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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 Fe 3 O 4 @RF@Zr-BCP nanochains feature excellent magnetic response (42.26 emu/g), high hydrophilicity (16.0°), and large specific surface area (140.84 m 2 /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 Fe 3 O 4 @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 Fe 3 O 4 @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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Protein glycosylation plays a vital role in many physiological activities in organisms. Due to the low abundance of glycopeptides and the interference of numerous non-glycopeptides in biological samples, selective enrichment of glycopeptides is of great significance for their successful identification. Metal organic frameworks (MOFs) materials are appropriate for glycopeptides enrichment by virtue of their large specific surface area and outstanding hydrophilic properties. However, the instability of hydrophilic MOFs in acidic solutions have severely limited their applications. In this work, a rational facile strategy was established to synthesize a stable hydrophilic hierarchical porous MOF (denoted as HP-MOF-Arg@mSiO 2 ). This new material improved the selectivity and sensitivity of enrichment for glycopeptides via modification of arginine groups. More importantly, the mesoporous silica layer was introduced to enhance the stability of MOFs in aqueous solution and achieve the size exclusion effect of large-size proteins in complex samples. Overall, owing to the unique hierarchical porous and the hydrophilic modification, the synthesized HP-MOF-Arg@mSiO 2 materials showed excellent hydrophilicity and hydrolytic stability, resulting in outstanding specific separation capacity in glycopeptides enrichment. A total of 521 and 342 glycopeptides were respectively captured from 2 μL human serum digests and mouse testis tissue digests, revealing the potential of the materials in the study of glycoproteomics in complex biological samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Protein glycosylation is among the most important post-translational modifications in living organisms and the research in the field of protein glycosylation continues to garner attention. Currently, the efficient separation and enrichment of glycoproteins and glycopeptides is the primary challenge of glycoproteomics research. The number of glycoproteins is small in complex biological samples. Moreover, the presence of highly-abundant, non-glycosylated, and modified peptides makes the detection of low-abundance glycopeptides more difficult. Therefore, efficient glycopeptide enrichment methods are required to improve the detection of these compounds. The development of highly selective glycopeptide enrichment tools is important to efficiently capture glycoproteins or glycopeptides at the molecular level. Compared with traditional glycopeptide-enriched materials, covalent organic framework materials have the advantages of large specific surface area and rich modification sites, thereby exhibiting great application potential in the field of glycopeptide enrichment. In this study, a novel covalent organic framework material (O-T-D-COFs) was prepared and applied for selective glycopeptide enrichment. We applied the solvothermal method, using 2,5-dimethoxy benzene-1,4-2 formaldehyde and 1,3,5-Tris(4-aminophenyl) benzene, to synthesize imino-based COFs. The Schiff base generated via copolymerization condensation reaction constitutes the framework of the material. Next, the synthesized intermediate material was oxidized to improve the enrichment performance of the material. The functional, specific glycopeptide-binding groups were modified on the COF channels and the structure of the material was characterized using scanning and transmission electron microscope, as well as infrared spectrum and solid-state nuclear magnetic resonance. The enrichment conditions comprised the loading and elution steps, including the optimization of the elution conditions. We could observe the clear profile of 32 glycopeptides derived from human serum immunoglobulin G (IgG) tryptic digests with a significantly improved signal-to-noise ( S/N ) ratio. We applied a complex sample system to verify the enrichment selectivity of the material when the molar ratios of the IgG and bovine serum albumin (BSA) tryptic digest mixtures reached 1∶50. In addition, we investigated the enrichment performance of the detection limit, enrichment capacity, recovery rate of the material, and the application potential in glycopeptides enrichment using real samples. The material showed a good detection limit (2.5 fmol/μL), an ideal enrichment capacity (120 mg/g), and enrichment recovery (103.5%±6.6% and 101.5%±10.4%). We identified a total of 86 glycopeptides derived from 53 glycoproteins with 94 N -glycosylation sites from only 1 μL human serum. The O-T-D-COFs exhibited a good glycopeptide separation and enrichment potential, indicating that the COF material has promising application potential in glycoproteomics.

A selectively modified porous metal/carbon nanocomposite was fabricated to enhance the enrichment of low-abundance phosphopeptides from biological samples. The carbon matrix derived from the metal-organic framework provides a suitable pore size to allow the diffusion of peptides, while the deliberately modified metal nanoparticles within the pores enhance their interaction with the phosphopeptides. This nanocomposite shows extremely high enrichment selectivity for phosphopeptides in the MALDI-TOF MS detection, even when the molar ratio of α-casein digests versus bovine serum albumin digests was up to about 1:20,000. By combining such nanocomposite with nano-LC-MS/MS, 4556 unique phosphopeptides were identified with high selectivity (95.2%) from HeLa cell extracts. Furthermore, phosphopeptides from prostate tissue digests were also determined. A total of 277 and 1242 phosphopeptides were identified from normal and tumor tissues of a patient with prostate cancer, respectively. This indicates that phosphorylation and prostate cancer can be related to each other.

In view of the size and hydrophilicity of glycopeptides, materials having suitable channels (size-exclusion) and strong hydrophilic surface (hydrophilic interaction) are preferred to enrich the glycopeptides in biological samples. Metal-organic frameworks (MOFs) are good candidates. However, their smaller microporous channels and low chemical stability have limited the application. Herein, a facile strategy was established to construct hydrophilic mesoporous MOF via synergistic etching and surface functionalization by using phytic acid (PA). Besides, polyvinylpyrrolidone (PVP) was added during MOF synthesis to enhance the water stability of the MOF. Owing to the expanded hydrophilic mesoporous channels, the PA-modified Ce-MOF effectively and selectively captured 422 glycopeptides from 155 glycoproteins in tryptic digests of human serum (2 μL). The present work sheds light on the easy fabrication of hydrophilic mesoporous materials, and this established material holds unique advantages for glycopeptides analysis in biological samples.

In this work, we presented a facile elution-free method for ultrasensitive enrichment of glycopeptides using two kinds of novel Ce-metal-organic frameworks (Ce-MOF) post-modified with hyaluronic acid (Ce-MOF@HA) and glutamic acid (Ce-MOF@Glu). Both of the synthesized materials remained stable in the loading buffer to enrich glycopeptides selectively and degrade in the eluent to release captured glycopeptides. Due to the dissolution of materials, the elution step of the enrichment process is omitted, resulting in an extremely high sensitivity (detection limit, 0.5 fmol/μL). Meanwhile, Ce-MOF@HA and Ce-MOF@Glu also possessed excellent selectivity with molar ratios of IgG and BSA digests being 1:1000 and 1:500, respectively. Noticeably, the practical applicability of the obtained materials was inspected by analyzing the glycopeptides enriched from human serum (2 μL) by nano-LC-MS, in which 434 N-glycopeptides from 182 N-glycoproteins (by Ce-MOF@HA) and 328 N-glycopeptides from 135 N-glycoproteins (by Ce-MOF@Glu) were detected, respectively. This work provides a new method to simplify the process of glycopeptides enrichment and also paves a novel way for the enrichment of trace targets from complex matrices., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Abstract: In this work, a metal‐organic frameworks‐based porous carbon was explored for glucose oxidase immobilization and glucose sensing. ZIF‐67 was chosen as the precursors for the calcination treatment. The formed Co nanoparticles induced the graphitization of the carbon during the carbonization, resulting in a good conductivity. The followed HCl treatment partly removed the formed Co nanoparticles to give a larger specific surface area of the porous carbon due to the generated space voids from the dissolved Co nanoparticles. The resulting MOFs‐derived porous carbon show an improved loading performance toward glucose oxidase, and fast electron transfer was also demonstrated. This work proves the MOFs‐derived porous carbon as a novel and outstanding platform for the enzymatic electrocatalysis for the sensors and energy conversion devices. [ABSTRACT FROM AUTHOR]

Whereas metal-organic frameworks (MOFs) are being widely explored in the application of electrocatalysis, the electro-inert organic ligands in MOFs have negative effects on electron transfer. Here, we suggest a facile electrochemical cathodization treatment for the controllable evolution of a Cu-MOF to improve its electrocatalytic performance. When a cathodic potential was applied, Cu-based structures evolving from Cu-MOF with different crystal phases, surface compositions, and morphologies were harvested by controlling the cathodization time. The obtained copper-based structures were found to have much higher activities than the as-synthesized Cu-MOF for glucose electrocatalysis in alkaline media. A 60 second cathodization treatment resulted in the largest sensitivity for glucose electrocatalytic sensing. [ABSTRACT FROM AUTHOR]

The Inside Back Cover picture shows that the cathodization treatment on Cu–MOF results in the evolution of a structure with improved electrocatalytic activity for glucose oxidation. More information can be found in the Communication by H. Zhao, M. Lan and co‐workers on page 246 in Issue 2, 2017 (DOI: 10.1002/celc.201600625). [ABSTRACT FROM AUTHOR]

Abstract Quantification of superoxide anions (O 2 −) is of great significance for the pathological research of many diseases. In this work, a non-enzymatic electrochemical sensor for superoxide sensing was fabricated on the basis of metal-organic frameworks (MOFs)-derived porous carbon matrix loaded with Pt and Co nanoparticles (denoted as Pt-Co-PC). Zeolitic imidazolate framework-67 (ZIF-67) was utilized as the precursor through a one-step calcination under N 2 atmosphere to prepare cobalt nanoparticles-porous carbon composites (denoted as Co-PC). Pt-Co-PC was then obtained by using a facile galvanic replacement procedure with Co-PC and chloroplatinic acid solution. Furthermore, the home-made screen printed gold electrodes (SPGEs) were used to immobilize the as-synthesized materials, constructing Pt-Co-PC modified electrochemical sensors. The recommended Pt-Co-PC/SPGE sensors exhibit excellent electrochemical performance for the detection of O 2 − with an extremely low detection limit of 0.118 μM (S/N = 3) and a high sensitivity of 6.218 × 10−4 mA μM−1 cm−2. Meanwhile, the proposed sensors possess superior reproducibility and stability. More importantly, our sensors have successfully captured the electrochemical signals of O 2 − released from Hela cells, which means the fabricated sensors have potential application of monitoring O 2 − in pathological and biological fields. Highlights • A facile method to fabricate porous carbon matrix loaded with Pt and Co nanoparticles. • A novel non-enzymatic O 2 − sensor was established. • The recommended sensors can successfully capture the electrochemical signals of O 2 − released from Hela cells. [ABSTRACT FROM AUTHOR]

Calcination of metal-organic frameworks (MOFs) with designed condition is an efficient and flexible method to synthesize electrocatalysts with high activity toward various applications. In this work, we propose a facile calcination procedure under N 2 atmosphere utilizing zeolitic imidazolate framework-67 (ZIF-67) as the precursor to obtain cobalt nanoparticles-porous carbon composites (denoted as ZIF-N 2 ) for nonenzymatic glucose detection in alkaline media. At the same time, calcination of ZIF-67 under air atmosphere with the same temperature was also carried out. The resulting product (denoted as ZIF-Air) was used as a comparison when evaluating the electrochemical performance of ZIF-N 2 . By means of a series of physicochemical and electrochemical characterizations, different calcination atmosphere show great effect on the properties of the resulting materials. ZIF-N 2 shows the specific morphology with Co nanoparticles loaded on the porous carbon matrix, with superior conductivity, mass activity, and electrochemical effective surface area to ZIF-Air. Based on these distinct parameters, nearly 10 times higher response of ZIF-N 2 is obtained toward glucose than that of ZIF-Air. The sensitivity of ZIF-N2 is calculated to be 0.227 mA mM − 1 cm − 2 in the linear range of 0.1–1.1 mM, with LOD of 5.69 μM. Finally, the nonenzymatic glucose sensing performance of ZIF-N 2 modified screen-printed carbon electrode including selectivity, long-term stability and reproducibility were also proved to be outstanding. This work demonstrates the calcination of MOFs under designed condition can be a promising method to obtain electrocatalysts for electrochemical sensing application. [ABSTRACT FROM AUTHOR]

In this work, we applied metal-organic frameworks (MOFs) as a porous matrix to encapsulate Cu nanoparticles (NPs) for nonenzymatic glucose sensing in alkaline media. SEM and TEM confirmed that the size of the encapsulated Cu NPs ranges from 2.5 to 5 nm. The hybrid of Cu NPs encapsulated in ZIF-8 (Cu-in-ZIF-8) was further modified onto screen-printed electrodes for nonenzymatic sensing of glucose in alkaline medium. The porous structure of ZIF-8 are beneficial for the unimpeded diffusion of glucose and reaction product. And as a matrix for encapsulating Cu NPs, ZIF-8 also protect the Cu NPs from dissolution and agglomeration during the electrocatalytic process. For comparison, the electrochemical performance of Cu NPs loaded on ZIF-8 (Cu-on-ZIF-8) was also investigated and it is found that Cu-in-ZIF-8 exhibited higher activity and better stability for cyclic test toward the oxidation of glucose in alkaline media. Additionally, Cu-in-ZIF-8 based glucose sensor also shows a favorable sensitivity and selectivity. [ABSTRACT FROM AUTHOR]