Boronic acid-functionalized core-shell-shell magnetic composite microspheres for the selective enrichment of glycoprotein

Investigation of thermal properties and structural characterization of novel boron-containing Schiff base polymers

Three novel Schiff base polymers were synthesized by using the Schiff base monomer obtained using aldehyde containing boric acid and amines containing hydroxyl groups as the starting materials. The polymers were synthesized at the same temperature and using the same amount of oxidizing agent by the oxidative polycondensation method. The characterization of all polymers and monomers was achieved by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), nuclear magnetic resonance spectroscopy (1H-NMR), liquid chromatography-mass spectrometry (LC-MS), gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The thermal stability of these compounds was studied by employing thermogravimetric analysis (TGA), and thermodynamics parameters such as activation energy (Ea), enthalpy (∆H), entropy (∆S), and Gibbs free energy(∆G) for the decomposition process were calculated using the Flynn-Wall-Ozawa method.

Artificial antibody-antigen-directed immobilization of lipase for consecutive catalytic synthesis of ester: Benzyl acetate case study

A strategy based on artificial antibody-antigen recognition was proposed for the specific directed immobilization of lipase. The artificial antibody was synthesized using catechol as a template, α-methacrylic acid as a functional monomer, and Fe3O4 as the matrix material. Lipase was modified with 3,4-dihydroxybenzaldehyde as an artificial antigen. The artificial antibody can specifically recognize catechol fragment in the enzyme structure to achieve the immobilization of lipase. The immobilization amount, yield, specific activity, and immobilized enzyme activity were 13.2 ± 0.2 mg/g, 78.9 ± 0.4 %, 7.9 ± 0.2 U/mgprotein, and 104.6 ± 1.7 U/gcarrier, respectively. Moreover, the immobilized lipase exhibited strong reusability and regeneration ability. Additionally, the immobilized lipase successfully catalyzed the synthesis of benzyl acetate and demonstrated robust continuous catalytic activity. These results fully demonstrate the feasibility of the proposed artificial antibody-antigen-directed immobilization of lipase.

Electrospun Fiber Membrane with the Dual Affinity of Chelation and Covalent Interactions for the Efficient Enrichment of Glycoproteins

As important biomarkers of many diseases, glycoproteins are of great significance to biomedical science. It is essential to develop efficient glycoprotein enrichment platforms and investigate their adsorption mechanism. In this work, a conspicuous enrichment strategy for glycoproteins was developed by using an electrospun fiber membrane wrapped with polydopamine (PDA) and modified with 3-aminophenylboronic acid and nickel ions, named PAN/DA@PDA@APBA/Ni. The enrichment characteristics of PAN/DA@PDA@APBA/Ni toward glycoproteins were explored through adsorption behavior. Thanks to the existence of two sites of interaction (metal ion chelation and boronate affinity), PAN/DA@PDA@APBA/Ni exhibited significant enrichment capacity for glycoproteins, ovalbumin (604.6 mg/g), and human immunoglobulin G (331.0 mg/g). The adsorption kinetic results of glycoprotein ovalbumin on PAN/DA@PDA@APBA/Ni conform to the pseudo-first-order kinetic model in the first adsorption stage, while the second half adsorption stage is more in line with the pseudo-second-order kinetic model. Moreover, the physical characteristics of PAN/DA@PDA@APBA/Ni and subsequent adsorption experiments on electrospun fiber modified with only phenylboronic acid or nickel ions both confirmed two sites of interaction (metal ion chelation and boronate affinity, respectively). Furthermore, a stepwise elution method with dual-affinity interaction was designed and successfully applied to enrich glycoproteins in real biological samples. This work provides an idea for sample pretreatment, especially for the design of dual-affinity materials in glycoproteins enrichment.

Facile fabrication of Ti4+-immobilized magnetic nanoparticles by phase-transitioned lysozyme nanofilms for enrichment of phosphopeptides

In this study, titanium (IV)-immobilized magnetic nanoparticles (Ti4+-PTL-MNPs) were firstly synthesized via a one-step aqueous self-assembly of lysozyme nanofilms for efficient phosphopeptide enrichment. Under physiological conditions, lysozymes readily self-organized into phase-transitioned lysozyme (PTL) nanofilms on Fe3O4@SiO2 and Fe3O4@C MNP surfaces with abundant functional groups, including -NH2, -COOH, -OH, and -SH, which can be used as multiple linkers to efficiently chelate Ti4+. The obtained Ti4+-PTL-MNPs possessed high sensitivity of 0.01 fmol μL-1 and remarkable selectivity even at a mass ratio of β-casein to BSA as low as 1:400 for phosphopeptide enrichment. Furthermore, the synthesized Ti4+-PTL-MNPs can also selectively identify low-abundance phosphopeptides from extremely complicated human serum samples and their rapid separation, good reproducibility, and excellent recovery were also proven. This one-step self-assembly of PTL nanofilms facilitated the facile and efficient surface functionalization of various nanoparticles for proteomes/peptidomes.

Glycan-selective in-situ growth of thermoresponsive polymers for thermoprecipitation and enrichment of N-glycoprotein/glycopeptides

In view of the biological significance and micro-heterogeneity of protein glycosylation for human health, specific enrichment of N-glycosylated proteins/peptides from complex biological samples is a prerequisite for the discovery of disease biomarkers and clinical diagnosis. In this work, we propose a "grafting-from" N-glycoprotein enriching method based on the in-situ growth of thermoresponsive polymer brushes from the N-glycosylated site of proteins. The initiator was first attached to the pre-oxidized glycan moieties by hydrazide chemistry, from which the thermoresponsive polymers can be grown to form giant protein-polymer conjugates (PPC). The thermosensitive PPC can be precipitated and separated by raising the temperature to above its lower critical solubility temperature (LCST). Mass spectrometry verified 210 N-glycopeptides corresponding to 136 N-glycoproteins in the rabbit serum. These results demonstrate the capability of the tandem thermoprecipitation strategy to enrich and separate N-glycoprotein/glycopeptide. Due to its simplicity and efficiency specifically, this method holds the potential for identifying biomarkers from biological samples in N-glycoproteome analysis.

Construction of a Carcinoembryonic Antigen Surface-Enhanced Raman Spectroscopy (SERS) Aptamer Sensor Based on the Silver Nanorod Array Chip

Carcinoembryonic antigen (CEA) is a cancer-related tumor marker, which is commonly used for preventive screening, auxiliary diagnosis, and recurrence monitoring. Therefore, it is of great significance to develop a new CEA detection method. In this paper, we developed an SERS aptasensor for CEA based on silver nanorod array chip, thiol aptamer, and 4-mercaptophenylboronic acid (4-MPBA). The silver nanorod array chip modified by CEA thiol aptamer (aptamer-SH) was used as SERS capture substrates. Ag@4-MPBA was used as a surface-enhanced Raman spectroscopy (SERS) tag. This proposed SERS aptasensor could detect CEA down to 0.447 pg·mL^-1 with a wide linear range from 1 pg·mL^-1 to 100 ng·mL^-1 (R² = 0.9907). The recovery of the standard addition test for CEA in serum was between 97.25% and 102.67%, and the RSD ≤ 2.52% (n = 3). The sensor has the advantages of good specificity, high sensitivity, and a wide linear range. It provides a new method for the detection of CEA in serum.

Molecularly imprinted polymers for selective extraction/microextraction of cancer biomarkers: A review

Over recent years, great efforts have been extensively documented in top scientific journals on the development of methods for early diagnosis, treatment, and monitoring of cancers which are prevalent critical diseases with a high mortality rate among men and women. The determination of cancer biomarkers using different optimum methodologies is one of the finest options for achieving these goals with more precision, speed, and at a lower cost than traditional clinical procedures. In this regard, while focusing on specific biomarkers, molecularly imprinted technology has enabled novel diagnostic techniques for a variety of diseases. Due to the well-known advantages of molecularly imprinted polymers (MIPs), this review focuses on the current trends of MIPs-based extraction/microextraction methods, specifically targeting cancer biomarkers from various matrices. These optimized methods have demonstrated high selectivity, accuracy, sorbent reusability, extraction recovery, and low limits of detection and quantification for a variety of cancer biomarkers, which are a powerful tool to provide early diagnosis, prognosis, and treatment monitoring, with potential clinical application expected soon. This review highlights the key progress, specific modifications, and strategies used for MIP synthesis. The future perspectives for cancer biomarkers purification and determination by fabricating MIP-based techniques are also discussed.

Fabrication of a sugar-immobilized fluorescent PMMA shell on a Ni core particle via soap-free emulsion polymerization

Sugar chain immobilized polymer particles having both magnetic and fluorescent properties can be expected to be useful in a wide variety of biomedical applications such as the detection, separation, and purification of proteins, viruses, or bacteria, because sugar chains specifically adsorb them. Since high magnetic responsiveness is required for such applications, we attempted to fabricate core-shell particles consisting of a submicron-sized magnetic core and a thin polymer shell (nano- to dozens of nanometers thick) that incorporates a fluorescent dye, with sugar molecules immobilized on the surface. Soap-free emulsion polymerization using methyl methacrylate (MMA) monomer and potassium persulfate (KPS) initiator in the presence of aminopropyltrimethoxysilane-treated Ni particles, octyl-β-D-glucopyranoside (octyl-glc), and rhodamine B (RhB) produced a glucose-immobilized fluorescent PMMA thin shell on a Ni particle (Ni/PMMA/RhB/octyl-glc). Electrostatic interaction was used both to incorporate RhB into the PMMA shell and to coat the Ni core with the PMMA-RhB shell. Glucose was immobilized on the PMMA shell by embedding a hydrophobic octyl group derived from octyl-glc in the PMMA matrix, and the resulting sugar-immobilized PMMA shell was able to adsorb protein (concanavalin A; a protein that specifically adsorbs glucose). The resulting Ni/PMMA/RhB/octyl-glc particles were well-dispersed in water, detected by highly sensitive fluorescence techniques, and could be collected by a magnet within 10 sec. They are expected to be applied to detect biological substances such as various proteins and viruses by changing the glucose moiety of the particle surface to other functional glycans.

Magnetic phosphorylated chitosan composite as a novel adsorbent for highly effective and selective capture of lead from aqueous solution

Separating and recovering lead from heavy metal contaminated wastewater is crucial for the environment remediation and reutilization of lead resources. Herein, a novel adsorbent, the phosphorylated chitosan-coated magnetic silica nanoparticles (Fe₃O₄@SiO₂@CS-P), was successfully fabricated and applied to highly selective adsorption of lead. Competitive experiments were conducted in a multi-ion solution (7 metal ions coexist) at pH 6.0, Fe₃O₄@SiO₂@CS-P exhibited an excellent selectively for capturing lead with the distribution coefficient (0.75 L g^-1) more ten times than other metal, while Fe₃O₄@SiO₂@CS demonstrated a highly selective adsorption of silver. These implied that phosphorylation of adsorbent not only improves the sorption performance of lead, but also changes the selective adsorption of metal types. Acidity experiments can draw conclusions that Fe₃O₄@SiO₂@CS-P exhibited better acid resistance (with barely any iron leaching) than silica-uncoated adsorbent (Fe₃O₄@CS-P) at pH 1.0. Furthermore, the FTIR and XPS spectra after adsorption suggested that the high adsorption performance and selective capture lead were predominantly controlled by the coordination of the phosphate groups on the surface of the adsorbent. This work shows a broad prospect of developing a series of novel, acid-resistant, good reusable and rapidly separable magnetic materials that can be used to efficiently and selectively capture lead from aqueous solutions.

Nano- and Microspheres Containing Inorganic and Biological Nanoparticles: Self-Assembly and Electron Tomographic Analysis

Organofullerene amphiphiles show diverse behaviors in water, forming vesicles, micelles, Langmuir-Blodgett films, and anisotropic nanostructures. We found that gradual in situ protonation of an organic solution of (4-heptylphenyl)₅C₆₀^-K⁺ by water or buffer generates the corresponding protonated molecule, (4-heptylphenyl)₅C₆₀H, which self-assembles to form nano- and microspheres of organofullerene (fullerspheres) with uniform diameters ranging from 30 nm to 2.5 μm that are controlled by the preparation or pH of the buffer. By using an aqueous solution of an organic dye, inorganic nanoparticle, protein, and virus, we encapsulated these entities in the fullersphere. This approach via self-assembly is distinct from other preparations of organic core-shell particles that generally require polymerization for the construction of a robust shell. The sphere is entirely amorphous, thermally stable up to 300 °C under vacuum, and resistant to electron irradiation, and we found the unconventional utility of the sphere for electron tomographic imaging of nanoparticles and biomaterials.

Boron-Modified Defect-Rich Molybdenum Disulfide Nanosheets: Reducing Nonspecific Adsorption and Promoting a High Capacity for Isolation of Immunoglobulin G

A new type of boric acid derivative-modified molybdenum disulfide nanosheet was prepared by amination and sulfur chemical grafting, where lipoic acid, lysine, and 5-carboxybenzoboroxole were used as reactants. The two-dimensional composite, abbreviated as MoS₂-Lys-CBX, is an ultrathin nanosheet with a minimum unit of single or few layers. Compared with the original molybdenum disulfide, the nonspecific adhesion of interfering proteins on the surface was reduced, and the adsorption capacity of glycoproteins was enhanced, which was 1682.2 mg g^-1 represented by IgG. The adsorbed IgG can be easily eluted with 0.3 wt % CTAB with an elution efficiency of 94.1%. Circular dichroism spectra indicate no obvious conformation change of IgG during the purification process by the MoS₂-Lys-CBX nanosheets. The as-prepared MoS₂-Lys-CBX nanosheets were then employed for the isolation of IgG from human serum sample, obtaining high-purity light and heavy chains of IgG, as demonstrated by SDS-PAGE assays.

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.

A Temperature-Responsive Boronate Core Cross-Linked Star (CCS) Polymer for Fast and Highly Efficient Enrichment of Glycoproteins

Fast and highly efficient enrichment and separation of glycoproteins is essential in many biological applications, but the lack of materials with high capture capacity, fast, and efficient enrichment/separation makes it a challenge. Here, a temperature-responsive core cross-linked star (CCS) polymer with boronate affinity is reported for fast and efficient enriching and separating of glycoproteins from biological samples. The temperature-responsive CCS polymers containing boronic acid in its polymeric arms and poly(N-isopropyl acrylamide) in its cross-linked core are prepared using reversible addition-fragmentation chain transfer polymerization via an "arm-first" methodology. The soluble boronate polymeric arms of the CCS polymers provide a homogeneous reaction system and facilitate interactions between boronic acid and glycoproteins, which leads to a fast binding/desorption speed and high capture capacity. Maximum binding capacity of the prepared CCS polymer for horseradish peroxidase is determined to be 210 mg g^-1 , which can be achieved within 20 min. More interestingly, the temperature-responsive CCS polymers exhibit rapid reversible thermal-induced volume phase transition by increasing the temperature from 15 to 30 °C, resulting in a facile and convenient sample collection and recovery for the target glycoproteins. Finally, the temperature-responsive CCS polymer is successfully applied to enrichment of low abundant glycoproteins.

A facile and general approach for the preparation of boronic acid-functionalized magnetic nanoparticles for the selective enrichment of glycoproteins

Biomedical applications and biomarkers for early clinical diagnostics and the treatment of diseases demand efficient and selective enrichment platforms for glycoproteins.

Highly Efficient Separation of Glycoprotein by Dual-Functional Magnetic Metal-Organic Framework with Hydrophilicity and Boronic Acid Affinity

Protein glycosylation plays a critical role in post-translational modifications of proteins in the organism and is involved in many diseases. However, the huge challenge for glycoproteins to be highly specific isolated and adsorbed from complicated biological samples results from their low abundance and interference. In this work, a novel dual-functionalized magnetic metal-organic frameworks nanoparticle for selective enrichment of glycoproteins was synthesized for the first time. Due to the abundant amino groups and grafted phenylboronic acid, the proposed nanoparticles have the dual properties of hydrophilicity and boronic acid affinity. The obtained nanoparticles show high binding capacities toward glycoproteins under physiological state (pH 7.4) such as ovalbumin (327.28 mg/g), transferrin (241.17 mg/g), horseradish peroxidase (530.79 mg/g). Furthermore, the nanoparticles still have excellent enrichment performance after being used six times repeatedly. More importantly, the prepared nanoparticles also have great potential applications in the adsorption of glycoproteins from complex biological specimens.

The development of nanobiocatalysis via the immobilization of cellulase on composite magnetic nanomaterial for enhanced loading capacity and catalytic activity

In this study, graphene oxide (GO) decorated with 4arm‑PEG‑NH₂ (molecular weight (MW) 5 K or 10 K) was constructed on magnetic Fe₃O₄, denoted as GO@Fe₃O₄@4arm‑PEG‑NH₂. The morphology, structure and magnetic property of GO@Fe₃O₄@4arm‑PEG‑NH₂ were characterized by Fourier transform infrared (FTIR), vibrating-sample magnetometer (VSM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in details. The saturation loading capacity of GO@Fe₃O₄@4arm‑PEG‑NH₂ (MW 5 K and 1 K) carriers toward cellulase was 429 and 575 mg/g, respectively. Additionally, the immobilized cellulase had exhibited enhanced thermostability, storability and reusability than free enzyme. The two kinds of immobilized cellulose (MW 5 K and 10 K) retained 57% and 60% of its initial activity after 3 h at 70 °C, and retained 47% and 50% of its initial activity after 30 days' storage at room temperature. After eight times reuse, immobilized cellulose (MW 5 K and 10 K) retained 40% and 45% of its initial activity, respectively. In practical application, glucose generated by the saccharification with the immobilized cellulase was much higher than free enzyme (immobilized enzyme is kept at 2.04-2.83 times of the free enzyme), when the loading amount of enzyme was 2-8 mg, indicating the potential of the prepared biocatalyst.

Polymer-Functionalized Magnetic Nanoparticles: Synthesis, Characterization, and Methylene Blue Adsorption

The removal of methylene blue (MB) from wastewater has attracted global concerns. In this study, polymer-functionalized magnetic nanoparticles for MB removal, Fe₃O₄@SiO₂-MPS-g-AA-AMPS (FSMAA), were successfully synthesized by grafting acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) on the surface of vinyl-modified Fe₃O₄@SiO₂. With various characterization techniques, it was confirmed that the obtained FSMAA had a core⁻shell structure, a good magnetic property, and plenty of functional groups on its surface. MB adsorption experiments showed that the adsorption capacity of FSMAA was notably enhanced as the grafted monomer concentration and solution pH were increased. The adsorption kinetic data and isothermal data were well described by the pseudo-second-order kinetic model and the Langmuir model, respectively. The maximum adsorption capacity of FSMAA was 421.9 mg g^-1 with grafted monomer concentration at 2.0 mol L^-1 and solution pH at 9, much higher than those of other adsorbents stated in previous literatures. Based on XPS analysis, surface adsorption mechanism between FSMAA and MB was electrostatic interaction, hydrogen bonding, and hydrophobic interaction. Furthermore, FSMAA was effectively regenerated by acid pickling, and the remaining adsorption capacity was more than 60% after eight adsorption⁻regeneration cycles. All the results demonstrated the self-made FSMAA was a desirable adsorbent to remove MB from wastewater.

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.

Nanogel-Incorporated Injectable Hydrogel for Synergistic Therapy Based on Sequential Local Delivery of Combretastatin-A4 Phosphate (CA4P) and Doxorubicin (DOX)

Drug combination therapies employing dual-drug delivery systems offer an effective approach to reduce disadvantages of single-drug therapy, such as high dose and easy generation of drug resistance. Herein, a dual-drug delivery system based on nanogel-incorporated injectable hydrogel (NHG) was designed for sequential local delivery of combretastatin-A4 phosphate (CA4P) and doxorubicin (DOX) for antiangiogenesis and anticancer combination therapy. The injectable hydrogel was prepared for loading and quick release of hydrophilic drug CA4P, while the pH and redox stimuli-responsive nanohydrogels were incorporated into the injectable hydrogel by pH-responsive boronate ester bond for sustained long-term DOX delivery. The dual-drug-loaded NHG system released CA4P and DOX sequentially and exhibited high inhibitory activities on the cancer cell proliferation in vitro. It displayed superior therapeutic efficacy in vivo with only one single injection. Immunohistochemistry analyses suggested a synergistic therapeutic effect through tumor vascular collapse caused by CA4P and tumor cell apoptosis induced by DOX. The combination therapy of antiangiogenic and cytotoxic drugs using NHG delivery system offers a promising approach for improved cancer therapeutic efficacy. The nanogel-embedded injectable hydrogel can be employed as a universal drug carrier for local dual-drug delivery with sequential release behaviors by simple injection.

Recent advances in mass spectrometry-based glycoproteomics

Protein glycosylation plays fundamental roles in many biological processes as one of the most common, and the most complex, posttranslational modification. Alterations in glycosylation profile are now known to be associated with many diseases. As a result, the discovery and detailed characterization of glycoprotein disease biomarkers is a primary interest of biomedical research. Advances in mass spectrometry (MS)-based glycoproteomics and glycomics are increasingly enabling qualitative and quantitative approaches for site-specific structural analysis of protein glycosylation. While the complexity presented by glycan heterogeneity and the wide dynamic range of clinically relevant samples like plasma, serum, cerebrospinal fluid, and tissue make comprehensive analyses of the glycoproteome a challenging task, the ongoing efforts into the development of glycoprotein enrichment, enzymatic digestion, and separation strategies combined with novel quantitative MS methodologies have greatly improved analytical sensitivity, specificity, and throughput. This review summarizes current MS-based glycoproteomics approaches and highlights recent advances in its application to cancer biomarker and neurodegenerative disease research.

Highly selective and sensitive visualization and identification of glycoproteins using multi-functionalized soluble dendrimer

Glycoproteins are the most important and complex group of posttranslational modifications known in proteins. Many clinical biomarkers and therapeutic targets in cancer are glycoproteins. However, the isolation of glyco-specific antibodies and their poor stability remains a significant challenge in analytical method and diagnostic development. In this work, for the first time, we present a technology for highly efficient and selective glycosylation analysis on membrane without the use of glyco-specific antibodies. This approach, termed Nanopoly-BAV, which uses polyamidoamine dendrimers multifunctionalized with boronic acid for specific binding to glycoproteins and with biotin groups for glycoproteins visualization. The Nanopoly-BAV confers femtomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 100000 folds for glycoproteins over nonglycoproteins. This synthetic, robust and highly selective Nanopoly-BAV has a great potential to measure cell signaling events by clearly distinguishing actual glycosylation signals from protein expression changes with superior stability. This technique may provide a powerful tool to monitor cellular signaling pathways and discovering new signaling events.

Boronic Acid-Modified Magnetic Fe3O4@mTiO2 Microspheres for Highly Sensitive and Selective Enrichment of N-Glycopeptides in Amniotic Fluid

Although mesoporous materials and magnetic materials are used to enrich glycopeptides, materials sharing both mesoporous structures and magnetic properties have not been reported for glycopeptide analyses. Here we prepared boronic acid-modified magnetic Fe₃O₄@mTiO₂ microspheres by covalent binding of boronic acid molecules onto the surfaces of silanized Fe₃O₄@mTiO₂ microspheres. The final particles (denoted as B-Fe₃O₄@mTiO₂) showed a typical magnetic hysteresis curve, indicating superparamagnetic behavior; meanwhile, their mesoporous sizes did not change in spite of the reduction in surface area and pore volume. By using these particles together with conventional poly(methyl methacrylate) (PMMA) nanobeads, we then developed a synergistic approach for highly specific and efficient enrichment of N-glycopeptides/glycoproteins. Owing to the introduction of PMMA nanobeads that have strong adsorption towards nonglycopeptides, the number of N-glycopeptides detected and the signal-to-noise ratio in analyzing standard proteins mixture both increased appreciably. The recovery of N-glycopeptides by the synergistic method reached 92.1%, much improved than from B-Fe₃O₄@mTiO₂ alone that was 75.3%. Finally, we tested this approach in the analysis of amniotic fluid, obtaining the maximum number and ratio of N-glycopeptides compared to the use of B-Fe₃O₄@mTiO₂ alone and commercial SiMAG-boronic acid particles. This ensemble provides an interesting and efficient enrichment platform for glycoproteomics research.

Modification of bovine serum albumin with aminophenylboronic acid as glycan sensor based on surface plasmon resonance and isothermal titration calorimetry

Aminophenylboronic acid (ABA) modified bovine serum albumin (BSA) was prepared as neolectin and its interactions with oligosaccharides and glycopolymer were studied by surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). The conjugation between the primary amine group of the ABA molecule and lysine residues on BSA was performed with an adipate-based strategy to afford the synthetic neoprotein. The number of ABA molecules loaded to BSA surface was determined by matrix-assisted laser desorption/ionization – time of flight (MALDI-TOF) mass spectrometry. In the BSA-ABA and sugar interaction study, no signal was observed for both the SPR and ITC sensor platform using monosaccharides as the analyte, indicating a weak binding affnity, while the galactose modified polymer showed an enhanced response. The binding affinities of the galactosyl-polymer to BSA-ABA from SPR and ITC data were in the micromolar range.

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.

Eco-Friendly Composite of Fe3O4-Reduced Graphene Oxide Particles for Efficient Enzyme Immobilization

A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic composite particles of Fe₃O₄ and rGO containing 71% (rGO-Fe₃O₄-M1), 36% (rGO-Fe₃O₄-M2), and 18% (rGO-Fe₃O₄-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-Fe₃O₄ composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-Fe₃O₄-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure Fe₃O₄ and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-Fe₃O₄-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and Fe₃O₄ may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward Vibrio fischeri than commercial pure Fe₃O₄ particles.

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.

Phenylboronic acid-functionalized core–shell magnetic composite nanoparticles as a novel protocol for selective enrichment of fructose from a fructose–glucose aqueous solution

We developed an efficient and mild method for the preparation of boronic acid-functionalized magnetic nanoparticles (MNPs), and the selective separation of fructose from a sample solution was demonstrated for the first time.

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.