the current challenges and future prospects in this area.

Efficient discovery of potent α-glucosidase inhibitors from Paeoniae lactiflora using enzyme-MOF nanocomposites and competitive indicators

A great deal of attention has been paid to the seeds of Paeoniae lactiflora pall., an underutilized food resource, since its extract exhibits excellent α-glucosidase (GAA) inhibitory activity. In the present study, to gain further insight into this plant and find out potent GAA inhibitors, we established a novel ligand fishing strategy by introducing a competitive inhibitor as an indicator. After the successful establishment of this approach was verified by a series of methods, including kinetic assay, fluorescence determination, and HPLC, the newly developed ligand fishing method was applied to acquire potent GAA inhibitors from P. lactiflora seeds. Nine bioactive compounds were captured, and seven of them were identified as suffruticosol A, suffruticosol B, resveratrol, vitisin E, luteolin, trans-δ-viniferin, and ampelopsin E. The data of their GAA inhibitory activity demonstrated that these constituents were vigorously active against GAA with IC₅₀ values of 1.67-30.47 μM, while such value of 1-DNJ was 228.77 μM. Among them, vitisin E and ampelopsin E were reported to show such inhibitory activity for the first time. Collectively, our findings provide valuable clues for the further utilization of P. lactiflora seeds as a functional food, and offer a new avenue for acquiring potent inhibitors from natural resources.

Printed colorimetric chemosensor array on a 96-microwell paper substrate for metal ions in river water

Here, we propose a printed 96-well microtiter paper-based chemosensor array device (PCSAD) to simultaneously detect metal ions for river water assessment. Colorimetric chemosensors for metal ions have been designed based on molecular self-assembly using off-the-shelf catechol dyes and a phenylboronic acid (PBA) derivative. The colorimetric self-assembled chemosensors consisting of catechol dyes and a PBA derivative on a 96-well microtiter paper substrate demonstrated various color changes according to the disassembly of the ensembles by the addition of nine types of metal ions. An in-house-made algorithm was used to automate imaging analysis and extract color intensities at seven types of color channels from a captured digital image, allowing for rapid data processing. The obtained information-rich inset data showed fingerprint-like colorimetric responses and was applied to the qualitative and quantitative pattern recognition of metal ions using chemometric techniques. The feasibility of the 96-well microtiter PCSAD for environmental assessment has been revealed by the demonstration of a spike-and-recovery test against metal ions in a river water sample.

A Fluorescein-Substituted Perbrominated Dodecaborate Cluster as an Anchor Dye for Large Macrocyclic Hosts and Its Application in Indicator Displacement Assays

Perhalogenated boron clusters derived from B₁₂Br₁₂^2-, a superchaotropic dianion with a globular icosahedral shape, serve as inorganic cavity binders for cyclodextrins (CDs), in particular for large CDs (γ-CD and δ-CD), with high binding affinity (K_a > 10⁶ M^-1) in aqueous solution. This opens the door for applications of this anchoring moiety by linking it to organic residues, prominently fluorescent dyes. We report here the synthesis of a novel fluorescein-substituted perbrominated dodecaborate cluster by a copper(I)-catalyzed azide-alkyne click reaction. The formation of host-guest inclusion complexes between the dodecaborate-modified fluorescein dye and CDs can be readily followed by optical titrations, which afforded a binding constant of ∼1 × 10⁴ M^-1 with γ-CD; that is, the cluster functionalization allows binding of an otherwise nonbinding dye to the macrocycle ("anchor dye"). The formation of the 1:1 host-guest inclusion complex between the dye and γ-CD occurs over a broad range of pH values, which allows its application as a sensitive reporter pair according to the indicator displacement method, e.g., for drug detection. In addition, the substituted dye shows outer-wall binding to cucurbiturils through the dodecaborate moiety, leading to the formation of aggregates and significant fluorescence quenching of the dye.