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

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.

A brief account of evolution of assays to study carbohydrate-protein interaction

Molecular recognition remains one of the most desirable means of cellular communication. Each cell offers a unique surface pattern of biomolecules that makes it very specific about the nature of molecules that interact with the cell. Protein-glycan interaction has been one of the most common forms of cell signaling. Glycans expressed on the cell surface interact with an exogenous protein, and in many cases lead to a physiological response. These carbohydrate-binding proteins, commonly known as lectins, are very specific to the glycan they bind to. An exogenous lectin interacting with an animal cell surface glycan is generally studied using the classical hemagglutination assay. However, this method presents certain challenges that make it imperative to design and develop novel methods that are more specific and efficient in their interaction. In the last decade, a few methods have been developed to analyze more diverse reactions and use a lesser amount of sample. In some cases, the processing of the sample is also reduced. This review discusses how the methods have evolved over the decades and how they have reduced error while becoming more efficient.

Aberrant protein glycosylation: Implications on diagnosis and Immunotherapy

Glycosylation-mediated post-translational modification is critical for regulating many fundamental processes like cell division, differentiation, immune response, and cell-to-cell interaction. Alterations in the N-linked or O-linked glycosylation pattern of regulatory proteins like transcription factors or cellular receptors lead to many diseases, including cancer. These alterations give rise to micro- and macro-heterogeneity in tumor cells. Here, we review the role of O- and N-linked glycosylation and its regulatory function in autoimmunity and aberrant glycosylation in cancer. The change in cellular glycome could result from a change in the expression of glycosidases or glycosyltransferases like N-acetyl-glucosaminyl transferase V, FUT8, ST6Gal-I, DPAGT1, etc., impact the glycosylation of target proteins leading to transformation. Moreover, the mutations in glycogenes affect glycosylation patterns on immune cells leading to other related manifestations like pro- or anti-inflammatory effects. In recent years, understanding the glycome to cancer indicates that it can be utilized for both diagnosis/prognosis as well as immunotherapy. Studies involving mass spectrometry of proteome, site- and structure-specific glycoproteomics, or transcriptomics/genomics of patient samples and cancer models revealed the importance of glycosylation homeostasis in cancer biology. The development of emerging technologies, such as the lectin microarray, has facilitated research on the structure and function of glycans and glycosylation. Newly developed devices allow for high-throughput, high-speed, and precise research on aberrant glycosylation. This paper also discusses emerging technologies and clinical applications of glycosylation.

Glycan-Based Electrochemical Biosensors: Promising Tools for the Detection of Infectious Diseases and Cancer Biomarkers

Glycan-based electrochemical biosensors are emerging as analytical tools for determining multiple molecular targets relevant to diagnosing infectious diseases and detecting cancer biomarkers. These biosensors allow for the detection of target analytes at ultra-low concentrations, which is mandatory for early disease diagnosis. Nanostructure-decorated platforms have been demonstrated to enhance the analytical performance of electrochemical biosensors. In addition, glycans anchored to electrode platforms as bioreceptors exhibit high specificity toward biomarker detection. Both attributes offer a synergy that allows ultrasensitive detection of molecular targets of clinical interest. In this context, we review recent advances in electrochemical glycobiosensors for detecting infectious diseases and cancer biomarkers focused on colorectal cancer. We also describe general aspects of structural glycobiology, definitions, and classification of electrochemical biosensors and discuss relevant works on electrochemical glycobiosensors in the last ten years. Finally, we summarize the advances in electrochemical glycobiosensors and comment on some challenges and limitations needed to advance toward real clinical applications of these devices.

Progress toward rapid, at-line N-glycosylation detection and control for recombinant protein expression

Proteins continue to represent a large fraction of the therapeutics market, reaching over a hundred billion dollars in market size globally. One key feature of protein modification that can affect both structure and function is the addition of glycosylation following protein folding, leading to regulatory requirements for the accurate assessment of protein attributes, including glycan structures. The non-template-driven, innately heterogeneous N-glycosylation process thus requires accurate detection to robustly generate protein therapies. A challenge exists in the timely detection of protein glycosylation without labor-intensive manipulation. In this article, we discuss progress toward N-glycoprotein control, focusing on novel control strategies and the advancement of rapid, high-throughput analysis methods.

Advances in analysis of pharmaceuticals by using graphene-based sensors

Safe and effective use of drugs relies on proper pharmaceutical analysis. Graphene has been extensively used to construct sensors for this purpose. Over the years, a large variety of pharmaceutical sensors have been developed from graphene or its derivatives. This articles reviews the current status of sensor development from graphene and its derivatives, and discusses the use of graphene-based sensors in pharmaceutical analysis. It is hoped that this article cannot only offer a snapshot of recent advances in the fabrication and use of graphene-based sensors, but can also provide insights into future engineering and optimization of the sensors for effective pharmaceutical analysis.

Applications of graphene-based electrochemical and optical biosensors in early detection of cancer biomarkers

Graphene is a one-atom-thick carbon compound, which holds promises for detecting cancer biomarkers along with its derivatives. The atom-wide graphene layer is ideal for cancer biomarker detection due to its unique physicochemical properties like increased electrical and thermal conductivity, optical transparency, and enhanced chemical and mechanical strength. The scientific aim of any biosensor is to create a smaller and portable point of care device for easy and early cancer detection; graphene is able to live up to that. Apart from tumour detection, graphene-based biosensors can diagnose many diseases, their biomarkers, and pathogens. Many existing remarkable pieces of research have proven the candidacy of nanoparticles in most cancer biomarkers detection. This article discusses the effectiveness of graphene-based biosensors in different cancer biomarker detection. This article provides a detailed review of graphene and its derivatives that can be used to detect cancer biomarkers with high specificity, sensitivity, and selectivity. We have highlighted the synthesis procedures of graphene and its products and also discussed their significant properties. Furthermore, we provided a detailed overview of the recent studies on cancer biomarker detection using graphene-based biosensors. The different paths to create and modify graphene surfaces for sensory applications have also been highlighted in each section. Finally, we concluded the review by discussing the existing challenges of these biosensors and also highlighted the steps that can be taken to overcome them.

Review of Detection and Quantification of Rabies Virus Antibodies

Rabies is an almost invariably fatal disease. According to the World Health Organization (WHO), rabies virus neutralizing antibody (RVNA) titers of ≥0.5 IU/mL are considered adequate for rabies protection. Therefore, detection and quantification of RABV antibodies are important. Many methods have been developed for detecting RABV antibodies. In the present study, we reviewed several methods of detecting RABV antibodies in human and animal samples and evaluated and compared their performance. Of 34 methods, 5 demonstrated unsatisfactory sensitivity or specificity. The others exhibited sensitivity and specificity of ≥75%. The correlation coefficient for five of eight methods was >0.8. The Bland-Altman mean bias of five of five methods was <±2.0. The kappa values of 25 of 28 methods were higher than 0.4, demonstrating at least moderate agreement. Analysis of the performance of these methods emphasized that any new technology should be considered carefully and objectively before being used as an appropriate and applicable alternative.

Novel Trends in Electrochemical Biosensors for Early Diagnosis of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a multifactorial progressive and irreversible neurodegenerative disorder affecting mainly the population over 65 years of age. It is becoming a global health and socioeconomic problem, and the current number of patients reaching 30-50 million people will be three times higher over the next thirty years.

OBJECTIVE

Late diagnosis caused by decades of the asymptomatic phase and invasive and cost-demanding diagnosis are problems that make the whole situation worse. Electrochemical biosensors could be the right tool for less invasive and inexpensive early diagnosis helping to reduce spend sources- both money and time.

METHOD

This review is a survey of the latest advances in the design of electrochemical biosensors for the early diagnosis of Alzheimer's disease. Biosensors are divided according to target biomarkers.

CONCLUSION

Standard laboratory methodology could be improved by analyzing a combination of currently estimated markers along with neurotransmitters and genetic markers from blood samples, which make the test for AD diagnosis available to the wide public.

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.

Advances in antibody nanoconjugates for diagnosis and therapy: A review of recent studies and trends

Nowadays, the targeted imaging probe and drug delivery systems are the novel breakthrough area in the nanomedicine and treatment of various diseases. Conjugation of monoclonal antibodies and their fragments on nanoparticles (NPs) have a remarkable impact on personalized medicine, such that it provides specific internalization and accumulation in the tumor microenvironment. Targeted imaging and early detection of cancer is presumably the strong participant to a diminution in mortality and recurrence of cancer disease that will be the next generation of the imaging device in clinical application. These intelligent delivery systems can deliver therapeutic agents that target cancerous tissue with minimal side effects and a wide therapeutic window. Overall, the linkage between the antibody and NPs is a critical subject and requires precise design and development. The attachment of antibody nanoconjugates (Ab-NCs) on the antigen surface shouldn't affect the function of the antibody-antigen binding. Also, the stability of the antibody nanoconjugates in blood circulation is concerned to avoid the release of drug in non-targeted regions and the possible for specific toxicity while disposal to the desired site. Here, we update the recent progress of Ab-NCs to improve early detection and cancer therapy.

Reversible Lectin Binding to Glycan-Functionalized Graphene

The monolayer character of two-dimensional materials predestines them for application as active layers of sensors. However, their inherent high sensitivity is always accompanied by a low selectivity. Chemical functionalization of two-dimensional materials has emerged as a promising way to overcome the selectivity issues. Here, we demonstrate efficient graphene functionalization with carbohydrate ligands—chitooligomers, which bind proteins of the lectin family with high selectivity. Successful grafting of a chitooligomer library was thoroughly characterized, and glycan binding to wheat germ agglutinin was studied by a series of methods. The results demonstrate that the protein quaternary structure remains intact after binding to the functionalized graphene, and that the lectin can be liberated from the surface by the addition of a binding competitor. The chemoenzymatic assay with a horseradish peroxidase conjugate also confirmed the intact catalytic properties of the enzyme. The present approach thus paves the way towards graphene-based sensors for carbohydrate–lectin binding.

Glycan Nanobiosensors

This review paper comprehensively summarizes advances made in the design of glycan nanobiosensors using diverse forms of nanomaterials. In particular, the paper covers the application of gold nanoparticles, quantum dots, magnetic nanoparticles, carbon nanoparticles, hybrid types of nanoparticles, proteins as nanoscaffolds and various nanoscale-based approaches to designing such nanoscale probes. The article covers innovative immobilization strategies for the conjugation of glycans on nanoparticles. Summaries of the detection schemes applied, the analytes detected and the key operational characteristics of such nanobiosensors are provided in the form of tables for each particular type of nanomaterial.

Formation of a Photoelectrochemical Z-Scheme Structure with Inorganic/Organic Hybrid Materials for Evaluation of Receptor Protein Expression on the Membrane of Cancer Cells

Quantitative analysis of receptor protein expression is essential to give new insights into tumor-related research. Benefitting from their high sensitivity and low background, photoelectrochemical (PEC) platforms are considered as powerful tools for evaluating the expression of receptor proteins. Herein, to reduce the cytotoxicity and facilitate the subsequent assembly, l-cysteine-modified Ag-ZnIn₂S₄ quantum dots (l-Cys AZIS QDs) are prepared and PEC responses under the irradiation of long wavelength light are obtained. To further improve the PEC behavior, iron phthalocyanine (FePc) is employed to form a Z-scheme structure with l-Cys AZIS QDs. The Z-scheme structure based on l-Cys AZIS QDs/FePc hybrid materials exhibits high photo-to-electric conversion efficiency and can be excited with near-infrared range light. Because hyaluronic acid linked to photoactive materials can recognize CD44 expressed on the membrane of cancer cells, cancer cells are immobilized onto l-Cys AZIS QDs/FePc hybrid materials, inducing a decrease of the photocurrent intensity. Consequently, a PEC cytosensor is constructed to quantify cancer cells expressing CD44. The PEC analytical platform is able to determine A549 cells in the range of 2 × 10² to 4.5 × 10⁶ cells/mL, and a detection limit of 15 cells/mL is realized in the case of S/N = 3. In addition, the expression of CD44 in A549 and other five cancer cells is measured with this PEC method. Depending on our data, the expression of CD44 in different cancer cells is distinct, indicating great potential of this method in receptor protein-related studies.

Applications of Graphene-Based Materials in Sensors

This Special Issue compiles a set of innovative developments on the use of graphene-based materials in the fabrication of sensors. In particular, these contributions report original studies on a wide variety of sensors, such as gas sensors for NO₂ or NH₃ detection, antibody biosensors or mass sensors. All these devices have one point in common: they have been built using graphene-based materials like graphene, graphene oxide, reduced graphene oxide, inkject printing graphene, graphene-based composite sponges, graphene screen-printed electrodes or graphene quantum dots.