Expanding the recognition of monosaccharides and glycans: A comprehensive analytical approach using chemical-nose/tongue technology and a comparison to lectin microarrays

Chemical-nose/tongue technologies are emerging as promising analytical tools for glycan analysis. After briefly introducing the importance of glycans and their analytical methods, including the lectin microarray (LMA) as one of the gold standards, the fundamental principles underlying chemical noses/tongues are explained and various applications for monosaccharides and glycans are introduced. Then, the similarities and differences of these two approaches are discussed. While both technologies aim to comprehensively profile biospecimens based on 'interaction patterns' between multiple recognition probes and analytes, each has its own strengths. LMAs excel at specific, targeted analysis based on defined lectin-glycan interactions, whereas chemical nose/tongue offers greater flexibility and expandability in terms of system design, making it well-suited for discovering unknown glycan profiles and detecting broader differences in glycan mixtures. In the future, chemical-nose/tongue technologies may be applied to niche areas in glycan analysis and become powerful tools that complement LMA techniques.

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.

Preparation of boronic acid and carboxyl-modified molecularly imprinted polymer and application in a novel chromatography mediated hollow fiber membrane to selectively extract glucose from cellulose hydrolysis

A novel boronic acid and carboxyl-modified glucose molecularly imprinted polymer (glucose-MIP) was prepared through suspension polymerization, which is based on 1.0 mmol glucose as a template, 1.2 mmol methacrylamidophenylboronic acid, and 6.8 mmol methacrylic acid as monomers, 19 mmol ethyleneglycol dimethacrylate, and 1 mmol methylene-bis-acrylamide as crosslinkers. The prepared glucose-MIP had a particle size of 25-70 μm, and was thermally stable below 215°C, with a specific surface area of 174.82 m^2. g^-1 and average pore size of 9.48 nm. The best selectivity between glucose and fructose was 2.71 and the maximum adsorption capacity of glucose-MIP was up to 236.32 mg^. g^-1 which was consistent with the Langmuir adsorption model. The similar adsorption abilities in 6 successive runs and the good desorption rate (99.4%) verified glucose-MIP could be reused. It was successfully used for extracting glucose from cellulose hydrolysis. The adsorption amount of glucose was 2.61 mg^. mL^-1 and selectivity between glucose and xylose reached 4.12. A newly established chromatography (glucose-MIP) mediated hollow fiber membrane method in time separated pure glucose from cellulose hydrolysates on a large-scale, and purified glucose solution with a concentration of 3.84 mg^. mL^-1 was obtained, which offered a feasible way for the industrial production of glucose from cellulose hydrolysates. This article is protected by copyright. All rights reserved.

Interactions between PAMAM-NH2 and 6-Mercaptopurine: Qualitative and Quantitative NMR studies

Despite being used as an anti-leukemic drug, the poor solubility of 6-mercaptopurine (6-MP) limits its use in topical and parenteral applications. Dendrimers are commonly used as drug carriers to improve their solubility in aqueous solution. In this work, the interactions between 6-MP and the amine-terminated poly(amidoamine) dendrimers (PAMAM-NH₂ ) were investigated by various NMR technology. The chemical shift titrations disclosed that the 6-MP interacted with the surface of PAMAM-NH₂ mainly through electrostatics. The determination of diffusion coefficient and relaxation measurements further confirmed the presence of interactions in 6-MP/PAMAM-NH₂ complexes. In addition, the encapsulation of 6-MP within the cavity of PAMAM-NH₂ was revealed through nuclear Overhauser effect spectroscopy and Saturation Transfer Double Difference analysis. Finally, the binding strength (H-8 is 100% and H-2 is 70%) of 6-MP to PAMAM-NH₂ was quantitatively expressed using epitope maps. This study provides a systematic methodology for qualitative and quantitative studies of the interactions between dendrimers and drug molecules in general.

Beta-Lactam Antibiotic Discrimination Using a Macromolecular Sensor in Water at Neutral pH

Penicillins and cephalosporins belong to the β-lactam antibiotic family, which accounts for more than half of the world market for antibiotics. Misuse of antibiotics harms human health and the environment. Here, we describe an easy, fast, and sensitive optical method for the sensing and discrimination of two penicillin and five cephalosporin antibiotics in buffered water at pH 7.4, using fifth-generation poly (amidoamine) (PAMAM) dendrimers and calcein, a commercially available macromolecular polyelectrolyte and a fluorescent dye, respectively. In aqueous solution at pH 7.4, the dendrimer and dye self-assemble to form a sensor that interacts with carboxylate-containing antibiotics through electrostatic interaction, monitored through changes in the dye’s spectroscopic properties. This response was captured through absorbance, fluorescence emission, and fluorescence anisotropy. The resulting data set was processed through linear discriminant analysis (LDA), a common pattern-base recognition method, for the differentiation of cephalosporins and penicillins. By pre-hydrolysis of the β-lactam rings under basic conditions, we were able to increase the charge density of the analytes, allowing us to discriminate the seven analytes at a concentration of 5 mM, with a limit of discrimination of 1 mM.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Molecular Boronic Acid-Based Saccharide Sensors

Boronic acids can reversibly bind diols, a molecular feature that is ubiquitous within saccharides, leading to their use in the design and implementation of sensors for numerous saccharide species. There is a growing understanding of the importance of saccharides in many biological processes and systems; while saccharide or carbohydrate sensing in medicine is most often associated with detection of glucose in diabetes patients, saccharides have proven to be relevant in a range of disease states. Herein the relevance of carbohydrate sensing for biomedical applications is explored, and this review seeks to outline how the complexity of saccharides presents a challenge for the development of selective sensors and describes efforts that have been made to understand the underpinning fluorescence and binding mechanisms of these systems, before outlining examples of how researchers have used this knowledge to develop ever more selective receptors.

Preparation of Boronic Acid-Functionalized Cryogels Using Modular and Clickable Building Blocks for Bacterial Separation

Composite cryogels containing boronic acid ligands are synthesized for effective separation and isolation of bacteria. The large and interconnected pores in cryogels enable fast binding and release of microbial cells. To control bacterial binding, an alkyne-tagged boronic acid ligand is conjugated to azide-functionalized cryogel via the Cu(I)-catalyzed azide-alkyne cycloaddition reaction. The boronic acid-functionalized cryogel binds Gram-positive and Gram-negative bacteria through reversible boronate ester bonds, which can be controlled by pH and simple monosaccharides. To increase the capacity of affinity separation, a new approach is used to couple the alkyne-tagged phenylboronic acid to cryogel via an intermediate polymer layer that provides multiple immobilization sites. The morphology and chemical composition of the composite cryogel are characterized systematically. The capability of the composite cryogel for the separation of Gram-positive and Gram-negative bacteria is investigated. The binding capacities of the composite cryogel for Escherichia coli and Staphylococcus epidermidis are 2.15 × 10⁹ and 3.36 × 10⁹ cfu/g, respectively. The bacterial binding of the composite cryogel can be controlled by adjusting pH. The results suggest that the composite cryogel may be used as affinity medium for rapid separation and isolation of bacteria from complex samples.

Pattern-Based Recognition Systems: Overcoming the Problem of Mixtures

The transformative potential of pattern-based sensing techniques is often hampered by their difficulty in dealing with mixtures of analytes, a drawback that severely limits the applications of this sensing approach (the "problem of mixtures"). We show here that this is not an intrinsic limitation of the pattern sensing method. Indeed, we developed general guidelines for the design of the sensing, signal detection, and data interpretation methods to avoid this constraint, which resulted in chemical fingerprinting systems capable of recognizing unknown mixtures of analytes in a single experiment, without separation or pre-treatment before data acquisition. In support of these design principles, we report their successful application to an important analytical problem, metal ion discrimination and quantitation, by constructing a sensor array that provided a linear colorimetric response over a wide range of analyte concentrations. The resulting data set was interpreted using common multivariate data processing algorithms to achieve quantitative identification and concentration determination for pure and mixture samples, with excellent predictive ability on unknowns. Separation and detection methods for analyte mixtures, normally envisioned as independent processes, were successfully integrated in a single system.

Supramolecular Sensor for Astringent Procyanidin C1: Fluorescent Artificial Tongue for Wine Components

An artificial tongue that detects astringent components for a comprehensive evaluation of taste has not been established to date. Herein, we first propose fluorescent polythiophene (PT) derivatives (S1-S3) modified with 3-pyridinium boronic acid as supramolecular chemosensors for wine components including astringent procyanidin C1. After numerous attempts for the synthetic conditions, more than 95 mol % of the PT unit was modified with the pyridinium boronic acid moiety. To evaluate the PT derivatives as chemosensors of the artificial tongue, qualitative and quantitative analyses were performed with four types of wine components (i.e., sweet, sour, bitter, and astringent tastes) in combination with pattern recognition models. Notably, procyanidin C1 in the actual wine sample was successfully detected in a quantitative manner. In other words, we have established an authentic artificial tongue using PT based supramolecular chemosensors.

Differential Sensing of Saccharides Based on an Array of Fluorinated Benzosiloxaborole Receptors

Fluorinated benzosiloxaboroles–silicon congeners of benzoxaboroles, were synthesized and tested as molecular receptors for mono- and disaccharides. The receptors differed in the Lewis acidity of the boron center as well as in the number of potential binding sites. The calculated stability constants indicated different binding affinity of benzosiloxaborole derivatives towards selected saccharides, enabling their classification using a receptor array-based sensing. Unique fluorescence fingerprints were created on the basis of competitive interactions of the studied receptors with both Alizarin Red S (ARS) and tested saccharide molecules. Detailed chemometric analysis of the obtained fluorescence data (based on partial least squares-discriminant analysis and hierarchical clustering analysis) provided the differential sensing of common saccharides, in particular the differentiation between glucose and fructose. In addition, DFT calculations were carried out to shed light on the binding mechanism under different pH conditions.

Disposable paper strips for carboxylate discrimination

A fluorescent macromolecular chemosensor, built from readily available components, performs chemical fingerprinting of carboxylate anions on low-cost, disposable paper supports.

Low-Temperature Thermopower in CoSbS

We report on giant thermopower of S=2.5  mV/K in CoSbS single crystals: a material that shows strong high-temperature thermoelectric performance when doped with Ni or Se. Changes of low-temperature thermopower induced by a magnetic field point to the mechanism of electronic diffusion of carriers in the heavy valence band. Intrinsic magnetic susceptibility is consistent with the Kondo-insulatorlike accumulation of electronic states around the gap edges. This suggests that giant thermopower stems from temperature-dependent renormalization of the noninteracting bands and buildup of the electronic correlations on cooling.

Array-based Generation of Response Patterns with Common Fluorescent Dyes for Identification of Proteins and Cells

A differential array consisting of commercially available common fluorescent dyes was constructed for the identification of proteins and human cancer cells. Fluorescence of dyes was differently altered by mixing with proteins and human cancer cells, generating response patterns that are unique to the analytes. Linear discriminant analysis of the obtained patterns enabled the accurate identification of eight proteins and three human cancer cells. As this system can be easily prepared, it would offer a unique opportunity for array-based differential biosensing.

Voltammetric Response of Alizarin Red S-Confined Film-Coated Electrodes to Diol and Polyol Compounds: Use of Phenylboronic Acid-Modified Poly(ethyleneimine) as Film Component

Alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of phenylboronic acid-modified poly(ethyleneimine) (PBA-PEI) and carboxymethylcellulose (CMC) to study the voltammetric response to diol and polyol compounds. The LbL film-coated gold (Au) electrode and quartz slide were immersed in an ARS solution to uptake ARS into the film. UV-visible absorption spectra of ARS-confined LbL film suggested that ARS formed boronate ester (ARS-PBS) in the film. The cyclic voltammetry of the ARS-confined LbL film-coated electrodes exhibited oxidation peaks at -0.50 and -0.62 V, which were ascribed to the oxidation reactions of ARS-PBS and free ARS, respectively, in the LbL film. The peak current at -0.62 V increased upon the addition of diol or polyol compounds such as L-dopa, glucose, and sorbitol into the solution, depending on the concentration, whereas the peak current at -0.50 V decreased. The results suggest a possible use of ARS-confined PBA-PEI/CMC LbL film-coated Au electrodes for the construction of voltammetric sensors for diol and polyol compounds.

Hyper-Cross-Linked Polypyrene Spheres Functionalized with 3-Aminophenylboronic Acid for the Electrochemical Detection of Diols

A sensor for the determination of diols using 3-aminophenylboronic acid (APBA)-functionalized hyper-cross-linked polypyrene (PPy) (APBA@PPy) is presented. The uniform (∼1 μm in diameter) and highly porous (628 m2 g-1 in specific surface area) PPy spheres are fabricated via a one-pot protocol that consists of ZnBr2-catalyzed alkylation of pyrene, a subsequent cross-linking reaction, and concomitant self-assembly. The PPy spheres formed within a few minutes at mild conditions are featured by an excellent structural integrity and inertness to organic solvents. Thus, the APBA@PPy composites (∼1 μm in diameter; 458 m2 g-1 in specific surface area) are prepared simply by substituting unreacted bromomethyl groups on the surface of PPy spheres for APBA. The APBA@PPy composites are successfully applied for the electrochemical sensing of d-glucose and dopamine. A dye displacement assay is also performed using alizarin red dye conjugated to boronic acid in glucose buffer solution.

Alizarin Red S-Confined Layer-By-Layer Films as Redox-Active Coatings on Electrodes for the Voltammetric Determination of L-Dopa

The preparation of redox-active coatings is a key step in fabricating electrochemical biosensors. To this goal, a variety of coating materials have been used in combination with redox-active compounds. In this study, alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of poly(ethyleneimine) (PEI) and carboxymethylcellulose (CMC) to study the redox properties. A gold (Au) disc electrode coated with PEI/CMC LbL film was immersed in an ARS solution to uptake ARS into the film. ARS was successfully confined in the LbL film through electrostatic interactions. The cyclic voltammogram (CV) of ARS-confined PEI/CMC film-coated electrodes thus prepared exhibited redox waves in the potential range from -0.5 to -0.7 V originating from 9,10-anthraquinone moiety in ARS, demonstrating that ARS preserves its redox activity in the LbL film. An additional oxidation peak appeared around -0.4 V in the CV recorded in the solution containing phenylboronic acid (PBA), due to the formation of a boronate ester of ARS (ARS-PBA) in the film. The oxidation peak current at -0.4 V decreased upon addition of 3,4-dihydroxyphenylalanine (L-dopa) to the solution. Thus, the results suggest a potential use of the ARS-confined PEI/CMC films for constructing voltammetric sensors for L-dopa.