Glutathione-Functionalized Magnetic Covalent Organic Framework Microspheres with Size Exclusion for Endogenous Glycopeptide Recognition in Human Saliva

Progress in the application of functionalized covalent organic framework for bioanalysis

As a new type of crystalline porous polymer materials, covalent organic frameworks (COFs) with their unique features such as large surface area, tunable pore sizes, strong π-π stacking effect and size exclusion effects, have attracted wide attention in the analytical field. Due to the lack of catalytically active metal centers in bare COFs, functionalized COFs that are hybridized or modified with nanomaterials improve reactive activation and show better analytical performance for a variety of detection scenarios with complex analytes. Herein, we focused on the functionalized COFs used in bioanalysis ranging from nucleic acids, peptides, and proteins, to microorganisms, and discussed the functionalization strategy and unique structures and properties applied in the different stages of biosensing and advantages compared to other hybrid materials. Finally, challenges and future research directions of functionalized COFs in bioanalysis are discussed.

Advances in the development of N-glycopeptide enrichment materials based on hydrophilic interaction chromatography

Protein glycosylation is one of the most important post-translational modifications, implicated in the development of various diseases, including neurodegenerative diseases, diabetes, and cancers. However, the low content of glycoproteins in biological samples, the diversity and heterogeneity of glycan structures, and insensitive detection methods make glycosylation analysis challenging. As a result, efficient enrichment of glycopeptides from complex samples is a critical step. Efficient enrichment technology can increase the abundance of intact N-glycopeptides in complex biological samples, thereby improving the sensitivity and coverage of glycosylation analysis, which is of great significance for the accurate identification of biomarkers and the development of glycopeptide-based drugs. Among various separation methods for N-glycopeptides, hydrophilic interaction chromatography has received increasing attention, and a variety of enrichment materials have been developed. This article classifies and describes the relevant hydrophilic interaction chromatography materials and provides a comprehensive review of their applications in N-glycopeptide enrichment regarding selectivity, sensitivity, and enrichment performance. Future development trends of ideal glycopeptide enrichment materials are also discussed.

Effects of a Novel Magnetic Nanomaterial on Oral Biofilms

Dental caries is one of the most common oral chronic infectious diseases, and novel antibacterial materials must be developed to control plaque and inhibit formation of dental caries. Combining magnetic nanomaterials with antibacterial agents to decrease the formation of bacterial biofilm has been a hot topic in the biomedical field. The present study developed a novel magnetic nanomaterial chemically combined with dimethylaminododecyl methacrylate (DMADDM) and initially investigated its inhibiting effects on biofilms by using traditional caries-related bacteria and saliva flora models. The novel magnetic nanomaterials successfully loaded DMADDM according to thermogravimetric analysis, Fourier transform infrared spectroscopy, x-ray diffraction, vibrating sample magnetometry, scanning electron microscopy, and transmission electron microscopy results. Further, the novel nanoparticle Fe3O4@SiO2@DMADDM with concentration of 8 mg/mL could effectively reduce Streptococcus mutans biofilm and decrease the production of lactic acid. The 16S rDNA sequencing revealed that Fe3O4@SiO2@DMADDM could depress the proportion of caries-related bacteria in saliva-derived biofilm, such as Streptococcus, Veillonella, and Neisseria. Therefore, Fe3O4@SiO2@DMADDM is a novel effective antibacterial magnetic nanomaterial and has clinical potential in plaque control and dental caries prevention.

Covalent organic frameworks in cancer theranostics: advancing biomarker detection and tumor-targeted therapy

In recent years, covalent organic frameworks (COFs) have garnered considerable attention in the field of onco-nanotechnology as a new type of nanoporous construct due to their promising physicochemical properties, ease of modification, and ability to be coupled with several moieties and therapeutic molecules. They can not only be used as biocompatible nanocarriers to deliver therapeutic payloads to the tumor zone selectively but can also be combined with a variety of therapeutic modalities to achieve the desired treatments. This review comprehensively presented recent achievements and progress in COF-based cancer diagnosis, detection, and cancer therapy to provide a better prospect for further research. Herein our primary emphasis lies on exploring the application of COFs as potential sensors for cancer-derived biomarkers that have received comparatively less attention in previous discussions. While the utilization of COFs in solid tumor therapy has faced significant challenges in scientific research and clinical applications, we reviewed the most promising features that underscore their potential in cancer theranostics.

Hydrophilic Sulfonate Covalent Organic Frameworks for Serum Glycopeptide Profiling

Aberrant protein glycosylation is closely associated with a number of biological processes and diseases. However, characterizing the types of post-translational modifications (PTMs) from the complex biological samples is challenging for comprehensive glycoproteomic analysis. The development of high-performance enrichment materials and strategies during the sample pretreatment process is a prerequisite to glycoproteome research. Here in this work, a sulfonate-rich covalent organic framework (COF) called TpPa-(SO3H)2 (referred to as SCOF-2) was synthesized using the Schiff base reaction for the identification of glycopeptides. Benefiting from high hydrophilicity and abundant sulfonate affinity, a total of 28 and 16 glycopeptides could be efficiently detected from the standard glycoproteins of horseradish peroxidase (HRP) and immunoglobulin G (IgG) tryptic digest, respectively. Moreover, the as-prepared sulfonate-rich SCOF-2 has an ultralow detection limit (0.01 fmol μL-1), excellent enrichment selectivity (molar ratio HRP:BSA = 1:5000), satisfactory recovery rate (89.1%), high adsorption capacity (150 mg g-1) and good reusability in the individual enrichment. Meanwhile, by using the SCOF-2 adsorbent, 196 and 194 endogenous glycopeptides in the serum of ovarian cancer patients and healthy people among triplicates were successfully enriched and identified, respectively, using combined nanoLC-MS/MS technology. It demonstrated its great application potential in glycoproteomics research and provided a novel insight for the design of affinity materials.

Core-Shell Magnetic Particles: Tailored Synthesis and Applications

Core-shell magnetic particles consisting of magnetic core and functional shells have aroused widespread attention in multidisciplinary fields spanning chemistry, materials science, physics, biomedicine, and bioengineering due to their distinctive magnetic properties, tunable interface features, and elaborately designed compositions. In recent decades, various surface engineering strategies have been developed to endow them desired properties (e.g., surface hydrophilicity, roughness, acidity, target recognition) for efficient applications in catalysis, optical modulation, environmental remediation, biomedicine, etc. Moreover, precise control over the shell structure features like thickness, porosity, crystallinity and compositions including metal oxides, carbon, silica, polymers, and metal-organic frameworks (MOFs) has been developed as the major method to exploit new functional materials. In this review, we highlight the synthesis methods, regulating strategies, interface engineering, and applications of core-shell magnetic particles over the past half-century. The fundamental methodologies for controllable synthesis of core-shell magnetic materials with diverse organic, inorganic, or hybrid compositions, surface morphology, and interface property are thoroughly elucidated and summarized. In addition, the influences of the synthesis conditions on the physicochemical properties (e.g., dispersibility, stability, stimulus-responsiveness, and surface functionality) are also discussed to provide constructive insight and guidelines for designing core-shell magnetic particles in specific applications. The brand-new concept of "core-shell assembly chemistry" holds great application potential in bioimaging, diagnosis, micro/nanorobots, and smart catalysis. Finally, the remaining challenges, future research directions and new applications for the core-shell magnetic particles are predicted and proposed.

Glutathione-functionalized covalent organic frameworks@silica as a hydrophilic-hydrophobic balanced mixed-mode stationary phase for highly efficient separation of compounds with a wide range of polarity

BACKGROUND

Covalent organic frameworks (COFs) are a highly promising stationary phase for high-performance liquid chromatography (HPLC), but the separation of polar compounds is limited by their low hydrophilicity. Therefore, it is crucial to develop novel COFs-based stationary phases with balanced hydrophilicity-hydrophobicity for the efficient separation of different polar compounds.

RESULTS

In this paper, glutathione (GSH)-functionalized COFs@silica microspheres (GSH-COFs@SiO2) were synthesized via a two-step, post-synthesis modification strategy. The COFs particles was constructed onto silica surface by the covalent conjugation of 1,3,5-tris(4-aminophenyl)benzene and 2,5-divinylterephthalaldehyde. GSH containing abundant -NH2 and -COOH groups was bonded onto the surface of COFs@SiO2 to further enhance hydrophilicity. The resulting GSH-COFs@SiO2 exhibited balanced hydrophilicity-hydrophobicity and can be used in hydrophilic/reversed-phase liquid chromatography modes through multiple retention mechanisms. Consequently, a variety of compounds with different polarity, including nucleosides/bases, benzoic acids, anilines, phenols, alkylbenzenes and polycyclic aromatic hydrocarbons, were well separated with ideal resolution, satisfactory column efficiency and good peak shapes. Furthermore, this novel column exhibited remarkable column stability, as evidenced by intra-day relative standard deviations of 0.08 %-0.18 % for retention time and 0.45 %-1.47 % for peak area.

SIGNIFICANCE AND NOVELTY

This work demonstrates the superior hydrophilic-hydrophobic selectivity of GSH-COFs@SiO2 stationary phases towards compounds with a wide range of polarity and provides a very facile and easily popularized post-synthetic modification route for hydrophilic-hydrophobic balanced COFs-based HPLC stationary phases.

Optimization of glycopeptide enrichment techniques for the identification of clinical biomarkers

INTRODUCTION

The identification and characterization of glycopeptides through LC-MS/MS and advanced enrichment techniques are crucial for advancing clinical glycoproteomics, significantly impacting the discovery of disease biomarkers and therapeutic targets. Despite progress in enrichment methods like Lectin Affinity Chromatography (LAC), Hydrophilic Interaction Liquid Chromatography (HILIC), and Electrostatic Repulsion Hydrophilic Interaction Chromatography (ERLIC), issues with specificity, efficiency, and scalability remain, impeding thorough analysis of complex glycosylation patterns crucial for disease understanding.

AREAS COVERED

This review explores the current challenges and innovative solutions in glycopeptide enrichment and mass spectrometry analysis, highlighting the importance of novel materials and computational advances for improving sensitivity and specificity. It outlines the potential future directions of these technologies in clinical glycoproteomics, emphasizing their transformative impact on medical diagnostics and therapeutic strategies.

EXPERT OPINION

The application of innovative materials such as Metal-Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs), functional nanomaterials, and online enrichment shows promise in addressing challenges associated with glycoproteomics analysis by providing more selective and robust enrichment platforms. Moreover, the integration of artificial intelligence and machine learning is revolutionizing glycoproteomics by enhancing the processing and interpretation of extensive data from LC-MS/MS, boosting biomarker discovery, and improving predictive accuracy, thus supporting personalized medicine.

Covalent organic frameworks (COFs) as carrier for improved drug delivery and biosensing applications

Porous organic frameworks (POFs) represent a significant subclass of nanoporous materials in the field of materials science, offering exceptional characteristics for advanced applications. Covalent organic frameworks (COFs), as a novel and intriguing type of porous material, have garnered considerable attention due to their unique design capabilities, diverse nature, and wide-ranging applications. The unique structural features of COFs, such as high surface area, tuneable pore size, and chemical stability, render them highly attractive for various applications, including targeted and controlled drug release, as well as improving the sensitivity and selectivity of electrochemical biosensors. Therefore, it is crucial to comprehend the methods employed in creating COFs with specific properties that can be effectively utilized in biomedical applications. To address this indispensable fact, this review paper commences with a concise summary of the different methods and classifications utilized in synthesizing COFs. Second, it highlights the recent advancements in COFs for drug delivery, including drug carriers as well as the classification of drug delivery systems and biosensing, encompassing drugs, biomacromolecules, small biomolecules and the detection of biomarkers. While exploring the potential of COFs in the biomedical field, it is important to acknowledge the limitations that researchers may encounter, which could impact the practicality of their applications. Third, this paper concludes with a thought-provoking discussion that thoroughly addresses the challenges and opportunities associated with leveraging COFs for biomedical applications. This review paper aims to contribute to the scientific community's understanding of the immense potential of COFs in improving drug delivery systems and enhancing the performance of biosensors in biomedical applications.

Dual-ligand hydrogen-bonded organic framework: Tailored for mono-phosphopeptides and glycopeptides analysis

Hydrogen-bonded organic frameworks (HOFs) have emerged as a promising class of materials for applications of separation and enrichment. Utilizing multiple-ligands to construct HOFs is a promising avenue towards the development of structurally stable and functionally diverse frameworks, offering opportunities to create customized binding sites for selective recognition of biomolecules. In recent years, due to the crucial role that protein post-translational modifications (PTMs) play in maintaining protein function and regulating signaling pathways, and the growing recognition of the extensive cross-talk that can occur between PTMs, simultaneous analysis of different types of PTMs represents a requirement of a new generation of enrichment materials. Here, for the first attempt, we report a dual-ligand HOF constructed from borate anion and guanidinium cation for the simultaneous identification of glycopeptides and phosphopeptides, especially mono-phosphopeptides. According to theoretical calculations, the HOF functional sites display a synergistic "matching" effect with mono-phosphopeptides, resulting in a stronger enrichment effect for mono-phosphopeptides as compared to multi-phosphopeptides. Also, due to its high hydrophilicity and boronate affinity, this material can efficiently capture glycoproteins. HOF is set to become an active research direction in the development of highly efficient simultaneous protein enrichment materials, and offers a new approach for comprehensive PTMs analysis.

Designed Nanomaterials-Assisted Proteomics and Metabolomics Analysis for In Vitro Diagnosis

In vitro diagnosis (IVD) is pivotal in modern medicine, enabling early disease detection and treatment optimization. Omics technologies, particularly proteomics and metabolomics, offer profound insights into IVD. Despite its significance, omics analyses for IVD face challenges, including low analyte concentrations and the complexity of biological environments. In addition, the direct omics analysis by mass spectrometry (MS) is often hampered by issues like large sample volume requirements and poor ionization efficiency. Through manipulating their size, surface charge, and functionalization, as well as the nanoparticle-fluid incubation conditions, nanomaterials have emerged as a promising solution to extract biomolecules and enhance the desorption/ionization efficiency in MS detection. This review delves into the last five years of nanomaterial applications in omics, focusing on their role in the enrichment, separation, and ionization analysis of proteins and metabolites for IVD. It aims to provide a comprehensive update on nanomaterial design and application in omics, highlighting their potential to revolutionize IVD.

Magnetic chitosan hydrogel induces neuronal differentiation of neural stem cells by activating RAS-dependent signal cascade

Our aim was to modulate magnetic cues to influence the differentiation of neural stem cell (NSC) into neuron during nerve repair and to explore corresponding mechanisms. Here, a magnetic hydrogel composed of chitosan matrices and magnetic nanoparticles (MNPs) with different content was prepared as the magnetic-stimulation platform to apply intrinsically-present magnetic cue and externally-applied magnetic field to NSC grown on the hydrogel. The MNP content had regulatory effects on neuronal differentiation and the MNPs-50 samples exhibited the best neuronal potential and appropriate biocompatibility in vitro, as well as accelerated the subsequent neuronal regeneration in vivo. Remarkably, the use of proteomics analysis parsed the underlying mechanism of magnetic cue-mediated neuronal differentiation form the perspective of protein corona and intracellular signal transduction. The intrinsically-present magnetic cues in hydrogel contributed to the activation of intracellular RAS-dependent signal cascades, thus facilitating neuronal differentiation. Magnetic cue-dependent changes in NSCs benefited from the upregulation of adsorbed proteins related to "neuronal differentiation", "cell-cell interaction", "receptor", "protein activation cascade", and "protein kinase activity" in the protein corona. Additionally, magnetic hydrogel acted cooperatively with the exterior magnetic field, showing further improving neurogenesis. The findings clarified the mechanism for magnetic cue-mediated neuronal differentiation, coupling protein corona and intracellular signal transduction.

Composite materials based on covalent organic frameworks for multiple advanced applications

Covalent organic frameworks (COFs) stand for a class of emerging crystalline porous organic materials, which are ingeniously constructed with organic units through strong covalent bonds. Their excellent design capabilities, and uniform and tunable pore structure make them potential materials for various applications. With the continuous development of synthesis technique and nanoscience, COFs have been successfully combined with a variety of functional materials to form COFs-based composites with superior performance than individual components. This paper offers an overview of the development of different types of COFs-based composites reported so far, with particular focus on the applications of COFs-based composites. Moreover, the challenges and future development prospects of COFs-based composites are presented. We anticipate that the review will provide some inspiration for the further development of COFs-based composites.

Simultaneous detection of heterocyclic aromatic amines and acrylamide in thermally processed foods by magnetic solid-phase extraction combined with HPLC-MS/MS based on cysteine-functionalized covalent organic frameworks

Acrylamide (AA) and heterocyclic aromatic amines (HAAs), as classic hazards produced during food thermal processing, have been widely concerned, but because of their polarity difference, it is very difficult to detect these contaminants simultaneously. Herein, novel cysteine (Cys)-functionalized magnetic covalent organic frameworks (Fe₃O₄@COF@Cys) were synthesized via a thiol-ene click strategy and then used as adsorbents for magnetic solid-phase extraction (MSPE). Benefiting from the hydrophobic properties of COFs and the modification of hydrophilic Cys, AA and HAAs could be enriched simultaneously. Then, a rapid and reliable method based on MSPE coupled with HPLC-MS/MS was developed for the simultaneous detection of AA and 5 HAAs in thermally processed foods. The proposed method showed good linearity (R² ≥ 0.9987) with satisfactory limits of detection (0.012-0.210 μg kg^-1) and recoveries (90.4-102.8%). Actual sample analysis showed that the levels of AA and HAAs in French fries were affected by frying time and temperature, water activity of samples, content and type of reaction precursors, and reuse of oils.

An overview of the synthetic strategies of C3-symmetric polymeric materials containing benzene and triazine cores and their biomedical applications

C3-symmetric star-shaped materials are an emerging category of porous organic polymers with distinctive properties such as permanent porosity, good thermal and chemical stability, high surface area, and appropriate functionalization that promote outstanding potential in various applications. This review is mostly about constructing benzene or s-triazine rings as the center of C3-symmetric molecules and using side-arm reactions to add functions to these molecules. Over and above this, the performance of various polymerization processes has been additionally investigated in detail, including the trimerization of alkynes or aromatic nitriles, polycondensation of monomers with specific functional groups, and cross-coupling building blocks with benzene or triazine cores. Finally, the most recent progress in biomedical applications for C3-symmetric materials based on benzene or s-triazine have been summarized.

Super-hydrophilic sulfonate-modified covalent organic framework nanosheets for efficient separation and enrichment of glycopeptides

Highly efficient extraction of glycopeptides prior to mass spectrometry detection is extremely crucial for glycoproteomic research, especially in disease biomarker research. Reported here is the first time by applying two-dimensional (2D) covalent organic framework (COFs) nanosheets for highly efficient enrichment of glycopeptides. Particularly, by incorporating hydrophilic monomers through a bottom-up strategy, the 2D COF nanosheets (denoted as NUS-9) displayed an ultra-high graft density of sulfonic groups and super-hydrophilicity. In addition, because of the large surface area, low steric hindrance, high chemical stability, and abundant accessibility sites of 2D COF nanosheets, NUS-9 exhibited remarkable efficiency for glycopeptide enrichment, involving excellent detection sensitivity (0.01 fmol μL^-1), outstanding enrichment capability, and good enrichment selectivity (1:1500, horseradish peroxidase (HRP) tryptic digest to bovine serum albumin (BSA) tryptic digest), and recovery (92.2 ± 2.0%). Moreover, the NUS-9 was able to unambiguously detect 631 endogenous glycopeptides from human saliva, demonstrating an unparalleled high efficiency in glycopeptide enrichment. Gene ontology analyses of proteins from human saliva enriched by NUS-9 demonstrated its potential for comprehensive glycoproteome analysis.

Fabrication of a Magnetic Porous Organic Polymer for α-Glucosidase Immobilization and Its Application in Inhibitor Screening

The technology based on immobilized enzymes was employed to screen the constituents inhibiting disease-related enzyme activity from traditional Chinese medicine, which is expected to become an important approach of innovative drug development. Herein, the Fe₃O₄@POP composite with a core-shell structure was constructed for the first time with Fe₃O₄ magnetic nanoparticles as the core, 1,3,5-tris (4-aminophenyl) benzene (TAPB) and 2,5-divinylterephthalaldehyde (DVA) as organic monomers, and used as the support for immobilizing α-glucosidase. Fe₃O₄@POP was characterized by transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared, powder X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Fe₃O₄@POP exhibited a distinct core-shell structure and excellent magnetic response (45.2 emu g^-1). α-Glucosidase was covalently immobilized on core-shell Fe₃O₄@POP magnetic nanoparticles using glutaraldehyde as the cross-linking agent. The immobilized α-glucosidase possessed improved pH stability and thermal stability as well as good storage stability and reusability. More importantly, the immobilized enzyme exhibited a lower K_m value and enhanced affinity for the substrate than the free one. The immobilized α-glucosidase was subsequently used for inhibitor screening from 18 traditional Chinese medicines in combination with capillary electrophoresis analysis among which Rhodiola rosea exhibited the highest enzyme inhibitory activity. These positive results demonstrated that such magnetic POP-based core-shell nanoparticles were a promising carrier for enzyme immobilization and the screening strategy based on immobilized enzyme provided an effective way to rapidly explore the targeted active compounds from medicinal plants.

Construction of dual-hydrophilic metal-organic framework with hierarchical porous structure for efficient glycopeptide enrichment

As an important role in life activities, it is necessary and important to study protein glycosylation. The pre-enrichment of N-glycopeptides is a significant step in glycoproteomics research. According to the inherent size, hydrophilicity and other properties of N-glycopeptides, affinity materials designed to match them will be able to separate N-glycopeptides from complex samples. In this work, we designed and prepared dual-hydrophilic hierarchical porous metal-organic frameworks (MOFs) nanospheres by metal-organic assembly (MOA) based template method and post-synthesis modification strategy. The hierarchical porous structure significantly improved the diffusion rate and binding sites for N-glycopeptide enrichment. Furthermore, the combination of hydrophilic MOFs and small molecules endowed the as-prepared MOFs nanospheres excellent hydrophilicity, which is conducive to the enrichment of N-glycopeptides based on hydrophilic interaction liquid chromatography (HILIC). Therefore, the nanospheres showed surprising enrichment ability for N-glycopeptides such as excellent selectivity (1/500, human serum immunoglobulin G/bovine serum albumin, m/m) and extremely low detective limitation (0.5 fmol). Meanwhile, 550 N-glycopeptides were identified from rat liver samples, proving its application potential in glycoproteomics research and providing design idea for porous affinity materials.

Facile fabrication of hydrophilic covalent organic framework composites for highly selective enrichment of N-glycopeptides

The development of facilely synthetic materials acts an essential role in glycoproteome analysis, especially for the highly efficient enrichment of N-linked glycopeptides. In this work, a facile and timesaving route was introduced in which COF_TP-TAPT served as a carrier and poly (ethylenimine) (PEI) and carrageenan (Carr) were successively coated on the surface via electrostatic interaction. The resultant COF_TP-TAPT@PEI@Carr showed remarkable performance in glycopeptide enrichment with high sensitivity (2 fmol μL^-1), high selectivity (1:800, molar ratio of human serum IgG to BSA digests), large loading capacity (300 mg g^-1), satisfactory recovery (102.4 ± 6.0%) and reusability (at least eight times). Due to the brilliant hydrophilicity and electrostatic interactions between COF_TP-TAPT@PEI@Carr and positively charged glycopeptides, the prepared materials could be applied in the identification and analysis in the human plasma of healthy subjects and patients with nasopharyngeal carcinoma. As a result, 113 N-glycopeptides with 141 glycosylation sites corresponding to 59 proteins and 144 N-glycopeptides with 177 glycosylation sites corresponding to 67 proteins were enriched from 2 μL plasma trypsin digests of the control groups and patients with nasopharyngeal carcinoma, respectively. 22 glycopeptides were identified only from the normal controls and 53 glycopeptides were detected only from the other set. The results demonstrated that this hydrophilic material was promising on a large scale and further N-glycoproteome research.

Magnetic responsive hydroxyapatite scaffold modulated macrophage polarization through PPAR/JAK-STAT signaling and enhanced fatty acid metabolism

Despite the general observations of bone repair with magnetic cues, the mechanisms of magnetic cues in macrophage response during bone healing have not been systematically investigated. Herein, by introducing magnetic nanoparticles into hydroxyapatite scaffolds, an appropriate and timely transition from proinflammatory (M1) to anti-inflammatory (M2) macrophages during bone healing is achieved. The combined use of proteomics and genomics analysis reveals the underlying mechanism of magnetic cue-mediated macrophage polarization form the perspective of protein corona and intracellular signal transduction. Our results suggest that intrinsically-present magnetic cues in scaffold contribute to the upregulated peroxisome proliferator-activated receptor (PPAR) signals, and the activation of PPAR signal transduction in macrophages results in the downregulation of the Janus Kinase-Signal transducer and activator of transcription (JAK-STAT) signals and the enhancement of fatty acid metabolism, thus facilitating M2 polarization of macrophages. Magnetic cue-dependent changes in macrophage benefit from the upregulation of adsorbed proteins associated with "hormone" and "response to hormone", as well as the downregulation of adsorbed proteins related to "enzyme-linked receptor signaling" in the protein corona. In addition, magnetic scaffolds may also act cooperatively with the exterior magnetic field, showing further inhibition of M1-type polarization. This study demonstrates that magnetic cues play critical roles on M2 polarization, coupling protein corona, intracellular PPAR signals and metabolism.

Selective enrichment of glycopeptides using ground eggshell materials

The current research of protein glycosylation is focused on develop various functionalized hydrophilic materials that can effectively enrich glycopeptides. However, most of these materials require complex synthesis steps, plenty of chemical reagents, and high cost. In this study, we employed the natural eggshell for glycopeptides enrichment for the first time. Using horseradish peroxidase (HRP) tryptic digest as a standard sample, eggshell exhibited excellent sensitivity (0.05 fmol μL^-1), good selectivity [HRP tryptic digest:bovine serum albumin (BSA) tryptic digest = 1:1000], excellent size-exclusion effect (HRP tryptic digest:BSA protein = 1:10,000), good loading capacity (75 mg g^-1), and recovery (97.6 ± 0.3%). In addition, 153 and 114 glycopeptides were captured by eggshell from the serum tryptic digests of normal humans and diabetic patients, respectively. Benefiting from the singular porous structure and abundant biomass, eggshell performed excellently in the capture and separation of glycopeptides. These results demonstrated the potential of environmentally friendly eggshell in glycosylation proteomics analysis.

Covalent Organic Frameworks: Recent Progress in Biomedical Applications

Covalent organic frameworks (COFs) are a type of crystalline organic porous material with specific features and interesting structures, including porosity, large surface area, and biocompatibility. These features enable COFs to be considered as excellent candidates for applications in various fields. Recently, COFs have been widely demonstrated as promising materials for biomedical applications because of their excellent physicochemical properties and ultrathin structures. In this review, we cover the recent progress of COF materials for applications in photodynamic therapy, gene delivery, photothermal therapy, drug delivery, bioimaging, biosensing, and combined therapies. Moreover, the critical challenges and further perspectives with regards to COFs for future biology-facing applications are also discussed.

Recent advances in development of functional magnetic adsorbents for selective separation of proteins/peptides

Nowadays, proteins separation has attracted great attention in proteomics research. Because the proteins separation is helpful for making an early diagnosis of many diseases. Magnetic nanoparticles are an interesting and useful functional material, and have attracted extensive research interest during the past decades. Because of the excellent properties such as easy surface functionalization, tunable biocompatibility, high saturation magnetization etc, magnetic microspheres have been widely used in isolation of proteins/peptides. Notably, with the rapid development of surface decoration strategies, more and more functional magnetic adsorbents have been designed and fabricated to meet the growing demands of biological separation. In this review, we have collected recent information about magnetic adsorbents applications in selective separation of proteins/peptides. Furthermore, we present a comprehensive prospects and challenges in the field of protein separation relying on magnetic nanoparticles.

Advances in proteomics sample preparation and enrichment for phosphorylation and glycosylation analysis

As the common and significant chemical modifications, post-translational modifications (PTMs) play a key role in the functional proteome. Affected by the signal interference, low concentration, and insufficient ionization efficiency of impurities, the direct detection of PTMs by mass spectrometry (MS) still faces many challenges. Therefore, sample preparation and enrichment are an indispensable link before MS analysis of PTMs in proteomics. The rapid development of functionalized materials with diverse morphologies and compositions provides an avenue for sample preparation and enrichment for PTMs analysis. In this review, we summarize recent advances in the application of novel functionalized materials in sample preparation for phosphoproteomes and glycoproteomes analysis. In addition, this review specifically discusses the design and preparation of functionalized materials based on different enrichment mechanisms, and proposes research directions and potential challenges for proteomic PTMs research.

Covalent Organic Frameworks as Efficient Photoinitiators and Cross-Linkers To Fabricate Highly Stretchable Hydrogels

In this work, two kinds of imine-type covalent organic framework (COF) nanoparticles are demonstrated as efficient photocatalytic initiators to trigger the free-radical polymerization of acrylamide (AM) to prepare polyacrylamide (PAM) hydrogels under visible light irradiation, without any assistance from the co-initiator. Simultaneously, the COF nanoparticles bearing vinyl side groups (COF-V) promote covalent cross-linking of the polymer chains, which significantly reinforces the mechanical properties of the nanocomposite hydrogel. The obtained PAM/COF-V hydrogel is highly stretchable with an extraordinary elongation up to 3300% strain. On the other hand, the COF nanoparticles modified with methoxy moieties (COF-OMe) endow the resulting PAM/COF-OMe hydrogel with a promising fluorescence feature. In addition, this strategy provides a visible-light-regulated photocatalytic polymerization approach with a simplified recipe to fabricate COF-based nanocomposite hydrogels or resins with diverse functions.

Hydroxyl-riched covalent organic framework for solid-phase microextraction of flavonoids aglycones or their metabolites in mice's plasma: Luteolin and quercetagetin as examples

Herein, a hydroxyl‑riched covalent organic framework (named COF-DES-1) was synthesized using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dihydroxyterephthalaldehyde as building blocks and employed as a coating of solid-phase microextraction (SPME) fiber. Ascribed to the advantages (e.g. suitable pore size and rich functional group characteristics) of coating, the SPME fiber showed good adsorption capacities to flavonoids aglycones including luteolin and quercetagetin, and the maximum adsorption capacities for them were 145.31 µg and 84.75 µg, respectively. Due to the size exclusion property of COF-DES-1, SPME fiber showed good protein exclusion effects on seven selected proteins with high exclusion efficiencies (>93%). Accordingly, an attractive strategy of the combination of COF-DES-1 based SPME fiber and HPLC-MS/MS was proposed for the extraction and determination of luteolin, quercetagetin or their metabolites. The results revealed that the fiber can be effectively applied to extract luteolin and its metabolites, and quercetagetin from mice's palsma. Compared with the traditional protein precipitation methods, the extraction effects of SPME fiber based extraction method were much better, indicating the promising applicability of the fiber for the enrichment of flavonoids aglycones or their metabolites in biological samples.

Hydrophilic glutathione-modified flower-like hollow covalent organic frameworks for highly efficient capture of N-linked glycopeptides

Highly efficient enrichment of N-glycopeptides from complicated biosamples based on mass spectrometry is essential for biomedical applications, especially in disease biomarker research. In this work, glutathione (GSH)-modified hierarchical flower-like hollow covalent organic frameworks loaded with Au nanoparticles (HFH-COFs@Au@GSH) were synthesized for N-glycopeptide enrichment. Due to the abundant accessibility sites, high specific surface area, and inherent high stability of the hierarchical flower-like hollow structure, a large number of Au NPs and hydrophilic GSH can be modified on the HFH-COFs. The HFH-COFs@Au@GSH displayed excellent hydrophilicity and remarkable enrichment performance for N-glycopeptides: low detection limit (0.1 fmol μL^-1), large adsorption capacity (200 μg mg^-1), great selectivity (1 : 1000, HRP to BSA), and good reusability (at least 5 times). Furthermore, the HFH-COFs@Au@GSH were successfully applied to capture N-linked glycopeptides in human serum, and 308 N-glycosylation peptides corresponding to 84 N-glycosylation proteins with 123 N-glycosylation sites were detected. Gene ontology analyses were used to elucidate the cellular component, biological process and molecular function of detected glycoproteins in human serum, demonstrating the great potential of the HFH-COFs@Au@GSH in N-glycopeptide enrichment for glycoproteomic analysis of complex biological samples.

Recent advancements in glycoproteomic studies: Glycopeptide enrichment and derivatization, characterization of glycosylation in SARS CoV2, and interacting glycoproteins

Proteomics studies allow for the determination of the identity, amount, and interactions of proteins under specific conditions that allow the biological state of an organism to ultimately change. These conditions can be either beneficial or detrimental. Diseases are due to detrimental changes caused by either protein overexpression or underexpression caused by as a result of a mutation or posttranslational modifications (PTM), among other factors. Identification of disease biomarkers through proteomics can be potentially used as clinical information for diagnostics. Common biomarkers to look for include PTM. For example, aberrant glycosylation of proteins is a common marker and will be a focus of interest in this review. A common way to analyze glycoproteins is by glycoproteomics involving mass spectrometry. Due to factors such as micro- and macroheterogeneity which result in a lower abundance of each version of a glycoprotein, it is difficult to obtain meaningful results unless rigorous sample preparation procedures are in place. Microheterogeneity represents the diversity of glycans at a single site, whereas macroheterogeneity depicts glycosylation levels at each site of a protein. Enrichment and derivatization of glycopeptides help to overcome these limitations. Over the time range of 2016 to 2020, several methods have been proposed in the literature and have contributed to drastically improve the outcome of glycosylation analysis, as presented in the sampling surveyed in this review. As a current topic in 2020, glycoproteins carried by pathogens can also cause disease and this is seen with SARS CoV2, causing the COVID-19 pandemic. This review will discuss glycoproteomic studies of the spike glycoprotein and interacting proteins such as the ACE2 receptor.

Bi-amino acid functionalized biomimetic honeycomb chitosan membrane as a multifunctional hydrophilic probe for specific capture of N-linked glycopeptides in nasopharyngeal carcinoma's disease patient's serum

In this work, a novel porous bifunctionalized composite material was synthesized via a simple method. Gold nanoparticles are uniformly dispersed on the surface of the biomimetic honeycomb chitosan membrane through the interaction between amino and Au, and then cysteine and glutathione are successfully grafted onto the surface of the Au by the Au-S bond. The ingenious synergistic effect of cysteine and glutathione makes this bifunctionalized composite material have significant advantages of both superhydrophilicity and small steric hindrance. This material manifests excellent property in glycopeptides enrichment, with high selectivity (1:5000), low detection limit (0.1 fmol·μL^-1 ), high recovery rate (99.4 ± 0.5%) and good repeatability. In addition, with the help of nano-flow liquid chromatography tandem mass spectrometry, this composite achieved excellent performance in efficiently enriching glycopeptides in the serum of healthy people and nasopharyngeal carcinoma's disease patient. More excitingly, further gene ontology analysis of molecular function and biological process indicated that 41 original glycoproteins of the identified glycopeptides from serum of nasopharyngeal carcinoma's disease patient significantly partake in numerous cancer-associated events, including protease binding, calcium ion binding, enzyme binding, extracellular matrix organization, cellular response to tumor necrosis factor and inflammatory response. This article is protected by copyright. All rights reserved.

Hydrophilic magnetic covalent triazine frameworks for differential N-glycopeptides enrichment in breast cancer plasma membranes

Alterations in plasma membrane glycoproteins (PMGs) have been identified as a hallmark of cancer. The comparison and identification of differential PMGs is significant for finding new markers and understanding pathological processes. However, the research on PMGs is often constrained by the low abundance and the disturbance of abundant endogenous biomolecules during direct analysis. Here, we report a bottom-up strategy to enrich the PMGs of breast cancer cells using hydrophilic magnetic covalent triazine frameworks (CTFs). A total of 972 N-glycopeptides and 1006 N-glycosites belonging to 526 N-glycoproteins were enriched in MCF-10A plasma membrane tryptic digest by magnetic CTFs. And 680 N-glycopeptides and 806 N-glycosites belonging to 443 N-glycoproteins were enriched in SK-BR-3 plasma membrane tryptic digest. Furthermore, comparative analysis was performed based on gene ontology to verify breast cancer biomarkers (SUSD2 and ALCAM) and differential PMGs' function. This strategy which systematically integrates efficient enrichment of differential PMGs and in-depth comparative analysis has great potential for helping illuminate the atlas of breast cancer PMGs and the causes of tumor metastasis.

Functional Nanoparticles with Magnetic 3D Covalent Organic Framework for the Specific Recognition and Separation of Bovine Serum Albumin

Glutathione functionalized magnetic 3D covalent organic frameworks combined with molecularly imprinted polymer (magnetic 3D COF–GSH MIPs) were developed for the selective recognition and separation of bovine serum albumin (BSA). Ultrasonication was used to prepare magnetic 3D COFs with high porosity (~1 nm) and a large surface area (373 m² g⁻¹). The magnetic 3D COF–GSH MIP nanoparticles had an imprinting factor of 4.79, absorption capacity of 429 mg g⁻¹, magnetic susceptibility of 32 emu g⁻¹, and five adsorption–desorption cycles of stability. The proposed method has the advantages of a shorter equilibrium absorption time (1.5 h), higher magnetic susceptibility (32 emu g⁻¹), and larger imprinting factor (4.79) compared with those reported from other studies. The magnetic 3D COF–GSH MIPs used with BSA had selectivity factors of 3.68, 2.76, and 3.30 for lysozyme, ovalbumin, and cytochrome C, respectively. The successful recognition and separation of BSA in a real sample analysis verified the capability of the magnetic 3D COF–GSH MIP nanoparticles.

Glutathione-functionalized magnetic thioether-COFs for the simultaneous capture of urinary exosomes and enrichment of exosomal glycosylated and phosphorylated peptides

Exosomes play an irreplaceable role in physiological and pathological processes, and the study of proteomics (especially protein post-translational modifications, PTMs) in exosomes can reveal the pathogenesis of diseases and screen therapeutic disease targets. The separation and enrichment process is an essential step in mass spectroscopy-based exosomal PTMs studies to reduce sample complexity and ionization-suppression effects. Herein, we designed a novel magnetic zwitterionic material, namely glutathione-functionalized thioether covalent organic frameworks (Fe₃O₄@Thio-COF@Au@GSH), possessing fast magnetic responsiveness, regular porosity, and a suitable surface area. Thanks to the hydrophilicity and charge-switchable feature of GSH, for the first time, both the capture of exosomes from biological fluids and enrichment of the inherent glycoproteins/phosphoproteins in the exosomes were achieved with the same material. Furthermore, the high enrichment capacity was validated by theoretical calculations. The low detection limits (0.2/0.4 fmol for HRP/β-casein), high selectivity (1 : 1000 for HRP/β-casein : BSA molar ratio), and high exosomal glycoproteomics/phosphoproteomics profiling capability proved the feasibility of the developed method. This work provides a new heuristic strategy to solve the problems of exosomal capture and glycoproteins/phosphoproteins pretreatment in exosomal proteomics.

2D and 3D Covalent Organic Frameworks: Cutting-Edge Applications in Biomedical Sciences

Covalent organic frameworks (COFs) are crystalline porous organic structures with two- or three-dimensional (2D or 3D) features and composed of building blocks being connected via covalent bonds. The manifold applications of COFs in optoelectronic devices, energy conversion and storage, adsorption, separation, sensing, organocatalysis, photocatalysis, electrocatalytic reactions, and biomedicine are increasing because of their notable intrinsic features such as large surface area, porosity, designable structure, low density, crystallinity, biocompatibility, and high chemical stability. These properties have rendered 2D and 3D COF-based materials as desirable entities for drug delivery, gene delivery, photothermal therapy, photodynamic therapy, combination therapy, biosensing, bioimaging, and anticancer activities. Herein, different reactions and methods for the synthesis of 2D and 3D COFs are reviewed with special emphasis on the construction and state-of-the-art progress pertaining to the biomedical applications of 2D and 3D COFs of varying shapes, sizes, and structures. Specifically, stimuli-responsive COFs-based systems and targeted drug delivery approaches are summarized.

Surfactant-free synthesis of covalent organic framework nanospheres in water at room temperature

Covalent organic frameworks (COFs) are a new class of porous materials receiving much attention due to their unique characteristics. However, COFs have been usually synthesized under harsh and complicated conditions, limiting their practical applications. We propose a surfactant-free strategy to controllably synthesize an imine-based covalent organic framework (COF) nanomaterial in water at room temperature. Introduction of tiny amounts of co-solvents not only achieves the morphology and size control of COFs but also ensures stability of COF nanomaterials in aqueous solution. Moreover, water as a solvent plays an important role in the size adjustment of COFs. The surface area of the obtained COFs was approximately 398 m²/g with a pore size distribution of about 2.8 nm. In addition, the COFs displayed a good crystallinity.

Post-synthesis modification of covalent organic frameworks for ultrahigh enrichment of low-abundance glycopeptides from human saliva and serum

In this study, a novel type of covalent organic framework (COF) material rich in boronic acid sites was prepared through post-synthesis modification (TbBD@PEI@Au@4-MPBA). The surface of COF material had abundant carboxylic acid groups, which could bind a large amount of polyethyleneimine (PEI) through electrostatic interaction. At the same time, the amino groups on the PEI can be grafted with Au nanoparticles (Au NPs) in situ, and then 4-mercaptophenylboronic acid (4-MPBA) was modified by the reaction of Au and sulfhydryl groups. The massive grafting of boronic acid groups made the material's enrichment effect on glycopeptides expected. The results of experiments indicated that the composite material has high sensitivity (5 amol μL^-1) and selectivity (1:1000). In addition, the material has outstanding stability and reusability, with a load capacity of about 100 mg g^-1 and a recovery of 99.3 ± 2.2%. What's more, after enriched by TbBD@PEI@Au@4-MPBA, 56 endogenous glycopeptides from fresh human saliva were detected by MALDI-TOF MS, 56 unique glycopeptides corresponding to 31 glycoproteins from human saliva and 513 unique glycopeptides corresponding to 208 glycoproteins from serum of throat cancer patient were detected by nano-LC-MS/MS, respectively, which was expected to be applied to glycoproteomics research.

[Recent advances in functionalized magnetic nanomaterials for glycoprotein and glycopeptide enrichment]

Protein glycosylation is among the most common and important post-translational modifications, and plays an important regulatory role in many biological processes, including signal transduction, protein translation, and immune response. Abnormal protein glycosylation is also associated with numerous diseases, suggesting that glycoproteins may offer an array of useful disease biomarkers. Mass spectrometry (MS) has become an important analytical tool in glycoproteomics. However, the low abundance and weak ionization efficiency of glycopeptides have hindered direct mass spectrometric analyses, which remain considerably challenging. Glycoprotein and glycopeptide enrichment from complex biological samples is an important step in glycoproteomics. Diverse methods have recently been developed for specific glycoprotein and glycopeptide enrichment, including hydrophilic interaction liquid chromatography (HILIC), lectin affinity chromatography, boronate affinity chromatography, and hydrazide functional affinity chromatography. A variety of enrichment materials designed for the above strategies have been developed to meet the requirement of enriching low abundance glycoproteins and glycopeptides in complex samples. Magnetic solid phase extraction (MSPE) is an efficient sample pretreatment technology that offers advantages of simple operation, low cost, and high extraction efficiency. Functionalized magnetic nanomaterials have been widely used as adsorbents in glycoproteome studies. Since magnetic adsorbent is a key factor in MSPE, in this review, the preparation of magnetic nanomaterials functionalized with sugars, ionic liquids, lectins, boronate affinity ligands, metal organic frameworks, and covalent organic frameworks, and their applications in glycoprotein and glycopeptide enrichment are summarized. These functional magnetic nanomaterials possess high specific surface area and a large number of active adsorption sites, allowing different enrichment mechanisms, including HILIC, lectin affinity chromatography, and boronate and hydrazide functional affinity chromatography. These functional magnetic nanomaterials are mainly used to enrich glycoproteins and glycopeptides in serum, plasma, cells, tissues, saliva and other biological samples. Nearly 90 papers published in the last decade from the Science Citation Index (SCI) and Chinese core journals have been cited in this paper. Finally, the development and prospects of magnetic nanomaterials in glycoprotein and glycopeptide enrichment are also discussed.

[Covalent organic framework functional materials and their applications in glycopeptide enrichment]

蛋白质糖基化是生物体中最重要的翻译后修饰手段之一,糖蛋白/糖肽的有效分离和富集成为目前糖蛋白组学研究的首要问题。对于复杂的生物样本,糖蛋白的数量较少,酶解后大量高丰度非糖基化修饰肽的存在,使得低丰度糖肽的检测更加困难。因此,需要一些手段来有效地富集糖肽以提高其检测丰度,发展高选择性的糖肽富集材料及方法就成为在分子水平上有效地监测糖蛋白或糖肽的重要途径。相对于传统的糖肽富集材料,共价有机骨架材料具有比表面积大和可修饰位点丰富的优点,在糖肽富集领域具有很大的应用潜力。该文制备了一种新型的共价有机骨架材料(O-T-D-COFs),利用1,3,5-三(4-氨苯基)苯和2,5-二甲氧基苯-1,4-二甲醛作为反应单体通过共聚缩合反应生成的席夫碱构成了材料的框架,对合成后的中间体材料进行氧化处理,从而提高材料的富集性能。利用扫描电镜、透射电镜、红外光谱和固体核磁等表征技术对材料的结构进行了表征,并将其应用于糖肽的选择性富集。分别对富集过程的上样条件、淋洗条件、洗脱条件进行了优化,结合质谱检测技术,从人血清免疫球蛋白G酶解液中观察到32个明显的糖肽信号峰。通过模拟复杂样本体系验证材料富集选择性,在人血清免疫球蛋白G和牛血清白蛋白的酶解液混合物摩尔比达到1∶50时,该材料仍然保持了良好的选择性。此外,还考察了材料的检测限、富集容量、回收率等富集性能,及在实际样品中的应用潜力。以人血清免疫球蛋白G为评价对象,O-T-D-COFs具有较低的检测限(2.5 fmol/μL)、较高的富集容量(120 mg/g),及较好的富集回收率(103.5%±6.6%、101.5%±10.4%)。在血清样品中富集到来自53个N-糖蛋白中的86个N-糖肽序列,并鉴定到了94个N-糖基化位点。这些结果都表明,该材料在糖肽富集领域有较好的应用前景。

Construction of a magnetic covalent organic framework with synergistic affinity strategy for enhanced glycopeptide enrichment

Considering the inherent properties of glycopeptides, such as glycan structure, size, and hydrophilicity, affinity materials possessing suitable functional molecule-glycan interactions, matched channels with size exclusion, and surfaces with hydrophilic interactions are preferred for glycopeptide separation in biological samples. Here, a novel boronic-acid-functionalized magnetic covalent organic framework was prepared through epitaxial growth and multi-ligand strategies. The multi-ligand strategy was firstly employed to prepare functionalized magnetic covalent organic framework without any post-functionalization protocol. Notably, the proposed strategy was found to be time saving, robust, and reproducible. The versatile magnetic covalent organic framework nanocomposite was endowed with phenylboronic acid functional molecules, strong hydrophilic features, mesoporous channels, fast magnetic responsiveness, and a large surface area. Benefitting from multiple affinity interactions, namely, synergistic reversible covalent interactions and hydrophilic affinity interactions, the nanocomposite presented extremely high performance in the recognition of intact N-glycopeptides. The inherent properties endowed the nanocomposite with excellent enrichment performance for N-glycopeptides: excellent selectivity (1 : 2000, IgG/BSA, m/m), an ultralow detection limit (0.05 fmol μL^-1), and a good size-exclusion effect (1 : 500, IgG digests/BSA, m/m). More excitingly, a total of 1921 unique intact glycopeptides assigned to 1154 glycoproteins were identified from rat liver tissue; this performance is superior to that of commercial products. Additionally, the nanocomposite was successfully applied to enrich intact glycopeptides of exosomes extracted from healthy individuals and renal failure patients, providing a novel concept for the design of materials using a synergistic affinity strategy for sample preparation in glycoproteomics.

Bowl-like mesoporous polydopamine with size exclusion for highly selective recognition of endogenous glycopeptides

It has been confirmed that endogenous glycopeptide plays an important role in a variety of pathological and physiological processes. However, direct analysis of endogenous glycopeptide is still a great challenge owing to the low abundance of endogenous glycopeptides and the presence of a large number of interfering substances such as large-sized proteins and heteropeptides in complex biological sample. Herein, we reported a novel bowl-like mesoporous polydopamine nanoparticle modified by carrageenan (denoted as MPDA@PEI@CA) with strong hydrophilicity and size-exclusion effect for high specificity enrichment of endogenous glycopeptides. Thanks to the suitable pore channel structure as well as strong hydrophilic surface, the as-prepared MPDA@PEI@CA nanoparticles exhibited prominent performance in enrichment of N-linked glycopeptide with ultrahigh selectivity (1:5000 M ratio of horseradish peroxidase (HRP) digests/bovine serum albumin (BSA) digests), low detection limit (5 fmol μL^-1), outstanding size-exclusion ability (1:1000 mass of HRP/BSA), and unique reusability (five times). 125 N-glycosylation sites of 134 glycopeptides from 65 glycoproteins were identified from 2 μL sample of human serum treated with the MPDA@PEI@CA nanoparticles, which manifested the ability to enrich endogenous N-linked glycopeptides from complex biological samples. These results indicated that the bowl-like MPDA@PEI@CA nanoparticles with novel structure prepared in this work had great potential for glycopeptidome analysis.

Hollow MnFe2O4@C@APBA Nanospheres with Size Exclusion and pH Response for Efficient Enrichment of Endogenous Glycopeptides

Enrichment and detection of glycopeptides are an important clinical measure for the diagnosis of complex diseases. Enrichment materials play a key role in this process; they must have an effective sample-screening ability to eliminate the interference of nonglycopeptides. In this work, novel hollow MnFe₂O₄@C@APBA nanospheres (HMCAs) with magnetic and pH responsiveness were prepared for glycopeptide enrichment. The as-prepared composites have a suitable hollow structure and large specific surface area, and the boron hydroxyl group in their cavities can fix or disconnect the hydrophilic groups of the glycopeptides at different pH, so the glycopeptides can be adsorbed or desorbed in a controllable way. Enrichment results showed that the HMCAs exhibited an excellent enrichment performance: ultralow limit of detection (approximately 0.5 fmol μL^-1), perfect size-exclusion effect (HRP/BSA, 1:800, w/w), favorable universality (HRP, IgG, and RNase B), and high binding capacity (150 mg/g). In order to verify the application of materials in practice, the HMCAs were used for the analysis of complex samples and it was found that 474 glycopeptides were identified from 210 glycoproteins in three replicate analyses of 2 μL of human serum. The results showed that the HMCAs could be used as a promising enrichment material for glycopeptide characterization in MS-based glycoproteomics and related fields.

Gold nanoparticle-glutathione functionalized MOFs as hydrophilic materials for the selective enrichment of glycopeptides

Herein, a novel zwitterionic hydrophilic metal-organic framework (MOF)-functionalized material was synthesized through grafting l-glutathione (GSH) onto the Au which acts as the intermediate layer to modify the base material (PEI-ZIF-8) by the sulfhydryl group provided by GSH and the affinity provided by Au (denoted as PEI-ZIF-8@Au@GSH). The obtained product was employed to capture glycopeptides. Benefit from its excellent hydrophilic properties, abundant amphoteric ions, and unique large specific surface area, this material demonstrated amazing ability in the enrichment and identification of glycopeptides. As a result, the PEI-ZIF-8@Au@GSH displayed high sensitivity (as low as 2 fmol), excellent binding capacity (500 mg/g), outstanding enrichment selectivity (maximum mass ratio HRP to BSA is 1:1000) toward glycopeptides, and the ability to recycle at least five times. Furthermore, 35 and 51 glycopeptides were successfully detected from 5 μL human saliva and human serum respectively in the examination of the actual sample by MALDI-TOF MS. The above results indicated that the PEI-ZIF-8@Au@GSH had a satisfactory potential in the field of glycoproteomics.

Intermolecular B-N coordination and multi-interaction synergism induced selective glycoprotein adsorption by phenylboronic acid-functionalized magnetic composites under acidic and neutral conditions

Abnormal protein glycosylation is associated with many diseases including cardiovascular disease, diabetes, and cancer. Therefore, selective capturing of glycoproteins under physiological or weak acid conditions (tumor microenvironment) is vital for disease diagnosis and further comprehensive analysis. Here, we propose a strategy of intermolecular B-N bond-based phenylboronic acid affinity to capture glycoproteins under neutral and slightly acidic conditions. Surprisingly, the captured glycoproteins were released in alkaline solution. This is contrary to the traditional phenylboric acid affinity, and we studied this from the perspective of materials, proteins, and incubation conditions. We identified the synergistic effect of intermolecular B-N bond-based phenylboronic acid affinity, electrostatic interaction, and polymer brush structure-based glycoprotein adsorption under slightly acidic conditions. The electrostatic repulsion between Fe3O4@SiO2@poly (2-aminoethyl methacrylate hydrochloride)-4-carboxyphenylboronic acid (Fe3O4@SiO2@PAMA-CPBA) nanoparticles and transferrin (TRF) was far greater than the specific binding between phenylboric acid of CPBA and glycosylation residues of TRF resulting in the release of the captured glycoproteins in alkaline solution. Fe3O4@SiO2@PAMA-CPBA nanoparticles exhibited different selectivity capabilities toward different glycoproteins in multiprotein solutions due to protein interactions. These results may pave a new way for the design of phenylboric acid-based materials towards glycoprotein adsorption in a physiological environment.