Glycobiomimics and glycobiosensors

Advancing biological investigations using portable sensors for detection of sensitive samples

Portable biosensors are emerged as powerful diagnostic tools for analyzing intricately complex biological samples. These biosensors offer sensitive detection capabilities by utilizing biomolecules such as proteins, nucleic acids, microbes or microbial products, antibodies, and enzymes. Their speed, accuracy, stability, specificity, and low cost make them indispensable in forensic investigations and criminal cases. Notably, portable biosensors have been developed to rapidly detect toxins, poisons, body fluids, and explosives; they have proven invaluable in forensic examinations of suspected samples, generating efficient results that enable effective and fair trials. One of the key advantages of portable biosensors is their ability to provide sensitive and non-destructive detection of forensic samples without requiring extensive sample preparation, thereby reducing the possibility of false results. This comprehensive review provides an overview of the current advancements in portable biosensors for the detection of sensitive materials, highlighting their significance in advancing investigations and enhancing sensitive sample detection capabilities.

The long and successful journey of electrochemically active amino acids. From fundamental adsorption studies to potential surface engineering tools

Proteins have been the subject of electrochemical studies. It is possible to apply electrochemical techniques to obtain information about their structure due to the presence of five electroactive amino acids that can be oriented to the outside of the peptidic chain. These amino acids are L-Tryptophan (L-Trp), L-Tyrosine (L-Tyr), L-Histidine (L-His), L-Methionine (L-Met) and L-Cysteine (L-Cys); their electrochemical behavior being subject of extensive research, but it is still controversial. No spectroscopic investigations have been reported on L-Trp, and due to the short life time of the intermediates, ex situ techniques cannot be employed, leading to a never-ending discussion about possible intermediates. In the L-Tyr and L-His cases, spectroelectrochemical studies were performed and different intermediates were observed, suggesting that some intermediates may be observed under specific conditions, as proposed for L-Cys. This amino acid is the most interesting among the electroactive ones because of the presence of a thiol moiety at its side chain, leading to a wide range of oxidation states. It can adsorb onto surfaces of different crystallographic orientation in stereoselective conformation, modifying the surface for different applications.as a surface engineering tool since it plays the role of as an anchor for the growing of nanocrystals inside proteic templates.

An ultrasensitive impedimetric glycan biosensor with controlled glycan density for detection of lectins and influenza hemagglutinins

An impedimetric glycan biosensor with optimised glycan density was applied for the detection of lectins and influenza hemagglutinins down to attomolar concentrations (aM).

Highly sensitive fluorescence detection of glycoprotein based on energy transfer between CuInS2 QDs and rhodamine B

A highly sensitive fluorescence method for glycoprotein detection has been established based on fluorescence resonance energy transfer (FRET) between CuInS2 quantum dots (QDs) and rhodamine B (RB). Lectins comprise a group of proteins with unique affinities toward carbohydrate structures, so the process of FRET can occur between lectin-coated QDs (CuInS2 QDs-Con A conjugates, acceptors) and carbohydrate-coated RB (RB-NH2-glu conjugates, donors). The fluorescence of lectin-coated QDs was recovered in the presence of a glycoprotein such as glucose oxidase (GOx) and transferrin (TRF), which significantly reduced the FRET efficiency between the donor and the acceptor. Under optimal conditions, a linear correlation was established between the fluorescence intensity ratio I654/I577 and the TRF concentration over the range of 6.90 × 10(-10) to 3.45 × 10(-8) mol/L, with a detection limit of 2.5 × 10(-10) mol/L. The linear range for GOx is 3.35 × 10(-10) to 6.70 × 10(-8) mol/L, with a detection limit of 1.5 × 10(-10) mol/L. The proposed method was applied to the determination of glycoprotein in human serum and cell-extract samples with satisfactory results. Furthermore, CuInS2  QDs-Con A conjugates are used as safe and efficient optical nanoprobes in HepG2 cell imaging.

Perspectives in glycomics and lectin engineering

This chapter would like to provide a short survey of the most promising concepts applied recently in analysis of glycoproteins based on lectins. The first part describes the most exciting analytical approaches used in the field of glycoprofiling based on integration of nanoparticles, nanowires, nanotubes, or nanochannels or using novel transducing platforms allowing to detect very low levels of glycoproteins in a label-free mode of operation. The second part describes application of recombinant lectins containing several tags applied for oriented and ordered immobilization of lectins. Besides already established concepts of glycoprofiling several novel aspects, which we think will be taken into account for future, more robust glycan analysis, are described including modified lectins, peptide lectin aptamers, and DNA aptamers with lectin-like specificity introduced by modified nucleotides. The last part of the chapter describes a novel concept of a glycocodon, which can lead to a better understanding of glycan-lectin interaction and for design of novel lectins with unknown specificities and/or better affinities toward glycan target or for rational design of peptide lectin aptamers or DNA aptamers.

Are glycan biosensors an alternative to glycan microarrays?

Complex carbohydrates (glycans) play an important role in nature and study of their interaction with proteins or intact cells can be useful for understanding many physiological and pathological processes. Such interactions have been successfully interrogated in a highly parallel way using glycan microarrays, but this technique has some limitations. Thus, in recent years glycan biosensors in numerous progressive configurations have been developed offering distinct advantages compared to glycan microarrays. Thus, in this review advances achieved in the field of label-free glycan biosensors are discussed.

Nanoscale controlled architecture for development of ultrasensitive lectin biosensors applicable in glycomics

In this Minireview the most advanced patterning protocols and transducing schemes for development of ultrasensitive label-free and label-based lectin biosensors for glycoprofiling of disease markers and some cancerous cells are described. Performance of such lectin biosensors with interfacial properties tuned at a nanoscale are critically compared to the most sensitive immunoassay format of analysis and challenges ahead in the field are discussed. Moreover, key elements for future advances of such devices on the way to enhance robustness and practical applicability of lectin biosensors are revealed.

Construction and validation of a Sambucus nigra biosensor for cancer-associated STn antigen

A label-free electrochemical impedance spectroscopy biosensor for selective detection and discrimination of the cancer-associated sialyl-Tn (STn) antigen was developed by using Sambucus nigra agglutinin type I (SNA-I) as the recognition element. The SNA-I biosensor was constructed by immobilizing the lectin on screen-printed gold electrodes. The formation of a complex between SNA-I and STn-containing glycoproteins (transferrin and bovine submaxillary mucin) was monitored by measuring the impedance increase of the biosensor. The increase in electron transfer resistance was linearly proportional to the concentration of the glycoproteins up to 70 ng of transferrin and 40 ng of bovine submaxillary mucin, with a limit of detection of 20 ng for transferrin. Albumin, the most abundant serum protein, did not interfere in the detection of the STn-glycoproteins up to a concentration of 0.2 mg ml(-1). The developed lectin-based biosensor was used to evaluate the STn-expression in serum samples and discriminate samples from healthy individuals and patients with different types of malignant tumors, mostly carcinomas, where the increased expression of STn aberrant glycans is well established. This work demonstrates the feasibility of employing SNA-I to selectively recognize the STn epitope in glycoproteins and the use of the constructed biosensor was effective in the analysis of serum samples with the ability to discriminate in a fast way between cancer and healthy status. The proposed biosensor could be used for high-throughput, label-free profiling of the cancer-associated STn glycan expression in serum for diagnosis and therapy monitoring.

Surface glycosylation profiles of urine extracellular vesicles

Urinary extracellular vesicles (uEVs) are released by cells throughout the nephron and contain biomolecules from their cells of origin. Although uEV-associated proteins and RNA have been studied in detail, little information exists regarding uEV glycosylation characteristics. Surface glycosylation profiling by flow cytometry and lectin microarray was applied to uEVs enriched from urine of healthy adults by ultracentrifugation and centrifugal filtration. The carbohydrate specificity of lectin microarray profiles was confirmed by competitive sugar inhibition and carbohydrate-specific enzyme hydrolysis. Glycosylation profiles of uEVs and purified Tamm Horsfall protein were compared. In both flow cytometry and lectin microarray assays, uEVs demonstrated surface binding, at low to moderate intensities, of a broad range of lectins whether prepared by ultracentrifugation or centrifugal filtration. In general, ultracentrifugation-prepared uEVs demonstrated higher lectin binding intensities than centrifugal filtration-prepared uEVs consistent with lesser amounts of co-purified non-vesicular proteins. The surface glycosylation profiles of uEVs showed little inter-individual variation and were distinct from those of Tamm Horsfall protein, which bound a limited number of lectins. In a pilot study, lectin microarray was used to compare uEVs from individuals with autosomal dominant polycystic kidney disease to those of age-matched controls. The lectin microarray profiles of polycystic kidney disease and healthy uEVs showed differences in binding intensity of 6/43 lectins. Our results reveal a complex surface glycosylation profile of uEVs that is accessible to lectin-based analysis following multiple uEV enrichment techniques, is distinct from co-purified Tamm Horsfall protein and may demonstrate disease-specific modifications.

Ultrasensitive impedimetric lectin biosensors with efficient antifouling properties applied in glycoprofiling of human serum samples

Ultrasensitive impedimetric lectin biosensors recognizing different glycan entities on serum glycoproteins were constructed. Lectins were immobilized on a novel mixed self-assembled monolayer containing 11-mercaptoundecanoic acid for covalent immobilization of lectins and betaine terminated thiol to resist nonspecific interactions. Construction of biosensors based on Concanavalin A (Con A), Sambucus nigra agglutinin type I (SNA), and Ricinus communis agglutinin (RCA) on polycrystalline gold electrodes was optimized and characterized with a battery of tools including electrochemical impedance spectroscopy, various electrochemical techniques, quartz crystal microbalance (QCM), Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) and compared with a protein/lectin microarray. The lectin biosensors were able to detect glycoproteins from 1 fM (Con A), 10 fM (Ricinus communis agglutinin (RCA), or 100 fM (SNA) with a linear range spanning 6 (SNA), 7 (RCA), or 8 (Con A) orders of magnitude. Furthermore, a detection limit for the Con A biosensor down to 1 aM was achieved in a sandwich configuration. A nonspecific binding of proteins for the Con A biosensor was only 6.1% (probed with an oxidized invertase) of the signal toward its analyte invertase and a negligible nonspecific interaction of the Con A biosensor was observed in diluted human sera (1000×), as well. The performance of the lectin biosensors was finally tested by glycoprofiling of human serum samples from healthy individuals and those having rheumatoid arthritis, which resulted in a distinct glycan pattern between these two groups.

The sweet and sour of serological glycoprotein tumor biomarker quantification

Aberrant and dysregulated protein glycosylation is a well-established event in the process of oncogenesis and cancer progression. Years of study on the glycobiology of cancer have been focused on the development of clinically viable diagnostic applications of this knowledge. However, for a number of reasons, there has been only sparse and varied success. The causes of this range from technical to biological issues that arise when studying protein glycosylation and attempting to apply it to practical applications. This review focuses on the pitfalls, advances, and future directions to be taken in the development of clinically applicable quantitative assays using glycan moieties from serum-based proteins as analytes. Topics covered include the development and progress of applications of lectins, mass spectrometry, and other technologies towards this purpose. Slowly but surely, novel applications of established and development of new technologies will eventually provide us with the tools to reach the ultimate goal of quantification of the full scope of heterogeneity associated with the glycosylation of biomarker candidate glycoproteins in a clinically applicable fashion.

Electrochemical lectin based biosensors as a label-free tool in glycomics

Glycans and other saccharide moieties attached to proteins and lipids, or present on the surface of a cell, are actively involved in numerous physiological or pathological processes. Their structural flexibility (that is based on the formation of various kinds of linkages between saccharides) is making glycans superb "identity cards". In fact, glycans can form more "words" or "codes" (i.e., unique sequences) from the same number of "letters" (building blocks) than DNA or proteins. Glycans are physicochemically similar and it is not a trivial task to identify their sequence, or - even more challenging - to link a given glycan to a particular physiological or pathological process. Lectins can recognise differences in glycan compositions even in their bound state and therefore are most useful tools in the task to decipher the "glycocode". Thus, lectin-based biosensors working in a label-free mode can effectively complement the current weaponry of analytical tools in glycomics. This review gives an introduction into the area of glycomics and then focuses on the design, analytical performance, and practical utility of lectin-based electrochemical label-free biosensors for the detection of isolated glycoproteins or intact cells.

Tools from viruses: bacteriophage successes and beyond

Viruses are ubiquitous and can infect any of the three existing cellular lineages (Archaea, Bacteria and Eukarya). Despite the persisting negative public perception of these entities, scientists learnt how to domesticate some of them. The study of molecular mechanisms essential to the completion of viral cycles has greatly contributed to deciphering fundamental processes in biology. Nowadays, viruses have entered the biotechnological era and numerous applications have already been developed. Viral-derived tools are used to manipulate genetic information, detect, diagnose, control and cure infectious diseases, or even design new structural assemblies. With the recent advances in the field of metagenomics, an overwhelming amount of information on novel viruses has become available. As current tools have been historically developed from a limited number of viruses, the potential of discoveries from new archaeal, bacterial and eukaryotic viruses may be limited only by our understanding of the multiple facets of viral cycles.

Optical biosensors for food quality and safety assurance-a review

Food quality and safety is a scientific discipline describing handling, preparation and storage of food in ways that prevent food borne illness. Food serves as a growth medium for microorganisms that can be pathogenic or cause food spoilage. Therefore, it is imperative to have stringent laws and standards for the preparation, packaging and transportation of food. The conventional methods for detection of food contamination based on culturing, colony counting, chromatography and immunoassay are tedious and time consuming while biosensors have overcome some of these disadvantages. There is growing interest in biosensors due to high specificity, convenience and quick response. Optical biosensors show greater potential for the detection of pathogens, pesticide and drug residues, hygiene monitoring, heavy metals and other toxic substances in the food to check whether it is safe for consumption or not. This review focuses on optical biosensors, the recent developments in the associated instrumentation with emphasis on fiber optic and surface plasmon resonance (SPR) based biosensors for detecting a range of analytes in food samples, the major advantages and challenges associated with optical biosensors. It also briefly covers the different methods employed for the immobilization of bio-molecules used in developing biosensors.

Databases and tools in glycobiology

Glycans are crucial to the functioning of multicellular organisms. They may also play a role as mediators between host and parasite or symbiont. As many proteins (>50%) are posttranslationally modified by glycosylation, this mechanism is considered to be the most widespread posttranslational modification in eukaryotes. These surface modifications alter and regulate structure and biological activities/functions of proteins/biomolecules as they are largely involved in the recognition process of the appropriate structure in order to bind to the target cells. Consequently, the recognition of glycans on cellular surfaces plays a crucial role in the promotion or inhibition of various diseases and, therefore, glycosylation itself is considered to be a critical protein quality control attribute for commercial therapeutics, which is one of the fastest growing segments in the pharmaceutical industry. With the development of glycobiology as a separate discipline, a number of databases and tools became available in a similar way to other well-established "omics." Alleviating the recognized shortcomings of the available tools for data storage and retrieval is one of the highest priorities of the international glycoinformatics community. In the last decade, major efforts have been made, by leading scientific groups, towards the integration of a number of major databases and tools into a single portal, which would act as a centralized data repository for glycomics, equipped with a number of comprehensive analytical tools for data systematization, analysis, and comparison. This chapter provides an overview of the most important carbohydrate-related databases and glycoinformatic tools.

Structural glycobiology and human health

The glycans (carbohydrates) form a diverse group of biomolecules which play active parts in most physiological processes. The field of structural glycobiology concerns the structures of the glycans themselves, the proteins which interact with them and the nature of the interactions between the two. The resulting information is important for our understanding of human health and disease, and for development of new therapeutic strategies. A series of articles is introduced based on the topics covered at the Structural Glycobiology and Human Health Biochemical Society Focused Meeting. Their subjects range from in-depth determinations of three-dimensional protein structure to broad screening techniques for glycan-protein interactions relevant to disease processes, including bacterial, parasitic and viral infections, inflammatory processes, cancer and diabetes.

Recent Advances in Electrochemical Glycobiosensing

Biosensors based on electrochemical transduction mechanisms have recently made advances into the field of glycan analysis. These glyco-biosensors offer simple, rapid, sensitive, and economical approaches to the measurement need for rapid glycan analysis for biomarker detection, cancer and disease diagnostics, and bioprocess monitoring of therapeutic glycoproteins. Although the prevalent methods of glycan analysis (high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy) provide detailed identification and structural analysis of glycan species, there are significantly few low-cost, rapid glycan assays available for diagnostic and screening applications. Here we review instances in which glyco-biosensors have been used for glycan analysis using a variety of electrochemical transduction mechanisms (e.g., amperometric, potentiometric, impedimetric, and voltammetric), selective binding agents (e.g., lectins and antibodies), and redox species (e.g., enzyme substrates, inorganic, and nanomaterial).