Post-synthetic modification of an amino-functionalized metal-organic framework for highly efficient enrichment of N-linked glycopeptides

High-sensitivity detection of glycoproteins by high-density boric acid modified metal-organic framework surface molecularly imprinted polymers resonant light scattering sensor

Glycoproteins are difficult to be detected by imprinting strategy due to their low natural abundance, high flexible conformation and large size. Herein, a high-density boric acid modified metal-organic framework (MOF) surface molecularly imprinted polymer (SMIP) resonant light scattering sensor was constructed for the high-sensitivity detection of target glycoproteins. A MOF with large specific surface area was selected as the substrate material to support the boric acid group with high loading density (4.66 %). The introduction of the boric acid group in the SMIP provided a high-affinity binding site for the recognition and binding of glycoproteins. Shallow surface cavities with rapid mass transfer (equilibrium time 20 min) were thus formed by surface imprinting. Furthermore, high sensitivity (limit of detection 15 pM) was achieved at physiological pH (7.4), which was conducive to the detection of glycoproteins with low natural abundance in complex biological samples and maintaining physiological activity.

A review of intact glycopeptide enrichment and glycan separation through hydrophilic interaction liquid chromatography stationary phase materials

Protein glycosylation, one of the most important biologically relevant post-translational modifications for biomarker discovery, faces analytical challenges due to heterogeneous glycosite, diverse glycans, and mass spectrometry limitations. Glycopeptide enrichment by removing abundant hydrophobic peptides helps overcome some of these obstacles. Hydrophilic interaction liquid chromatography (HILIC), known for its selectivity, glycan separations, intact glycopeptide enrichment, and compatibility with mass spectrometry, has seen recent advancements in stationary phases like Amide-80, glycoHILIC, amino acids or peptides for improved HILIC-based glycopeptide analysis. Utilization of these materials can improve glycopeptide enrichment through solid-phase extraction and separation via high-performance liquid chromatography. Additionally, using glycopeptides themselves to modify HILIC stationary phases holds promise for improving selectivity and sensitivity in glycosylation analysis. Additionally, HILIC has capability to assess the information about glycosites and structural information of glycans. This review summarizes recent breakthroughs in HILIC stationary materials, highlighting their impact on glycopeptide analysis. Ongoing research on advanced materials continues to refine HILIC's performance, solidifying its value as a tool for exploring protein glycosylation.

From Nanozymes to Multi-Purpose Nanomaterials: The Potential of Metal-Organic Frameworks for Proteomics Applications

Metal-organic frameworks (MOFs) have the potential to revolutionize the biotechnological and medical landscapes due to their easily tunable crystalline porous structure. Herein, the study presents MOFs' potential impact on proteomics, unveiling the diverse roles MOFs can play to boost it. Although MOFs are excellent catalysts in other scientific disciplines, their role as catalysts in proteomics applications remains largely underexplored, despite protein cleavage being of crucial importance in proteomics protocols. Additionally, the study discusses evolving MOF materials that are tailored for proteomics, showcasing their structural diversity and functional advantages compared to other types of materials used for similar applications. MOFs can be developed to seamlessly integrate into proteomics workflows due to their tunable features, contributing to protein separation, peptide enrichment, and ionization for mass spectrometry. This review is meant as a guide to help bridge the gap between material scientists, engineers, and MOF chemists and on the other side researchers in biology or bioinformatics working in proteomics.

Recent advance on microextraction sampling technologies for bioanalysis

The contents of target substances in biological samples are usually at low concentration levels, and the matrix of biological samples is usually complex. Sample preparation is considered a very critical step in bioanalysis. At present, the utilization of microextraction sampling technology has gained considerable prevalence in the realm of biological analysis. The key developments in this field focus on the efficient microextraction media and the miniaturization and automation of adaptable sample preparation methods currently. In this review, the recent progress on the microextraction sampling technologies for bioanalysis has been introduced from point of view of the preparation of microextraction media and the microextraction sampling strategies. The advance on the microextraction media was reviewed in detail, mainly including the aptamer-functionalized materials, molecularly imprinted polymers, carbon-based materials, metal-organic frameworks, covalent organic frameworks, etc. The advance on the microextraction sampling technologies was summarized mainly based on in-vivo sampling, in-vitro sampling and microdialysis technologies. Moreover, the current challenges and perspective on the future trends of microextraction sampling technologies for bioanalysis were briefly discussed.

Oriented assembly of hydrophilic nanochains modified by porous zirconium-based coordination polymers for glycopeptides analysis

Mass spectrometry (MS)-based glycoproteomics research requires additional sample pretreatment to improve the effective identification of low-abundance glycopeptides without interference from non-glycoproteins. Herein, an attractive strategy using resorcinol-formaldehyde (RF) resin and zirconium-based coordination polymer (Zr-BCP) was established to prepare one-dimensional porous coordination polymer composites for glycopeptide enrichment before MS analysis. The obtained Fe3O4@RF@Zr-BCP nanochains feature excellent magnetic response (42.26 emu/g), high hydrophilicity (16.0°), and large specific surface area (140.84 m2/g), which provides abundant affinity sites for specific capture of glycopeptides. The materials exhibit outstanding performance in the enrichment of glycopeptides in terms of sensitivity (15 fmol/μL IgG), selectivity (1:200, molar ratio of IgG/BSA), loading capacity (200 mg/g) and recovery (106.4 ± 3.5%). In addition, the developed method based on Fe3O4@RF@Zr-BCP has been successfully applied to capture glycopeptides in tryptic digest of mouse teratoma cell extracts. It is worth emphasizing that compared with dispersed nanoparticles, the one-dimensional chain structure brings extraordinary reusability to Fe3O4@RF@Zr-BCP nanochains, which is conducive to the rapid cyclic enrichment of glycopeptides. This present work provides a potential enrichment platform for comprehensive glycoprotein analysis, and opens a new avenue for the application of oriented-assembly nanochains.

Water-stable hydrophilic metal organic framework composite for the recognition of N-glycopeptides during diabetes progression by mass spectrometry

A hydrophilic Al-MOFs composite was prepared using cheap and available reagents in water via a suitable large-scale production, an economical and environment-friendly method for capturing N-glycopeptides. The prepared Al-MOFs composite with high hydrolytically stable and hydrophilic 1D channels exhibits an ultralow detection limit (0.5 fmol/μL), and excellent reusability (at least 10 cycles) in the capture of N-glycopeptides from standard bio-samples. Interestingly, the Al-MOFs composite also shows remarkable performance in practical applications, where 300 N-glycopeptides ascribed to 124 glycoproteins were identified in 1 µL human serum and were successfully applied in profiling the differences of N-glycopeptides during diabetes progression. Moreover, 12 specific glycoproteins used as biomarkers to accurately distinguish the progression of diabetes are identified. The present work provides a potential commercial method for large-scale glycoproteomics research in complex clinical samples while offering new guidance for the precise diagnosis of diabetes progression.

Advances in hydrophilic metal-organic frameworks for N-linked glycopeptide enrichment

The comprehensive profiling of glycoproteins is of great significance for the timely clinical diagnosis and therapy. However, inherent obstacles hamper their direct analysis from biological samples, and specific enrichment prior to analysis is indispensable. Among the various approaches for glycopeptide enrichment, hydrophilic interaction liquid chromatography (HILIC) has attracted special focus, especially for the development of novel hydrophilic materials, which is the key of HILIC. Metal-organic frameworks (MOFs) are a type of porous materials constructed from the self-assembly of metal and organic linkers. Advantages such as high surface area, flexible pore size, and easy modification render hydrophilic MOFs as ideal candidates for HILIC, which has inspired many studies over the past years. In this review, advances in hydrophilic MOFs for N-linked glycopeptide enrichment are summarized. According to the synthesis strategies, those materials are categorized into three classes, namely pristine MOFs, MOFs with chemical modifications, and MOFs-derived composite. In each categorization, the preparation and the function of different moieties are covered, as well as the enrichment performances of sensitivity, selectivity, and practical application. Finally, a summary and future perspective on the applications of hydrophilic MOFs for N-linked glycopeptide enrichment are briefly discussed. This review is expected to raise awareness of the properties of hydrophilic MOFs and offer some valuable information to further research in glycoproteomics.

Construction of boric acid-functionalized metal-organic frameworks for glycopeptide recognition in the serum of cervical cancer patients

RATIONALE

Cervical cancer is one of the most common malignant tumors in women, and it is essential to explore potential biomarkers such as glycopeptides closely related to cancer in physiological samples of cervical cancer patients. Sample pretreatment is required before direct detection using mass spectrometry because there are certain limitations. Meanwhile, it is still highly desired to promote the functionalization and application of metal-organic framework (MOF)-derived materials.

METHODS

Using a post-synthesis modification method, a novel type of boric acid-functionalized MOF probe (designated as UiO-66@PEI@Au@B(OH)₂ ) is prepared for recognition of glycopeptides. The results are obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-liquid chromarography-tandem mass spectrometry.

RESULTS

The UiO-66@PEI@Au@B(OH)₂ probe exhibits a low detection limit (0.6 fmol μL^-1 ), an excellent recovery rate, comparatively good reusability and selectivity (HRP digests:BSA digests = 1:500). When UiO-66@PEI@Au@B(OH)₂ is used to selectively capture glycopeptides from the serum of a healthy person and a cervical cancer patient, 101 glycopeptides corresponding to 54 glycoproteins and 108 glycopeptides corresponding to 57 glycoproteins are detected, respectively.

CONCLUSIONS

The successful preparation of UiO-66@PEI@Au@B(OH)₂ provides a path for the investigation of the functionalization of MOF-derived materials. The excellent performance of UiO-66@PEI@Au@B(OH)₂ not only demonstrates the huge potential of functionalized MOFs in the glycoproteome, but also opens up new phases of the application of MOF-based materials.

Maltose-functional metal-organic framework assisted laser desorption/ionization mass spectrometry for small biomolecule determination

A series of functional metal-organic frameworks (MOFs) were facilely prepared through an one-pot procedure or post-synthetic modification strategy and used as matrices in laser desorption ionization mass spectrometry (LDI-MS). Compared with traditional organic matrices and other MOFs, maltose-functional MOF MIL-101-maltose demonstrated ultrahigh ionization efficiency, free matrix background, uniform crystallization, and good dispersibility. A simple, general, and efficient LDI-MS platform was developed for rapid detection of various small biomolecules using MIL-101-maltose as matrix, providing several advantages including low sample consumption of 500 nL, short analysis time of few seconds, strong salt tolerance (500 mM NaCl), and satisfactory reproducibility. The MIL-101-maltose matrix was used for serum glucose determination and successfully distinguished the diabetic patients from the healthy controls. This work provides a generic LDI-MS platform for fast determination of small biomolecules with high potential in clinical diagnosis and disease monitoring.

A novel hydrophilic MOFs-303-functionalized magnetic probe for the highly efficient analysis of N-linked glycopeptides

The effective analysis of glycoproteomics in clinical complex samples is of vital importance for the diagnosis and therapy of diseases. In this study, a hydrophilic MOFs-303-functionalized magnetic probe (GO@Fe₃O₄@MOF-303) is designed and fabricated to profile N-linked glycopeptides. Owing to its strong magnetic property, large surface area (845 m² g^-1), excellent hydrophilicity and suitable porous structure, the GO@Fe₃O₄@MOF-303 probe exhibits an ultralow detection limit (0.1 fmol μL^-1), perfect size-exclusion effect (HRP digests/BSA protein/HRP protein, 1 : 1000 : 1000, w/w/w), a high binding capacity (200 mg g^-1) and excellent reusability in the capture of standard N-linked glycopeptides. More excitingly, the GO@Fe₃O₄@MOF-303 probe also shows remarkable performance in practical applications, where 274 N-linked glycopeptides from 101 glycoproteins were identified in total for healthy controls, while a total of 265 N-linked glycopeptides from 102 glycoproteins were identified in serum (1 μL) with hepatocellular carcinoma (HCC). In addition, we discovered 4 up-regulated and 19 down-regulated serum glycoproteins in HCC patients by the hierarchical clustering heatmap. All results demonstrated that the reusable GO@Fe₃O₄@MOF-303 probe has great potential in profiling different N-linked glycopeptides in complex clinical samples. This study not only developed a novel probe for the highly effective capture of N-linked glycopeptides but also contributed to further understanding the mechanism of HCC and provides guidance for the development of novel clinical diagnostic methods.

Enrichment of diamide insecticides from environmental water samples using metal-organic frameworks as adsorbents for determination by liquid chromatography tandem mass spectrometry

A series of metal-organic frameworks composed of different metal ions and organic linkers were facilely synthesized and used as adsorbents for five diamide insecticides for the first time. Among them, MIL-101-NH₂ performed much better than other materials due to extraordinarily high specific surface area, strong water stability, specific interaction with analytes. A sensitive method was developed with MIL-101-NH₂ based dispersive solid phase extraction combining with liquid chromatography tandem mass spectrometry (dSPE-LC-MS/MS). Important parameters including adsorbent amount, enrichment time, elution solvent and volume, pH and salt effect were investigated to achieve the best enrichment efficiency. At selected conditions, the proposed method showed ultrahigh sensitivity with limits of detection low to 0.01-0.03 ng/mL, which was 2-3 orders of magnitude lower than reported methods. Wide linearity in the range of 0.03-1000 ng/mL (chlorantraniliprole, cyantraniliprole) and 0.1-2000 ng/mL (flubendiamide, cyclaniliprole, tetrachlorantraniliprole) were established with satisfactory coefficient of determination. The method was successfully used for analyzing of diamide insecticides in environmental water samples and flubendiamide was detected in several samples. This work demonstrated the first example of developing novel nanomaterials in trace amount diamide insecticide enrichment from practical samples, which opens a new perspective in establishing nanomaterial-based sample preparation method for diamide insecticide analysis.

Functionalization of Mono- and Bimetallic MIL-100(Al,Fe) MOFs by Ethylenediamine: Postfunctionalization, Brønsted Acido-Basicity, and Unusual CO2 Sorption Behavior

The metal sites of MIL-100(Fe), MIL-100(Fe,Al), and MIL-100(Al) metal-organic frameworks (MOFs) were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierarchized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule in each trimeric Al₃O cluster unit, whereas the other two aluminum sites are occupied by a hydroxyl and a water molecule. The -NH₂ sites of the grafted ethylenediamine can be used for further postfunctionalization through amine chemistry and are responsible for the basicity of the functionalized material as well as increased affinity for CO₂. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity. Finally, the Al-containing MOFs show an unusual carbon dioxide sorption mechanism at high pressures that distinguishes those materials from their iron and chromium counterparts and is suspected to be due to the presence of polarized Al-OH bonds.

Sensitive and selective detection of chromium (VI) based on two-dimensional luminescence metal organic framework nanosheets via the mechanism integrating chemical oxidation-reduction and inner filter effect

Two-dimensional luminescence metal organic framework nanosheets (LMOF) named NH₂-CuMOFs were synthesized using Cu (II) nodes coordinated with negatively charged 2-aminoterephthalic acid (NH₂-BDC) via a bottom-up strategy, which were first used as the fluorescent probes for the detection of chromium Cr (VI). The nanosheets possess stable fluorescence with the maximum emission wavelength of 436 nm at excitation of 338 nm that can be effectively quenched by hexavalent chromium Cr (VI). The NH₂-CuMOFs nanosheets show superior advantage over the linker of NH₂-BDC for the excellent selectivity to Cr (Ⅵ) without the interferences of other metal ions. The mechanism investigation suggested that the sensitive detection of Cr (VI) was attributed to the chemical oxidation-reduction (redox) reaction and internal filtration effect (IFE) between Cr (VI) and NH₂-CuMOFs nanosheets. Based on this mechanism, the quantitation of Cr (VI) was realized in the linear range of 0.1-20 μM with a detection limit of 18 nM. Moreover, the detection of Cr (VI) in real samples was also conducted with good recovery. This work provides an optical sensing nanoplatform for heavy metal ions based on two-dimensional LMOFs via a novel mechanism integrating chemical redox reaction and IFE, which may promise broad application prospect for two-dimensional luminescence nanosheets.

Engineering of nanomaterials for mass spectrometry analysis of biomolecules

Mass spectrometry (MS) based analysis has received intense attention in diverse biological fields. However, direct MS interrogation of target biomolecules in complex biological samples is still challenging, due to the extremely low abundance and poor ionization potency of target biological species. Innovations in nanomaterials create new auxiliary tools for deep and comprehensive MS characterization of biomolecules. More recently, growing research interest has been directed to the compositional and structural engineering of nanomaterials for enriching target biomolecules prior to MS analysis, enhancing the ionization efficiency in MS detection and designing biosensing nanoprobes in sensitive MS readout. In this review, we mainly focus on the recent advances in the engineering of nanomaterials towards their applications in sample pre-treatment, desorption/ionization matrices and ion signal amplification for MS profiling of biomolecules. This review will provide a toolbox of nanomaterials for researchers devoted to developing analytical methods and practical applications in the biological MS field.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. 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. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Enzymatic Hydrolysis-Responsive Supramolecular Hydrogels Composed of Maltose-Coupled Amphiphilic Ureas

Maltose is a ubiquitous disaccharide produced by the hydrolysis of starch. Amphiphilic ureas bearing hydrophilic maltose moiety were synthesized via the following three steps: I) construction of urea derivatives by the condensation of 4-nitrophenyl isocyanate and alkylamines, II) reduction of the nitro group by hydrogenation, and III) an aminoglycosylation reaction of the amino group and the unprotected maltose. These amphiphilic ureas functioned as low molecular weight hydrogelators, and the mixtures of the amphipathic ureas and water formed supramolecular hydrogels. The gelation ability largely depended on the chain length of the alkyl group of the amphiphilic urea; amphipathic urea having a decyl group had the highest gelation ability (minimum gelation concentration=0.4 mM). The physical properties of the supramolecular hydrogels were evaluated by measuring their thermal stability and dynamic viscoelasticity. These supramolecular hydrogels underwent gel-to-sol phase transition upon the addition of α-glucosidase as a result of the α-glucosidase-catalyzed hydrolysis of the maltose moiety of the amphipathic urea.

Bioinspired dandelion-like silica nanoparticles modified with L-glutathione for highly efficient enrichment of N-glycopeptides in biological samples

The pretreatment of complicated biological samples to eliminate the interference of nonglycopeptides and improve the efficiency of glycopeptides detection is crucial in glycoproteomics research. Hydrophilic interaction chromatography (HILIC) has been adopted for enrichment of glycosylated peptides following identification with mass spectrometry, but it is still urgent to develop novel hydrophilic materials to save cost and improve enrichment efficiency. Scientists are pursuing to fabricate freestanding intelligent artificial materials. One promising approach is to use biomimic material. In our case, "one-pot" strategy was developed to prepare bioinspired nano-core-shell silica microspheres (CSSMs), employing tetrapropylorthosilicate as the silicon source and phenolic resin as the soft template. The pore structure of the obtained microspheres diverged from the center to the outside with diameter ranged from 150 to 340 nm, and shell layer ranged from 25 to 83 nm by adjusting the preparation parameters. Some of them showed dandelion-like morphology. After hydrophilic modification, these CSSMs exhibited great hydrophilicity and could be used as sorbents for enriching N-glycopeptides from complicated biological samples in HILIC. Up to 594 unique N-glycopeptides and 367 N-glycosylation sites from 182 N-glycoproteins were unambiguously identified from 2 μL of human serum, which was superior to the enrichment performance of many HILIC materials in reported papers, demonstrating great potential advantages in proteomic application.

Regulating metal-organic frameworks as stationary phases and absorbents for analytical separations

Metal-organic frameworks (MOFs) are highly ordered framework systems composed of metal centers and organic linkers formed through coordination bonds. The diversity of metal elements and easily modified organic ligands, together with controllable synthetic approaches, gives rise to the designability of various MOF structures and topologies and the capability of MOFs to be functionalized. Their structural diversity provides MOFs with many unique properties, such as permanent porosity, flexible structures, thermostability, and high adsorption capacity, leading to great practicability in technical applications. In this review, we concentrate on the applications of MOFs in the field of gas chromatography, high-performance liquid chromatography, and the enrichment of biomolecules, based on rational arrangements in the structures and functions of MOFs. Moreover, we emphasize the importance of structural and chemical regulations for the improvement of separation efficiency.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

Tailoring the Surface Properties of Co-based Metal-Organic Frameworks for Highly Efficient and Selective Enrichment of Immunoglobulin G

The high tunability of metal-organic frameworks (MOFs) provides attractive flexibility to tailor their surface properties for practical demands. Here we report the regulation of the surface properties (hydrophilicity and charge characteristics) of Co-based MOFs by exploiting different organic building units and tailor them as efficient adsorbents for specific protein enrichment. Compared with the pristine Co-based MOF (Co-MOF) and the aminated MOF (Co-MOF-NH₂), the MOF decorated with abundant hydroxyl groups (Co-MOF-OH) exhibits superior adsorption selectivity and enriched efficiency toward immunoglobulin G (IgG) in the physiological state (pH 7.4) by taking advantage of the favorable hydrogen-bonding interactions and electrostatic force between IgG and Co-MOF-OH. The enrichment factor for IgG is high, up to 97.7 for enriching IgG from the IgG/human serum albumin mixture with a mass ratio of 1:50, and circular dichroism indicates that the enrichment process poses no influence on the protein structure. Moreover, Co-MOF-OH proves its practicability in complex biological samples by the selective extraction of IgG from complex human serum samples.

Melamine foam assisted in-tip packed amine-functionalized titanium metal-organic framework for the selective enrichment of endogenous glycopeptides

Endogenous glycopeptides are significantly important in diverse pathological and physiological systems, but their direct analysis is severely hampered by their low abundance and presence of interfering species in biological fluids. In this study, we synthesized the amine-functionalized titanium metal-organic framework (NH₂-MIL-125(Ti)) by a simple hydrothermal method, characterized and used for glycopeptides enrichment. The designed separation media is highly hydrophilic and stable which is suitable for hydrophilic interaction chromatography (HILIC). To make the process smooth, simple, reliable, and robust, NH₂-MIL-125(Ti) crystals were packed in pipette-tip using hydrophilic melamine foam, as supporting frit. Free amine groups, present in the structure imparted hydrophilicity and a unique pattern of porosity, contributing to the size exclusion effect that excluded the large-sized proteins up to 1:700 peptide to protein ratio. The prepared MOF particles possessed regular porosity, high surface area, good hydrophilicity, and offered an in-tip flow-based set-up enhanced the enrichment performance for N-linked glycopeptides. The affinity material showed a detection limit of 1 fmol.µL^-1 and selectivity up to 1:1000 (HRP digest to BSA digest). Moreover, repeatability and reusability were evaluated up to five rounds of enrichment using the same affinity tip, and scanning electron microscopic images revealed no structural changes in the MOF crystals. Finally, the MOF packed in pipette tip was applied to selectively capture the N-linked endogenous glycopeptides from a healthy saliva sample and 64 unique endogenous glycopeptides were identified. These results demonstrated the excellent potential of NH₂-MIL-125(Ti) based affinity tip for glycopeptides which can be used to enrich trace glycopeptide biomarkers from the biological fluids.

Recent Advances in Affinity MOF-Based Sorbents with Sample Preparation Purposes

This review summarizes the recent advances concerning metal-organic frameworks (MOFs) modified with several biomolecules (e.g., amino acids, nucleobases, proteins, antibodies, aptamers, etc.) as ligands to prepare affinity-based sorbents for application in the sample preparation field. The preparation and incorporation strategies of these MOF-based affinity materials were described. Additionally, the different types of ligands that can be employed for the synthesis of these biocomposites and their application as sorbents for the selective extraction of molecules and clean-up of complex real samples is reported. The most important features of the developed biocomposites will be discussed throughout the text in different sections, and several examples will be also commented on in detail.

Gold nanoparticle-glutathione-functionalized porous graphene oxide-based hydrophilic beads for the selective enrichment of N-linked glycopeptides

A three-dimensional structured porous graphene oxide-polyethylenimine bead (pGP) is synthesized for immobilizing gold nanoparticles and modifying glutathione molecules (denoted as pGP/AuG). The pGP/AuG has open pore structure, honeycomb-like channels, and excellent hydrophilicity. By taking advantages of the porous structure, abundant binding sites, and multivalent interactions between glycopeptides and both glutathione molecules and free amino groups, the pGP/AuG is adopted to the selective enrichment of N-linked glycopeptides with low limit of detection (2 fmol), high enrichment selectivity (1:500), binding capacity (333.3 mg/g), recovery yield (91.3 ± 2.1%), and repeatability (< 6.0% RSD) using matrix-assisted laser desorption/ionization time of flight mass spectrometry detection method. Furthermore, the practical applicability of pGP/AuG is evaluated, in which 209 N-glycosylated peptides corresponding to 128 N-glycosylated proteins are identified from 1 μL human serum in three independent analysis procedures, suggesting the great potential for application in glycoproteome fields.Graphical abstract Schematic presentation of preparation for porous graphene oxide-based hydrophilic beads (pGP/AuG) with honeycomb-like microstructure. The pGP/AuG was successfully used for enriching and identifying glycopeptides from actual biological sample.

A novel Wulff-type boronate acid-functionalized magnetic metal-organic framework imprinted polymer for specific recognition of glycoproteins under physiological pH

Boronate affinity molecularly imprinted materials have been widely used for the separation of glycoproteins under alkaline conditions that is not conducive to the structural stability of the protein. In this work, a kind of novel molecularly imprinted polymer (MIP/TBA/MOF@Fe₃ O₄ ) was prepared via grafting self-assembled molecular team of boronic acids on the surface of the magnetic metal-organic framework core. The teamed boronate affinity was formed by 2-mercaptoethylamine and 4-mercaptophenylboronic acid for specific separation of glycoproteins under physiological pH (pH 7.4). The obtained nanoparticles show high binding capacities (337.8 mg/g), fast adsorption equilibrium time (20 min), and good specificity (imprinting factor, 4.52) for glycoproteins under physiological pH. Furthermore, the prepared imprinted polymer still shows good adsorption capacity for glycoprotein after five times of repeated use, and its adsorption capacity only dropped by 4.7%. More importantly, the prepared nanoparticles have good potential to adsorb glycoproteins from real biological samples.

Ultrathin Hexagonal PbO Nanosheets Induced by Laser Ablation in Water for Chemically Trapping Surface-Enhanced Raman Spectroscopy Chips and Detection of Trace Gaseous H2S

Lead oxide (PbO) nanosheets are of significance in the design of functional devices. However, facile, green, and fast fabrication of ultrathin and homogenous PbO nanosheets with a chemically clean surface is still desirable. Herein, a simple and chemically clean route is developed for fabricating such nanosheets via laser ablation of a lead target in water for a short time and then ambient aging. The obtained PbO nanosheets are (002)-oriented with microsize in planar dimension and ∼15 nm in thickness. They are mostly hexagonal in shape. Experimental observations of the morphological evolution have revealed that the formation of such PbO nanosheets can be attributed to two processes: (i) laser ablation-induced formation of ultrafine Pb and PbO nanoparticles (NPs) and (ii) PbO NP aggregation and their oriented connection growth. Importantly, a composite surface-enhanced Raman spectroscopy (SERS) chip is designed and fabricated by covering a PbO nanosheet monolayer on a Au NP film. Such a composite SERS chip can be used for the fast and trace detection of gaseous H₂S in which the PbO nanosheets can effectively chemically trap H₂S molecules, demonstrating a new application of these PbO nanosheets. The response of this chip to H₂S can be detected within 10 s, and the detection limit is below 1 ppb. Also, this PbO nanosheet-based chip is reusable by heating after use. This study not only deepens the understanding of the NP-based formation mechanism of nanosheets but also provides the renewable SERS chips for the highly efficient detection of trace gaseous H₂S.

MOF-Based Photonic Crystal Film toward Separation of Organic Dyes

Metal-organic framework (MOF)-directed photonic structure materials have inspired great attention for extended and enhanced functions. However, the direct construction of photonic crystals (PCs) with MOF particles as building blocks still remains a challenge. Herein, we designed and synthesized monodisperse polyamidoamine (PAMAM) dendrimer-modified zeolitic imidazolate framework (ZIF-8) particles (PAMAM@ZIF-8) via a postsynthetic method, rendering ZIF-8 with hydrophilicity. It was found that the PAMAM@ZIF-8 particles could directly assemble into a uniform photonic structure and effectively suppressed the coffee-ring effect, forming homogeneous PC films with different structural colors. A PC pattern with angle-dependent colors was also achieved, which might have potential applications in the field of anticounterfeiting printing. More importantly, by taking advantages of a membrane separation-assisted assembly process, a colorful and robust PC film was accomplished on the surface of reduced graphene oxide (rGO). The hierarchal PAMAM@ZIF-8/rGO film demonstrates a superior separation ability toward organic dye solutions, which enriches the function of PC materials. This work gives a new insight into the fabrication of MOF-based functional PC materials, which will extend the application of PCs in the high selective and effective separation field.

Engineering of Nanoscale Coordination Polymers with Biomolecules for Advanced Applications

Nanoscale coordination polymers (NCPs) have shown extraordinary advantages in various research areas due to their structural diversity and multifunctionality. Recently, integration of biomolecules with NCPs received extensive attention and the formed hybrid materials exhibit superior properties over the individual NCPs or biomolecules. In this review, the state-of-the-art of approaches to engineer NCPs with different types of guest biomolecules, such as amino acids, nucleic acids, enzymes and lipids are systematically introduced. Additionally, advanced applications of these biomolecule-NCP composites in the areas of sensing, catalysis, molecular imaging and therapy are thoroughly summarized. Finally, current challenges and prospects are also discussed.

L-cysteine functionalized straticulate C3N4 for the selective enrichment of glycopeptides

The facile enrichment of glycopeptides or glycoproteins poses great challenges for glycoproteomic research. In this study, a novel hydrophilic material, named zwitterionic hydrophilic L-cysteine derivatized straticulate-C₃N₄ composites (LCAC), were synthesized and evaluated for the enrichment of N-glycopeptides. LCAC exhibited good biocompatibility, excellent hydrophilicity and selectivity, by virtue of the large surface of C₃N₄ and the zwitterionic property offered by cysteine. LCAC demonstrated excellent performance for N-glycopeptide enrichment with the sensitivity of 0.033 fmol/µL, selectivity of 1:100, and high recovery rate (∼85%). The performance of LCAC was demonstrated by the identification of 35 N-glycopeptides from IgG, as well as capturing 1809 human urine N-glycopeptides corresponding to 876 N-glycoproteins. Comparing the LCAC with our developed phenylboronic acid functionalized material showed a certain complementary due to the different binding mechanism. The simple production and enhanced hydrophilic properties make the material a promising choice for glycoproteomics researches.

A magnetic nanofiber-based zwitterionic hydrophilic material for the selective capture and identification of glycopeptides

High-performance affinity materials are highly required in the sample preparation process in mass spectrometry-based glycoproteomics studies. In this research, a novel magnetic nanofiber-based zwitterionic hydrophilic material is prepared for glycopeptide enrichment and identification. The one-dimensional hydroxyapatite nanofiber (HN) acted as the supporting substance for immobilizing both Fe3O4 nanoparticles and Au nanoparticles, following the surface modification with a zwitterionic tripeptide l-glutathione (GSH) via the affinity interactions between the thiol group in GSH and both Au and Fe3O4 to form the magHN/Au-GSH nanofiber. Owing to the unique structural features, excellent hydrophilicity, abundant zwitterionic molecules, and strong magnetic responsiveness, the as-prepared magHN/Au-GSH nanofiber possesses satisfactory specificity for glycopeptide enrichment. As a result, the magHN/Au-GSH nanofiber demonstrated great detection sensitivity (2 fmol), satisfying enrichment recovery (89.65%), large binding capacity (100 mg g-1), and high enrichment selectivity (1 : 100) toward glycopeptides. Furthermore, 246 N-glycosylated peptides corresponding to 104 N-glycosylated proteins were identified from only 1 μL human serum, revealing the great potential of this affinity nanofiber for glycopeptide enrichment and glycoproteomics research.

Preparation of a thickness-controlled Mg-MOFs-based magnetic graphene composite as a novel hydrophilic matrix for the effective identification of the glycopeptide in the human urine

The highly effective analysis of glycopeptides from complex biological samples is an attractive and critical topic all the time. In this study, a novel thickness-controlled hydrophilic Mg-metal organic frameworks (Mg-MOFs) coating-functionalized magnetic graphene composite (MagG@Mg-MOFs-1C) was prepared for the capture of the glycopeptides. The as-synthesized composite exhibits an ultralow limit of detection (0.1 fmol μL-1), a perfect size-exclusion effect (HRP digests/BSA protein/HRP protein, 1 : 500 : 500, w/w/w), and a high binding capacity (150 mg g-1), satisfying reusability and high recovery in the recognition of glycopeptides due to its outstanding characteristics including strong magnetic property, large surface area (617 m2 g-1), plenty of affinity sites, and excellent hydrophilicity. Furthermore, the MagG@Mg-MOFs-1C composite was successfully applied to selectively enriched glycopeptides in human urine. More excitingly, 406 N-glycosylation peptides corresponding to 185 glycoproteins were identified in the urine of the bladder cancer patients, in which these identified glycoproteins include the potential biomarkers (α-2-macroglobulin, complement C4-B, and α-1-antitrypsin) for the bladder cancer. This study suggests that the hydrophilic porous MOFs-functionalized composite has a great potential in the large-scale characterization of the low-abundance biomolecules in urine, opening a new avenue for the rapid and convenient diagnosis of the disease.

Advances in hydrophilic nanomaterials for glycoproteomics

Owing to the formidable challenge posed by microheterogeneities in glycosylation sites, macroheterogeneity of the modification number of glycans, and low abundance and ionization efficiency of glycosylation, the crucial premise for conducting in-depth profiling of the glycoproteome is to develop highly efficient technology for separation and enrichment. The appearance of hydrophilic interaction chromatography (HILIC) has considerably accelerated the progress in glycoproteomics. In particular, additional hydrophilic nanomaterials have been developed for glycoproteomics research in the recent years. In this review, we mainly summarize the recent progresses made in the design and synthesis of different hydrophilic nanomaterials, as well as their applications in glycoproteomics, according to the classification of the main hydrophilic functional molecules on the surface. Further, we briefly illustrate the potential retention mechanism of the HILIC mode and discuss the limits and barriers of hydrophilic nanomaterials in glycoproteomics, as well as propose their possible development trends in the future.