Sub 2-μm macroporous silica particles derivatized for enhanced lectin affinity enrichment of glycoproteins

Classification of Extracellular Vesicles Based on Surface Glycan Structures by Spongy-like Separation Media

Extracellular vesicles (EVs) are lipid bilayer vesicles that enclose various biomolecules. EVs hold promise as sensitive biomarkers to detect and monitor various diseases. However, they have heterogeneous molecular compositions. The compositions of EVs from identical donor cells obtained using the same purification methods may differ, which is a significant obstacle for elucidating objective biological functions. Herein, the potential of a novel lectin-based affinity chromatography (LAC) method to classify EVs based on their glycan structures is demonstrated. The proposed method utilizes a spongy-like monolithic polymer (spongy monolith, SPM), which consists of poly(ethylene-co-glycidyl methacrylate) with continuous micropores and allows an efficient in situ protein reaction with epoxy groups. Two distinct lectins with different specificities, Sambucus sieboldiana agglutinin and concanavalin A, are effectively immobilized on SPM without impacting the binding activity. Moreover, high recovery rates of liposomal nanoparticles as a model of EVs are achieved due to the large flow-through pores (>10 μm) of SPM compared to a typical agarose gel. Finally, lectin-immobilized SPMs are employed to classify EVs based on the surface glycan structures and demonstrate different subpopulations by proteome profiling. This is the first approach to clarify the variation of protein contents in EVs by the difference of surface glycans via lectin immobilized media.

Label-free designed nanomaterials enrichment and separation techniques for phosphoproteomics based on mass spectrometry

The surface chemical characteristics of nanomaterials have a substantial impact on the affinity probe used to enrich proteins and peptides for MALDI-MS analysis of a real human sample. Detecting phosphoproteins involved in signalling is always difficult, even with recent developments in mass spectrometry, because protein phosphorylation is often temporary from complicated mixtures. This review summarizes current research on the successful enrichment of various intriguing glycoproteins and glycol peptides using surface affinity materials with distinctive qualities such as low cost, excellent structural stability, diversity, and multifunction. As a consequence, this review will provide a quick overview of the scholars from various backgrounds who are working in this intriguing interdisciplinary field. Label-free cancer biomarkers and other diseases will benefit from future challenges.

Separation of Glycoproteins Based on Sugar Chains Using Novel Stationary Phases Modified with Poly(ethylene glycol)-Conjugated Boronic-Acid Derivatives

Boronic acid (BA) reversibly complexes with the diol structure. BA derivatives separate glycoproteins based on the differences in the sugar chains. Separation typically occurs under basic conditions, which does not guarantee the structural stability of glycoproteins. Here, 5-boronopicolinic acid (BPA) is used to prepare silica-gel based columns with poly(ethylene glycol) (PEG) as a linker to suppress nonselective adsorption and poly(ethylene imine) (PEI) as a scaffold to increase the BPA moiety density. High-performance liquid chromatography (HPLC) using only aqueous buffer solutions without organic solvents demonstrates the selective retention ability of the BPA columns for glycoproteins. BPA interacts with the diols in the sugar chains but not the proteins. In an evaluation for N-glycans, the BPA columns show a higher retention ability toward high mannose type and a lower affinity to N-acetylneuraminic acid (Neu5Ac). Finally, a pair of glycoproteins, fetuin and asialofetuin, are selectively separated due to the presence of Neu5Ac on the nonreducing end.

Polyamidoamine dendrimer-assisted 3-carboxybenzoboroxole-functionalized magnetic nanoparticles for highly efficient capture of trace cis-diol-containing biomacromolecules

Boronate affinity materials have attracted more and more attention in recent years due to their highly selective capture of cis-diol-containing biomacromolecules.

Recent Advances in Lectin-Based Affinity Sorbents for Protein Glycosylation Studies

Glycosylation is one of the most significant post-translational modifications occurring to proteins, since it affects some of their basic properties, such as their half-life or biological activity. The developments in analytical methodologies has greatly contributed to a more comprehensive understanding of the quantitative and qualitative characteristics of the glycosylation state of proteins. Despite those advances, the difficulty of a full characterization of glycosylation still remains, mainly due to the complexity of the glycoprotein and/or glycopeptide mixture especially when they are present in complex biological samples. For this reason, various techniques that allow a prior selective enrichment of exclusively glycosylated proteins or glycopeptides have been developed in the past and are coupled either on- or off- line with separation and detection methods. One of the most commonly implemented enrichment methods includes the use of lectin proteins immobilized on various solid supports. Lectins are a group of different, naturally occurring proteins that share a common characteristic, which concerns their affinity for specific sugar moieties of glycoproteins. This review presents the different formats and conditions for the use of lectins in affinity chromatography and in solid phase extraction, including their use in dispersive mode, along with the recent progress made on either commercial or home-made lectin-based affinity sorbents, which can lead to a fast and automated glycosylation analysis.

Boronic acid-functionalized spherical polymer brushes for efficient and selective enrichment of glycoproteins

Glycoproteins are related to many biological activities and diseases, and thereby their efficient capture and enrichment for diagnostics and proteomics have emerged to exhibit great significance. However, the lack of materials with high binding capacity and selectivity is still a big obstacle for further application. Herein, we reported a facile and eco-friendly approach to fabricate spherical polymer brushes with multiple boronic acid groups. Specifically, the whole process can be divided into three steps, the polystyrene (PS) core was obtained by traditional emulsion polymerization, followed by immobilization of a home-made photoinitiator. Subsequently, boronic acid-functionalized polymer chains (PBA) were chemically grafted via photo-emulsion polymerization, leading to spherical polymer brushes (PS-PBA) with boronate affinity. The particle size, morphology, and composition of as-prepared spherical polymer brushes were systematically characterized. The characteristics of glycoproteins binding to the spherical polymer brushes under different conditions, including pH values and ionic strength, were also investigated. PS-PBA brushes possess fast binding speed (30 min) and high binding capacity for glycoprotein ovalbumin (OVA) (377.0 mg g^-1) under physiological pH conditions at 25 °C, because the low steric hindrance of flexible polymeric PBA chains facilitates the interaction between boronic acid groups and glycoproteins. Moreover, the binding capacity of PS-PBA brushes for glycoprotein OVA was ∼6.7 times higher than that for non-glycoprotein bovine serum albumin (BSA), indicating the excellent selective adsorption. This study provided a facile and efficient approach for the fabrication of boronic acid-functionalized materials that will be useful in the enrichment and separation of glycoproteins for the diagnosis of diseases.

The molecular imprinting of magnetic nanoparticles with boric acid affinity for the selective recognition and isolation of glycoproteins

A strategy was designed for the molecular imprinting of magnetic nanoparticles with boric acid affinity (MNPs@MIP) which were then used for the selective recognition and isolation of glycoproteins. Fe₃O₄ nanoparticles were prepared by a solvothermal method and direct silanization by the condensation polymerization of aminopropyltriethoxysilane (APTES). Subsequently, phenylboric acid was functionalized by reductive amination between 2,3-difluoro-4-formyl phenylboric acid (DFFPBA) and the amido group. The resultant Fe₃O₄@SiO₂–DFFPBA was then used for the selective adsorption of a glycoprotein template. Finally, a molecularly imprinted layer was covered on the surface nanoparticles by the condensation polymerization of tetraethyl orthosilicate (TEOS). The adsorption capacities of the resultant MNPs@MIP–HRP and MNPs@MIP–OVA to horseradish peroxidase (HRP) or ovalbumin (OVA) were significantly higher than non-imprinted particles (MNPs@NIP). Moreover, the adsorption capacities of MNPs@MIP–HRP and MNPs@MIP–OVA on non-template protein and non-glycoprotein bovine serum albumin (BSA) were significantly lower than those of their respective template proteins, thus indicating that both of the prepared MNPs@MIP exhibited excellent selectivity.

A strategy was designed for the preparation of molecular imprinting of magnetic nanoparticles with boric acid affinity (MNPs@MIP), and the resultant MNPs@MIP exhibited excellent selectivity for template glycoproteins.

Boronoisophthalic acid as a novel affinity ligand for the selective capture and release of glycoproteins near physiological pH

Boronic acid-based affinity materials have gained tremendous attention for the selective separation and recognition of cis-diol containing biomolecules. But often, these boronate affinity materials are stuck to some serious issues like high binding pH and weak affinity, especially in the case of glycoproteins. Here in this study, we used 5-boronoisophthlic acid as a novel affinity ligand for the selective capture and release of glycoproteins. The pKa value of 5-boronoisophthalic acid is investigated to be 7.8 which is just closed to physiological pH and is ideally suitable for the fast binding and elution kinetics of glycoproteins to avoid their degradation and deactivation. The affinity ligand is attached to the surface of polymer support using branched polyethyleneimine (PEI) which enhances the binding strength as it has multiple amine groups available for the attachment of 5-boronoisophthalic for synergistic interactions. The resulting affinity material is characterized and packed in a micropipette-tip using hydrophilic melamine foam as a frit to make the separation process smooth, simple, reliable, and robust. This boronic acid-based affinity tip exhibits binding constants for model glycoproteins in the range of 10^-6-10^-7 M, binding capacities in the range of 0.662 μM/g, and selectivity up to 1:1000 (HRP to BSA) under optimized extraction conditions. Finally, the boronic-based affinity tip is successfully applied to selectively capture the glycoproteins from the human milk sample, especially lactoferrin which is highly important in dairy manufacture.

Development and evaluation of silica-based lectin microcolumns for glycoform analysis of alpha1-acid glycoprotein

Silica-based lectin microcolumns were developed and optimized for the separation and analysis of glycoform fractions in alpha1-acid glycoprotein (AGP) based on both the degree of branching and level of fucosylation. Concanavalin A (Con A) and Aleuria Aurantia lectin (AAL) were immobilized onto HPLC-grade silica by reductive amination and packed into 2.1 mm i.d. × 5.0 cm microcolumns. Factors examined for these microcolumns include their protein content, binding capacity, binding strength and band-broadening under isocratic conditions (Con A) or step elution conditions (AAL) and in the presence of various flow rates or temperatures. These factors were examined by using experiments based on frontal analysis, zonal elution, peak profiling and peak decay analysis. Up to 200 μg AGP could be loaded onto a Con A microcolumn and provide linear elution conditions, and 100 μg AGP could be applied to an AAL microcolumn. The final conditions for separating retained and non-retained AGP glycoform fractions on a Con A microcolumn used a flow rate of 50 μL min-1 and a temperature of 50 °C, which gave a separation of these fractions within 20 min or less. The final conditions for an AAL microcolumn included a flow rate of 0.75 mL min-1, a temperature of 50 °C, and the use of 2.0 mM l-fucose as a competing agent for elution, giving a separation of non-retained and retained AGP glycoforms in 6 min or less. The inter-day precisions were ±0.7-4.0% or less for the retention times of the AGP glycoforms and ±2.2-3.0% or less for their peak areas.

DMSA-Functionalized Mesoporous Alumina with a High Capacity for Selective Isolation of Immunoglobulin G

A novel dimercaptosuccinic acid-functionalized mesoporous alumina (DMSA-MA) is synthesized by the dicarboxylic acid groups of dimercaptosuccinic acid molecules coordinating to the Al³⁺ ions located in the mesostructure. The as-prepared DMSA-MA composites possess a large surface area of 91.17 m²/g as well as a uniform pore size and a high pore volume of 17.22 nm and 0.23 cm³/g, respectively. DMSA coating of mesostructures significantly enhanced their selectivity for glycoprotein adsorption through a powerful hydrophilic binding force, and the maximum adsorption capacity of immunoglobulin G (IgG) can reach 2298.6 mg g^-1. The captured IgG could be lightly stripped from the DMSA-MA composites with an elution rate of 98.3% by using 0.5 wt % CTAB solution as the elution reagent. DMSA-MA is further employed as a sorbent for the enrichment of IgG heavy chain and light chain from human serum sample. SDS-PAGE assay results showed the obtained IgG with high purity compared to that of the standard solution of IgG.

Optimization of protein entrapment in affinity microcolumns using hydrazide-activated silica and glycogen as a capping agent

Several approaches were compared for the entrapment of proteins within hydrazide-activated silica for use in affinity microcolumns and high performance affinity chromatography. Human serum albumin (HSA) and concanavalin A (Con A) were used as model proteins for this work. Items considered in this study included the role played by the solution volume, amount of added protein, and use of slurry vs. on-column entrapment on the levels of solute retention and extent of protein immobilization that could be obtained by means of entrapment. The levels of retention and protein immobilization were evaluated by injecting warfarin or 4-methylumbellipheryl α-D-mannopyranoside as solutes with known binding properties for HSA or Con A. Altering both the solution volume and amount of added protein led to an increase of up to 17-fold in the extent of protein immobilization for HSA in slurry-based entrapment; on-column entrapment provided an additional 3.6-fold increase in protein content vs. the optimized slurry method. Similar general trends were seen for Con A. The protein contents obtained by entrapment for HSA or Con A (i.e., up to ~87 and 46 mg/g silica, respectively) were comparable to or higher than levels reported for the covalent immobilization of these proteins onto silica. The retention of warfarin on the entrapped HSA was at least 1.7-fold higher than has been obtained under comparable support and mobile phase conditions when using covalent immobilization. These results indicated that entrapment can be an attractive alternative to covalent immobilization for proteins such as HSA and Con A, with this approach serving as a potential means for obtaining good solute binding and retention in work with affinity microcolumns or related microscale devices.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. 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. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Facile preparation of microporous organic polymers functionalized macroporous hydrophilic resin for selective enrichment of glycopeptides

A macroporous adsorption resin (MAR) with ∼10 μm diameter was synthesized by seed-swelling polymerization and further modified with a layer of microporous organic polymers (MOP) by "one-pot" solvothermal reaction. The resulting MAR@MOP exhibited high specific surface area of 131.3 m²/g, which was higher than that of pristine MAR (57.8 m²/g). The contact angle also decreased from 58.8° (MAR) to 24° (MAR@MOP), indicating that the MOP was successfully grafted onto the surface of MAR. The chemical composition of MAR@MOP was confirmed by Fourier-transform infrared spectroscopy, ¹³C NMR and element analysis. The enrichment efficiency of MAR@MOP to glycopeptides was demonstrated by trapping N-linked glycopeptides from tryptic digests of human immunoglobulin G (IgG), horseradish peroxidase (HRP) and bovine fetuin. Furthermore, 879 unique N-glycosylation sites in 811 unique glycopeptides sequence mapped to 516 N-glycosylated proteins were identified in three replicate analyses of proteins extracted from mouse liver. Therefore, this hydrophilic MOP-coated adsorbent would be applied in the enrichment and identification of low-abundance N-linked glycopeptides in complicated biological samples.

Branched polyethyleneimine-assisted boronic acid-functionalized silica nanoparticles for the selective enrichment of trace glycoproteins

Boronate affinity materials have attracted more and more attention in extraction, separation and enrichment of glycoproteins due to the important roles that glycoproteins take on in recent years. However, conventional boronate affinity materials suffer from low binding affinity mainly because of the use of single boronic acids. This makes the extraction of glycoproteins of trace concentration become rather difficult or impossible. Here we present a novel boronate avidity material, polyethyleneimine (PEI)-assisted boronic acid-functionalized silica nanoparticles (SNPs). Branched PEI was applied as a scaffold to amplify the number of boronic acid moieties. While 3-carboxybenzoboroxole, exhibiting high affinity and excellent water solubility toward glycoproteins, was used as an affinity ligand. Due to the PEI-assisted synergistic multivalent binding, the boronate avidity SNPs exhibited strong binding strength toward glycoproteins with dissociation constants of 10^-7 M, which was the highest among reported boronic acid-functionalized materials that can be applied for glycoproteomic analysis. Such a high avidity enabled the selective extraction of trace glycoproteins as low as 0.4 pg/mL. This feature greatly favored the selective enrichment of trace glycoproteins from real samples. Meanwhile, the boronate avidity SNPs was tolerant of the interference of abundant sugars. In addition, the PEI-assisted boronate avidity SNPs exhibited high binding capacity and low binding pH. The feasibility for practical applications was demonstrated with the selective enrichment of trace glycoproteins in human saliva.

High performance affinity chromatography and related separation methods for the analysis of biological and pharmaceutical agents

The last few decades have witnessed the development of many high-performance separation methods that use biologically related binding agents. The combination of HPLC with these binding agents results in a technique known as high performance affinity chromatography (HPAC). This review will discuss the general principles of HPAC and related techniques, with an emphasis on their use for the analysis of biological compounds and pharmaceutical agents. Various types of binding agents for these methods will be considered, including antibodies, immunoglobulin-binding proteins, aptamers, enzymes, lectins, transport proteins, lipids, and carbohydrates. Formats that will be discussed for these methods range from the direct detection of an analyte to indirect detection based on chromatographic immunoassays, as well as schemes based on analyte extraction or depletion, post-column detection, and multi-column systems. The use of biological agents in HPLC for chiral separations will also be considered, along with the use of HPAC as a tool to screen or study biological interactions. Various examples will be presented to illustrate these approaches and their applications in fields such as biochemistry, clinical chemistry, and pharmaceutical research.

Progress of recyclable magnetic particles for biomedical applications

The preparation, types, recycling methods, biomedical applications and outlook of recyclable magnetic particles have been reviewed.

Functional dual hydrophilic dendrimer-modified metal-organic framework for the selective enrichment of N-glycopeptides

Analysis of protein glycosylation remains a significant challenge due to the low abundance of glycoproteins or N-glycopeptides. Here we have synthesized an amino-functionalized metal-organic framework (MOF) MIL-101(Cr)-NH₂ whose surface is grafted with a hydrophilic dendrimer poly(amidoamine) (PAMAM) for N-glycopeptide enrichment based on the hydrophilic interactions. The selected substrate MOF MIL-101(Cr) owns high surface area which provides nice support for peptide adsorption. In addition, the MOF displayed a good hydrophilic property after being modified with amino groups. Most importantly, the grafted hydrophilic dendrimer PAMAM was firstly applied in the postsynthetic modification of MOFs. And this functionalization route using macromolecular dendrimer opens a new perspective in MOFs design. Owing to its long dendritic chains and abundant amino groups, our material displayed dual hydrophilic property. In the enrichment of standard glycoprotein HRP digestion, the functional MOF material was shown to have low detection limit (1 fmol/μL) and good selectivity when the concentration of nonglycopeptides was 100 fold higher than the target N-glycopeptides. All the results proved that MIL-101(Cr)-NH₂ @PAMAM has great potential in the glycoproteome analysis.

Recent advances in capillary ultrahigh pressure liquid chromatography

In the twenty years since its initial demonstration, capillary ultrahigh pressure liquid chromatography (UHPLC) has proven to be one of most powerful separation techniques for the analysis of complex mixtures. This review focuses on the most recent advances made since 2010 towards increasing the performance of such separations. Improvements in capillary column preparation techniques that have led to columns with unprecedented performance are described. New stationary phases and phase supports that have been reported over the past decade are detailed, with a focus on their use in capillary formats. A discussion on the instrument developments that have been required to ensure that extra-column effects do not diminish the intrinsic efficiency of these columns during analysis is also included. Finally, the impact of these capillary UHPLC topics on the field of proteomics and ways in which capillary UHPLC may continue to be applied to the separation of complex samples are addressed.

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.

Temperature and pH Dual-Responsive Core-Brush Nanocomposite for Enrichment of Glycoproteins

In this report, we present a novel modular approach to the immobilization of a high density of boronic acid ligands on thermoresponsive block copolymer brushes for effective enrichment of glycoproteins via their synergistic multiple covalent binding with the immobilized boronic acids. Specifically, a two-step, consecutive surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to graft a flexible block copolymer brush, pNIPAm-b-pGMA, from an initiator-functionalized nanosilica surface, followed by postpolymerization modification of the pGMA moiety with sodium azide. Subsequently, an alkyne-tagged boronic acid (PCAPBA) was conjugated to the polymer brush via a Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction, leading to a silica-supported polymeric hybrid material, Si@pNIPAm-b-pBA, with a potent glycol binding affinity. The obtained core-brush nanocomposite was systematically characterized with regard to particle size, morphology, organic content, brush density, and number of immobilized boronic acids. We also studied the characteristics of glycoprotein binding of the nanocomposite under different conditions. The nanocomposite showed high binding capacities for ovalbumin (OVA) (98.0 mg g^-1) and horseradish peroxidase (HRP) (26.8 mg g^-1) in a basic buffer (pH 9.0) at 20 °C. More importantly, by adjusting the pH and temperature, the binding capacities of the nanocomposite can be tuned, which is meaningful for the separation of biological molecules. In general, the synthetic approach developed for the fabrication of block copolymer brushes in the nanocomposite opened new opportunities for the design of more functional hybrid materials that will be useful in bioseparation and biomedical applications.

pH-Responsive magnetic metal-organic framework nanocomposites for selective capture and release of glycoproteins

Novel magnetic metal-organic framework nanocomposites with 1,4-phenylenebisboronic acid as both an organic ligand and a functional molecule are proposed for the first time as a new type of intelligent nanomaterial to selectively capture and release glycoproteins via pH-stimulus-response, and would be of great potential for use in bio-separation.

Application of Porous Materials to Carbohydrate Chemistry and Glycoscience

There is a growing interest in using a range of porous materials to meet research needs in carbohydrate chemistry and glycoscience in general. Among the applications of porous materials reviewed in this chapter, enrichment of glycans from biological samples prior to separation and analysis by mass spectrometry is a major emphasis. Porous materials offer high surface area, adjustable pore sizes, and tunable surface chemistry for interacting with glycans, by boronate affinity, hydrophilic interactions, molecular imprinting, and polar interactions. Among the materials covered in this review are mesoporous silica and related materials, porous graphitic carbon, mesoporous carbon, porous polymers, and nanoporous gold. In some applications, glycans are enzymatically or chemically released from glycoproteins or glycopeptides, and the porous materials have the advantage of size selectivity admitting only the glycans into the pores and excluding proteins. Immobilization of lectins onto porous materials of suitable pore size allows for the use of lectin-carbohydrate interactions in capture or separation of glycoproteins. Porous material surfaces modified with carbohydrates can be used for the selective capture of lectins. Controlled release of therapeutics from porous materials mediated by glycans has been reported, and so has therapeutic targeting using carbohydrate-modified porous particles. Additional applications of porous materials in glycoscience include their use in the supported synthesis of oligosaccharides and in the development of biosensors for glycans.

Branched polyethyleneimine-assisted boronic acid-functionalized magnetic nanoparticles for the selective enrichment of trace glycoproteins

Boronate affinity materials, as efficient sorbents for extraction, separation and enrichment of glycoproteins, have attracted more and more attention in recent years.

pH-Responsive magnetic nanospheres for the reversibly selective capture and release of glycoproteins

We present a pH-stimuli-responsive strategy to reversibly capture and release glycoproteins with high selectivity from a pure protein, model protein mixture and even a real biological sample.

Selective extraction of bioactive glycoprotein in neutral environment through Concanavalin A mediated template immobilization and dopamine surface imprinting

Inspired by the sugar–lectin interaction, Concanavalin A mediated glycoprotein pre-immobilization, combined with dopamine polymerization, is employed to fabricate a glycoprotein imprint that can work in physiological environments.

Polyethyleneimine-modified graphene oxide nanocomposites for effective protein functionalization

A facile method to prepare a biocompatible graphene oxide (GO)-based substrate for protein immobilization was developed to overcome the drawbacks of GO, such as the strong electrostatic and hydrophobic interactions which could potentially alter the conformation and biological activity of proteins. The GO was coated with hydrophilic branched polyethyleneimine (BPEI), while Concanavalin A (Con A) as a model lectin protein was employed to fabricate the functionalized composites to evaluate the feasibility of this strategy. The composites exhibit an extremely high binding capacity for glycoproteins (i.e. IgG 538.3 mg g(-1)), which are superior to other immobilized materials. Moreover, they can work well in 500-fold non-glycoprotein interference and even in complex biological samples. All these data suggest that the GO@BPEI composites will have great potential as scaffolds for proteins fully exerting their biofunctions.

Multilayer Hydrophilic Poly(phenol-formaldehyde resin)-Coated Magnetic Graphene for Boronic Acid Immobilization as a Novel Matrix for Glycoproteome Analysis

Capturing glycopeptides selectively and efficiently from mixed biological samples has always been critical for comprehensive and in-depth glycoproteomics analysis, but the lack of materials with superior capture capacity and high specificity still makes it a challenge. In this work, we introduce a way first to synthesize a novel boronic-acid-functionalized magnetic graphene@phenolic-formaldehyde resin multilayer composites via a facile process. The as-prepared composites gathered excellent characters of large specific surface area and strong magnetic responsiveness of magnetic graphene, biocompatibility of resin, and enhanced affinity properties of boronic acid. Furthermore, the functional graphene composites were shown to have low detection limit (1 fmol) and good selectivity, even when the background nonglycopeptides has a concentration 100 fold higher. Additionally, enrichment efficiency of the composites was still retained after being used repeatedly (at least three times). Better yet, the practical applicability of this approach was evaluated by the enrichment of human serum with a low sample volume of 1 μL. All the results have illustrated that the magG@PF@APB has a great potential in glycoproteome analysis of complex biological samples.

A pH-responsive soluble polymer-based homogeneous system for fast and highly efficient N-glycoprotein/glycopeptide enrichment and identification by mass spectrometry

A homogeneous reaction system was developed for facile and highly efficient enrichment of biomolecules by exploiting the reversible self-assembly of a stimuli-responsive polymer.

Liquid phase homogeneous reactions using soluble polymer supports have found numerous applications in homogeneous catalysis and organic synthesis because of their advantages of no interface mass transfer limitation and a high conversion rate. However, their application in analytical separation is limited by the inefficient/inconvenient recovery of the target molecules from the extremely complex biological samples. Here, we report a stimuli-responsive polymer system for facile and efficient enrichment of trace amounts of biomolecules from complex biological samples. The soluble polymer supports provide a homogeneous reaction system with fast mass transfer and facilitate interactions between the supports and the target molecules. More importantly, the stimuli-responsive polymers exhibit reversible self-assembly and phase separation under pH variations, which leads to facial sample recovery with a high yield of the target biomolecules. The stimuli-responsive polymer is successfully applied to the enrichment of low abundant N-glycoproteins/glycopeptides, which play crucial roles in various key biological processes in mammals and are closely correlated with the occurrence, progression and metastasis of cancer. N-Glycoprotein is coupled to the stimuli-responsive polymer using the reported hydrazide chemistry with pre-oxidation of the oligosaccharide structure. Highly efficient enrichment of N-glycoproteins/N-glycopeptides with >95% conversion rate is achieved within 1 h, which is eight times faster than using solid/insoluble hydrazide enrichment materials. Mass spectrometry analysis achieves low femtomolar identification sensitivity and obtained 1317 N-glycopeptides corresponding to 458 N-glycoproteins in mouse brain, which is more than twice the amount obtained after enrichment using commercial solid/insoluble materials. These results demonstrate the capability of this “smart” polymer system to combine stimuli-responsive and target-enrichment moieties to achieve improved identification of key biological and disease related biomolecules.

Macroporous silica particles derivatized for enhanced lectin affinity enrichment of glycoproteins

This chapter details procedures for (1) functionalizing macroporous silica particles with lectins, a class of proteins that have affinity for the glycan moieties on glycoproteins, and (2) utilizing the lectin-silica material for high-performance affinity chromatography (HPAC) to enrich glycoproteins from small volumes of biological sample materials.

Fabrication of a dendrimer-modified boronate affinity material for online selective enrichment of cis-diol-containing compounds and its application in determination of nucleosides in urine

A high binding capacity dendrimer-modified boronate affinity material (SiO₂@dBA) was synthesized and coupled with large-volume injection/online column-switching solid phase extraction to facilitate the determination process of cis-diols.

Liquid phase based separation systems for depletion, prefractionation, and enrichment of proteins in biological fluids and matrices for in-depth proteomics analysis-An update covering the period 2011-2014

This review article expands on the previous one (S. Selvaraju and Z. El Rassi, Electrophoresis 2012, 33, 74-88) by reviewing pertinent literature in the period extending from early 2011 to present. As the previous review article, the present one is concerned with proteomic sample preparation (e.g., depletion of high-abundance proteins, reduction of the protein dynamic concentration range, enrichment of a particular subproteome), and the subsequent chromatographic and/or electrophoretic prefractionation prior to peptide separation and identification by LC-MS/MS. This review article, however, is distinguished from its earlier version by expanding on capturing/enriching subphosphoproteomes by immobilized metal affinity chromatography and metal oxide affinity chromatography. Seventy-seven papers published in the period extending from mid-2011 to the present have been reviewed. By no means this review article is exhaustive, given the fact that its aim is to give a concise treatment of the latest developments in the field.

New GO-PEI-Au-L-Cys ZIC-HILIC composites: synthesis and selective enrichment of glycopeptides

GO-PEI-Au-L-Cys composites were synthesized via loading gold nanoparticles on a GO surface using polyethylenimine as reducing and stabilizing reagents, followed by L-cysteine immobilization through an Au-S bond. The composites were applied as a kind of novel ZIC-HILIC material to achieve highly selective enrichment of glycopeptides from biological samples.

Pyridinylboronic acid-functionalized organic-silica hybrid monolithic capillary for the selective enrichment and separation of cis-diol-containing biomolecules at acidic pH

Boronate affinity chromatography (BAC) is a unique means for the selective separation and enrichment of 1,2 and 1,3 cis-diol-containing compounds. However, conventional boronate affinity materials require a basic binding pH (usually≥8.5), which gives rise to not only inconvenience in operation but also the risk of degradation of labile compounds. Although the applicable pH has been expanded to 5.0 in recent years, the current boronate affinity materials still fail to meet the acidic pH end of frequently used biosamples, particularly urine (pH 4.5). In this study, we report a 3-pyridylboronic acid-functionalized organic-silica hybrid monolithic capillary that exhibited a binding pH of 4.5, the lowest so far in BAC. Such a binding pH enabled direct extraction of cis-diol-containing biomolecules such as nucleosides from urine samples without pH adjustment. The boronate affinity monolithic capillary showed enhanced affinity toward negatively charged cis-diol-containing analytes such as ribonucleotides. Moreover, it could function as an anion exchanger at acidic pH (∼2). The column was found to retain multiple compounds from urine, which can be assumed to be at least mostly if not entirely cis-diol-containing compounds.

Displacement-type quartz crystal microbalance immunosensing platform for ultrasensitive monitoring of small molecular toxins

A novel displacement-type quartz crystal microbalance (QCM) immunosensing strategy, based on glucose and its analogue dextran for concanavalin A (ConA) binding sites, was designed for ultrasensitive monitoring of small molecular biotoxins (brevetoxin B, PbTx-2, used as a model) with signal amplification on a graphene-functionalized sensing interface. To construct such a QCM immunosensing platform, phenoxy-functionalized dextran (DexP) was initially assembled onto the surface of graphene-coated QCM probe via the π-stacking interaction, and ConA-labeled monoclonal mouse anti-PbTx-2 capture antibody was then immobilized on the DexP-modified probe by dextran-ConA binding. Gold nanoparticle heavily functionalized with glucoamylase and bovine serum albumin-PbTx-2 (PbTx-2-BSA) conjugate was employed as the trace tag. A competitive-type immunoassay format was adopted for the online monitoring of PbTx-2 between anti-PbTx-2 antibody immobilized on the QCM probe and PbTx-2-BSA labeled on the gold nanoparticle. Accompanying the gold nanoparticle, the carried glucoamylase could hydrolyze amylopectin in glucose. The produced glucose competed with dextran for ConA and displaced the ConA-streptavidin-anti-PbTx-2 complex from the QCM probe, resulting in the frequency change. Under optimal conditions, the frequency of the QCM immunosensor was indirectly proportional to the concentration of target PbTx-2 in the sample and exhibited a dynamic range from 1.0 pg·mL(-1) to 10 ng·mL(-1) with a detection limit (LOD) of 0.6 pg·mL(-1) at the 3Sblank level. Intra- and interassay coefficients of variation were below 7.5% and 9.5%, respectively. In addition, the methodology was evaluated for analysis of PbTx-2 in 15 spiked seafood samples and showed good accordance between results obtained by the displacement-type QCM immunosensor and a commercialized enzyme-linked immunosorbent assay (ELISA) method.

Recent trends in analytical and structural glycobiology

The great complexity of glycosylated biomolecules necessitates a set of powerful analytical methodologies to reveal functionally important structural features. Mass spectrometry (MS), with its different ionization techniques, mass analyzers, and detection strategies, has become the most important analytical method in glycomic and glycoproteomic investigations. In combination with MS, microscale separations (based on capillary chromatography and electrophoresis) and carbohydrate microchemistry, we feature here conceptually important applications of the recent years. This review focuses on methodological advances pertaining to disease biomarker research, immunology, developmental biology, and measurements of importance to biopharmaceuticals. High-sensitivity determinations and sample enrichment/preconcentration are particularly emphasized in glycomic and glycoproteomic profiling.

Analytical glycobiology at high sensitivity: current approaches and directions

This review summarizes the analytical advances made during the last several years in the structural and quantitative determinations of glycoproteins in complex biological mixtures. The main analytical techniques used in the fields of glycomics and glycoproteomics involve different modes of mass spectrometry and their combinations with capillary separation methods such as microcolumn liquid chromatography and capillary electrophoresis. The need for high-sensitivity measurements have been emphasized in the oligosaccharide profiling used in the field of biomarker discovery through MALDI mass spectrometry. High-sensitivity profiling of both glycans and glycopeptides from biological fluids and tissue extracts has been aided significantly through lectin preconcentration and the uses of affinity chromatography.