Exploring glycans as vital biological macromolecules: A comprehensive review of advancements in biomedical frontiers

This comprehensive review delves into the intricate landscape of glycans and glycoconjugates, unraveling their multifaceted roles across diverse biological dimensions. From influencing fundamental cellular processes such as signaling, recognition, and adhesion to exerting profound effects at the molecular and genetic levels, these complex carbohydrate structures emerge as linchpins in cellular functions and interactions. The structural diversity of glycoconjugates, which can be specifically classified into glycoproteins, glycolipids, and proteoglycans, underscores their importance in shaping the architecture of cells. Beyond their structural roles, these molecules also play key functions in facilitating cellular communication and modulating recognition mechanisms. Further, glycans and glycoconjugates prove invaluable as biomarkers in disease diagnostics, particularly in cancer, where aberrant glycosylation patterns offer critical diagnostic cues. Furthermore, the review explores their promising therapeutic applications, ranging from the development of glycan-based nanomaterials for precise drug delivery to innovative interventions in cancer treatment. This review endeavors to comprehensively explore the intricate functions of glycans and glycoconjugates, with the primary goal of offering valuable insights into their extensive implications in both health and disease. Encompassing a broad spectrum of biological processes, the focus of the review aims to provide a comprehensive understanding of the significant roles played by glycans and glycoconjugates.

Evolution of a Reagent-Controlled Strategy for β-Selective C-Glycoside Synthesis

C-alkyl glycosides represent an attractive class of non-hydrolyzable carbohydrate mimetics which possess enormous potential as next-generation therapeutics. Methods for the direct stereoselective synthesis of C-alkyl glycosides with a broad substrate tolerance are limited, however. This is especially in the case of β-linked C-alkyl glycosides, where direct methods for synthesis from commonly available coupling partners remain limited. This account describes the evolution of our laboratory’s studies on glycosyl sulfonate chemistry from a method for the construction of simple β-linked 2-deoxy-sugars to a technology for the direct synthesis of β-linked acyl and homoacyl glycosides that can be elaborated into more complex structures.

Surface plasmon resonance study for a reliable determination of the affinity constant of multivalent grafted beads

In this study, galactose-grafted beads were prepared using the main design principle of the cluster effect. Galactose was chosen as the sugar for investigation because it acts as the main building block of long glycan chains and because a simple and fast protocol is still required for its immobilization. For the analysis, the lectin, ligand of the galactose, was immobilized on a gold plasmonic substrate. After preliminary characterization of the galactose-grafted beads, the investigation of the surface plasmon surface behavior of the system was carried out, for studying the affinity constant of the multivalent beads. The results of steady-state and of the kinetics analysis evidenced a higher affinity of the galactose-grafted beads over the beadless galactose solution. For the association kinetics analysis, a Langmuir isotherm was applied to the data. The analysis of the rate of dissociation evidenced the most important differences between the two samples, based on the more difficult release of the galactose-grafted beads during washing. To confirm the influence of the glycoside cluster effect, a low-density lectin substrate was tested, and the results evidenced that the characteristic size of the molecules determines a threshold for the cluster density. The calculated detection limit and dissociation constants were 3.5 μM and 40.2 μM, respectively. Considering those results, the evaluation of the affinities toward the receptors depends on the cluster density and then, it should be designed for mimicking the biological samples.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

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.

A Reusable Column Method Using Glycopolymer-Functionalized Resins for Capture-Detection of Proteins and Escherichia coli

The use of glycopolymer-functionalized resins (Resin-Glc), as a solid support, in column mode for bacterial/protein capture and quantification is explored. The Resin-Glc is synthesized from commercially available chloromethylated polystyrene resin and glycopolymer, and is characterized by fourier transform infrared spectroscopy, thermogravimetry, and elemental analysis. The percentage of glycopolymer functionalized on Resin-Glc is accounted to be 5 wt%. The ability of Resin-Glc to selectively capture lectin, Concanavalin A, over Peanut Agglutinin, reversibly, is demonstrated for six cycles of experiments. The bacterial sequestration study using SYBR (Synergy Brands, Inc.) Green I tagged Escherichia coli/Staphylococcus aureus reveals the ability of Resin-Glc to selectively capture E. coli over S. aureus. The quantification of captured cells in the column is carried out by enzymatic colorimetric assay using methylumbelliferyl glucuronide as the substrate. The E. coli capture studies reveal a consistent capture efficiency of 10⁵  CFU (Colony Forming Units) g^-1 over six cycles. Studies with spiked tap water samples show satisfactory results for E. coli cell densities ranging from 10² to 10⁷  CFU mL^-1 . The method portrayed can serve as a basis for the development of a reusable solid support in capture and detection of proteins and bacteria.

Development of Diagnostic Tests for Detection of SARS-CoV-2

One of the most effective ways to prevent the spread of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is to develop accurate and rapid diagnostic tests. There are a number of molecular, serological, and imaging methods that are used to diagnose this infection in hospitals and clinical settings. The purpose of this review paper is to present the available approaches for detecting SARS-CoV-2 and address the advantages and limitations of each detection method. This work includes studies from recent literature publications along with information from the manufacturer's manuals of commercially available SARS-CoV-2 diagnostic products. Furthermore, supplementary information from the Food & Drug Administration (FDA), Centers for Disease Control and Prevention (CDC), and World Health Organization (WHO) is cited. The viral components targeted for virus detection, the principles of each diagnostic technique, and the detection efficiency of each approach are discussed. The potential of using diagnostic tests that were originally developed for previous epidemic viruses is also presented.

Synthetic Glycobiology: Parts, Systems, and Applications

Protein glycosylation, the attachment of sugars to amino acid side chains, can endow proteins with a wide variety of properties of great interest to the engineering biology community. However, natural glycosylation systems are limited in the diversity of glycoproteins they can synthesize, the scale at which they can be harnessed for biotechnology, and the homogeneity of glycoprotein structures they can produce. Here we provide an overview of the emerging field of synthetic glycobiology, the application of synthetic biology tools and design principles to better understand and engineer glycosylation. Specifically, we focus on how the biosynthetic and analytical tools of synthetic biology have been used to redesign glycosylation systems to obtain defined glycosylation structures on proteins for diverse applications in medicine, materials, and diagnostics. We review the key biological parts available to synthetic biologists interested in engineering glycoproteins to solve compelling problems in glycoscience, describe recent efforts to construct synthetic glycoprotein synthesis systems, and outline exemplary applications as well as new opportunities in this emerging space.

A Graphene-Based Glycan Biosensor for Electrochemical Label-Free Detection of a Tumor-Associated Antibody

The study describes development of a glycan biosensor for detection of a tumor-associated antibody. The glycan biosensor is built on an electrochemically activated/oxidized graphene screen-printed electrode (GSPE). Oxygen functionalities were subsequently applied for covalent immobilization of human serum albumin (HSA) as a natural nanoscaffold for covalent immobilization of Thomsen-nouvelle (Tn) antigen (GalNAc-O-Ser/Thr) to be fully available for affinity interaction with its analyte-a tumor-associated antibody. The step by step building process of glycan biosensor development was comprehensively characterized using a battery of techniques (scanning electron microscopy, atomic force microscopy, contact angle measurements, secondary ion mass spectrometry, surface plasmon resonance, Raman and energy-dispersive X-ray spectroscopy). Results suggest that electrochemical oxidation of graphene SPE preferentially oxidizes only the surface of graphene flakes within the graphene SPE. Optimization studies revealed the following optimal parameters: activation potential of +1.5 V vs. Ag/AgCl/3 M KCl, activation time of 60 s and concentration of HSA of 0.1 g L^-1. Finally, the glycan biosensor was built up able to selectively and sensitively detect its analyte down to low aM concentration. The binding preference of the glycan biosensor was in an agreement with independent surface plasmon resonance analysis.

Direct immobilization of sugar probes on bovine serum albumin-coated gold substrate for the development of glycan biosensors

Glycan biosensors based on surface plasmon resonance (SPR) spectroscopy have attracted a great deal of interest due to their potential applications in numerous biological and biomedical fields. Controlled immobilization of sugar probes on a gold substrate is believed to be critical for the performance of these SPR biosensors. In this regard, herein the authors report a direct coupling of mannose probes with bovine serum albumin (BSA) layer on the gold substrate via a squaric acid-mediated reaction under mild conditions, in which the BSA layer provides not only reactive amine groups but also a nonfouling surface property. SPR measurements show that the resultant biosensor with an appropriate amount of mannose probes exhibits high affinity to its corresponding lectin (i.e., concanavalin A) and at the same time could resist nonspecific adsorption of other lectins. The limit of detection of the current SPR biosensor is 1.9 nM. Thus, the squaric acid-mediated immobilization strategy appears to be effective and useful for the fabrication of bioanalytical devices.

Aptamer-recognized carbohydrates on the cell membrane revealed by super-resolution microscopy

Carbohydrates are one of the most important components on the cell membrane, which participate in various physiological activities, and their aberrant expression is a consequence of pathological changes. In previous studies, carbohydrate analysis basically relied on lectins. However, discrimination between lectins still exists due to their multivalent character. Furthermore, the structures obtained by carbohydrate-lectin crosslinking confuse our direct observation to some extent. Fortunately, the emergence of aptamers, which are smaller and more flexible, has provided us an unprecedented choice. Herein, an aptamer recognition method with high precise localization was developed for imaging membrane-bound N-acetylgalactosamine (GalNAc). By using direct stochastic optical reconstruction microscopy (dSTORM), we compared this aptamer recognition method with the lectin recognition method for visualizing the detailed structure of GalNAc at the nanometer scale. The results indicated that GalNAc forms irregular clusters on the cell membrane with a resolution of 23 ± 7 nm by aptamer recognition. Additionally, when treated with N-acetylgalactosidase, the aptamer-recognized GalNAc shows a more significant decrease in cluster size and localization density, thus verifying better specificity of aptamers than lectins. Collectively, our study suggests that aptamers can act as perfect substitutes for lectins in carbohydrate labeling, which will be of great potential value in the field of super-resolution fluorescence imaging.

Responsive Photonic Crystal Carbohydrate Hydrogel Sensor Materials for Selective and Sensitive Lectin Protein Detection

Lectin proteins, such as the highly toxic lectin protein, ricin, and the immunochemically important lectin, jacalin, play significant roles in many biological functions. It is highly desirable to develop a simple but efficient method to selectively detect lectin proteins. Here we report the development of carbohydrate containing responsive hydrogel sensing materials for the selective detection of lectin proteins. The copolymerization of a vinyl linked carbohydrate monomer with acrylamide and acrylic acid forms a carbohydrate hydrogel that shows specific "multivalent" binding to lectin proteins. The resulting carbohydrate hydrogels are attached to 2-D photonic crystals (PCs) that brightly diffract visible light. This diffraction provides an optical readout that sensitively monitors the hydrogel volume. We utilize lactose, galactose, and mannose containing hydrogels to fabricate a series of 2-D PC sensors that show strong selective binding to the lectin proteins ricin, jacalin, and concanavalin A (Con A). This binding causes a carbohydrate hydrogel shrinkage which significantly shifts the diffraction wavelength. The resulting 2-D PC sensors can selectively detect the lectin proteins ricin, jacalin, and Con A. These unoptimized 2-D PC hydrogel sensors show a limit of detection (LoD) of 7.5 × 10^-8 M for ricin, a LoD of 2.3 × 10^-7 M for jacalin, and a LoD of 3.8 × 10^-8 M for Con A, respectively. This sensor fabrication approach may enable numerous sensors for the selective detection of numerous lectin proteins.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

BSA-Sugar Conjugates as Ideal Building Blocks for SPR-Based Glycan Biosensors

Controlled immobilization of sugar probes is of key importance for the development of glycan biosensors. To this end, a series of BSA-sugar conjugates with different numbers of mannose units are prepared via the squaric acid-mediated coupling reaction. The conjugates can absorb directly on gold substrate without any derivation reactions, thus providing a simple and effective method for the construction of SPR-based glycan biosensors. SPR measurements show that the BSA-mannose conjugate with 11 mannoses exhibit the highest affinity to the lectin concanavalin A with a limit of detection of ca. 1.8 nM. Regeneration and specificity of the obtained glycan biosensors are also investigated.

A reusable supramolecular platform for the specific capture and release of proteins and bacteria

A re-usable supramolecular platform with the capability of high-efficiency capture and on-demand release of specific proteins and bacteria was developed.

Improved workflow for the efficient preparation of ready to use CMP-activated sialic acids

Natural and synthetically modified cytidine monophosphate activated sialic acids (CMP-Sias) are essential research assets in the field of glycobiology: among other applications, they can be used to probe glycans, detect sialylation defects at the cell surface or carry out detailed studies of sialyltransferase activities. However, these chemical tools are notoriously unstable because of hydrolytic decomposition, and are very time-consuming and costly to obtain. They are nigh impossible to store with satisfactory purity, and their preparation requires multiple laborious purification steps that usually lead to heavy product loss. Using in situ time-resolved ³¹P phosphorus nuclear magnetic resonance (³¹P NMR), we precisely established the kinetics of formation and degradation of a number of CMP-Sias including CMP-Neu5Ac, CMP-Neu5Gc, CMP-SiaNAl and CMP-SiaNAz in several experimental conditions. ³¹P NMR can be carried out in undeuterated solvents and is a sensitive and nondestructive technique that allows for direct in situ monitoring and optimization of chemo-enzymatic syntheses that involve phosphorus-containing species. Thus, we showed that CMP-sialic acid derivatives can be robustly obtained in high yields using the readily available Neisseria meningitidis CMP-sialic acid synthase. This integrated workflow takes less than an hour, and the freshly prepared CMP-Sias can be directly transferred to sialylation biological assays without any purification step.