Facile synthesis of guanidyl-based magnetic ionic covalent organic framework composites for selective enrichment of phosphopeptides

Recent advances and applications of ionic covalent organic frameworks in food analysis

Ionic covalent organic frameworks with both crystallinity and charged sites have attracted significant attention from the scientific community. The versatile textural structures, precisely defined channels, and abundant charged sites of ionic COFs offer immense potential in various areas such as separation, sample pretreatment, ion conduction mechanisms, sensing applications, catalytic reactions, and energy storage systems. This review presents a comprehensive overview of facile preparation methods for ionic covalent organic frameworks (iCOFs), along with their applications in food sample pretreatment techniques such as solid-phase extraction (SPE), magnetic solid-phase extraction (MSPE), and dispersive solid-phase extraction (DSPE). Furthermore, it highlights the extensive utilization of iCOFs in detecting various food contaminants including pesticides, contaminants from food packaging, veterinary drugs, perfluoroalkyl substances, and poly-fluoroalkyl substances. Specifically, this review critically discusses the limitations, challenges, and future prospects associated with employing iCOF materials to ensure food safety.

Ionic liquid-functionalized covalent organic frameworks on the surface of silica for online solid-phase extraction

A covalent organic framework (COF) was gown on porous silica with 1,3,5-tri(4-aminophenyl)benzene and 2,5-divinyl-1,4-phenyldiformaldehyde as monomers, and two ionic liquids were grafted to COF by a click reaction. The materials before and after the modification of ionic liquids were separately packed into solid-phase extraction columns (10 × 4.6 mm, i.d.), which were coupled with liquid chromatography to construct online analysis systems. The extraction mechanisms of polycyclic aromatic hydrocarbons, bisphenols, diphenylalkanes and benzoic acids were investigated on these materials. There were π-π, hydrogen-bond and electrostatic interactions on ionic liquid-functionalized sorbents. After the comparison among these materials, the best sorbent was used, and the analytical method was established and successfully applied to the detection of some estrogens from actual samples. For the analytical method, the detection limit was as low as 0.005 μg L-1, linear range was as wide as 0.017-10.0 μg L-1, and enrichment ratio was as high as 3635. The recoveries in actual samples were 70 %-129 %.

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.

Facile synthesis of Fe3+ immobilized magnetic polydopamine-polyethyleneimine composites for phosphopeptide enrichment

As one of the most common post-translational modification of proteins, protein phosphorylation plays a vital role in many physiological processes. The enrichment of phosphopeptides is highly important before the mass spectrometry detection since phosphopeptides are susceptible to interferences from high-abundance non-phosphopeptides. In this study, we designed a novel magnetic composite (Fe3O4@PDA-PEI-Fe3+) for phosphopeptide enrichment with a facile protocol. The developed Fe3O4@PDA-PEI-Fe3+ is a marvelous material with multiple functional groups, and can effectively enrich phosphopeptides through the synergistic effect of three mechanisms, i.e., immobilized metal ion affinity chromatography raised form Fe3+, electrostatic interaction between amine and phosphate groups, and hydrogen bond between the hydrogen atoms of amine groups and oxygen atoms of phosphate groups. Combined with mass spectrometry, the material shows excellent enrichment performance, high sensitivity (0.4 fmol), good selectivity (β-casein:BSA= 1:500, w:w), and stable reusability (at least 5 cycles). In addition, the material was successfully applied to enrich phosphopeptides from skim milk and human saliva samples, implying that it is an ideal adsorbent for the phosphopeptide enrichment in complex biological samples and provides valuable insights into the field of phosphopeptide analysis.

Enrichment of phosphopeptides by arginine-functionalized magnetic chitosan nanoparticles

One of the most crucial and prevalent post-translational modifications is the phosphorylation of proteins. The study and examination of protein phosphorylation hold immense importance in comprehending disease mechanisms and discovering novel biomarkers. However, the inherent low abundance, low ionization efficiency, and coexistence with non phosphopeptides seriously affect the direct analysis of phosphopeptides by mass spectrometry. In order to tackle these problems, it is necessary to carry out selective enrichment of phosphopeptides prior to conducting mass spectrometry analysis. Herein, magnetic chitosan nanoparticles were developed by incorporating arginine, and were then utilized for phosphopeptide enrichment. A tryptic digest of β-casein was chosen as the standard substance. After enrichment, combined with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), the detection limit of the method was 0.4 fmol. The synthesized magnetic material demonstrated great potential in the detection of phosphopeptides in complex samples, as proven by its successful application in detecting phosphopeptides in skim milk and human saliva samples.

Drug delivery using biocompatible covalent organic frameworks (COFs) towards a therapeutic approach

Covalent organic frameworks (COFs) are constructed exclusively with lightweight organic scaffolds, which can have a 2D or 3D architecture. The ease of synthesis, robust skeleton and tunable properties of COFs make them superior candidates among their counterparts for a wide range of uses including biomedical applications. In the biomedical field, drug delivery or photodynamic-photothermal (PDT-PTT) therapy can be individually considered a potential parameter to be investigated. Therefore, this comprehensive review is focused on drug delivery using COFs, highlighting the encapsulation and decapsulation of drugs by COF scaffolds and their delivery in biological media including live cells. Versatile COF scaffolds together with the delivery of several drug molecules are considered. We attempted to incorporate the status of drug encapsulation and decapsulation considering a wide range of recent publications.

Post-synthesis of a titanium-rich magnetic COF nanocomposite with flexible branched polymers for efficient enrichment of phosphopeptides from human saliva and serum

A Ti4+-functionalized magnetic covalent organic framework material with flexible branched polymers (mCOF@ε-PL@THBA-Ti4+) built via an immobilized metal ion affinity chromatography (IMAC) enrichment strategy was proposed through post-synthesis modification. Hydrophilic ε-poly-L-lysine (ε-PL) rich in amino active groups was first introduced in the fabrication of the phosphopeptide enrichment material to increase the hydrophilicity while providing more functional modification pathways of the material. 2,3,4-Trihydroxy-benzaldehyde (THBA) provides abundant binding sites for the immobilization of numerous Ti4+, which is advantageous for the subsequent efficient phosphopeptide enrichment. The magnetic nanocomposite exhibited outstanding performance of phosphopeptide enrichment with good selectivity (1 : 5000), a low detection limit (2 fmol), and relatively high loading capacity (66.7 mg g-1). What's more, after treatment with mCOF@ε-PL@THBA-Ti4+, 16 endogenous phosphopeptides from fresh saliva of healthy people were recognized by MALDI-TOF MS, and 50 phosphopeptides belonging to 35 phosphoproteins from the serum of uremia patients were detected by nano-LC-MS/MS. Proteomics data analysis for the differential protein selection between uremia and normal controls was conducted using R software, and four down-regulated and three up-regulated proteins were obtained. The results suggested that the prepared material has potential applications in biomarker discovery.

Rational Fabrication of Ionic Covalent Organic Frameworks for Chemical Analysis Applications

The rapid development of advanced material science boosts novel chemical analytical technologies for effective pretreatment and sensitive sensing applications in the fields of environmental monitoring, food security, biomedicines, and human health. Ionic covalent organic frameworks (iCOFs) emerge as a class of covalent organic frameworks (COFs) with electrically charged frames or pores as well as predesigned molecular and topological structures, large specific surface area, high crystallinity, and good stability. Benefiting from the pore size interception effect, electrostatic interaction, ion exchange, and recognizing group load, iCOFs exhibit the promising ability to extract specific analytes and enrich trace substances from samples for accurate analysis. On the other hand, the stimuli response of iCOFs and their composites to electrochemical, electric, or photo-irradiating sources endows them as potential transducers for biosensing, environmental analysis, surroundings monitoring, etc. In this review, we summarized the typical construction of iCOFs and focused on their rational structure design for analytical extraction/enrichment and sensing applications in recent years. The important role of iCOFs in the chemical analysis was fully highlighted. Finally, the opportunities and challenges of iCOF-based analytical technologies were also discussed, which may be beneficial to provide a solid foundation for further design and application of iCOFs.

An easy and straightforward synthesized nano calcium phosphate for highly capture of multiply phosphorylated peptides

Multisite phosphorylation of proteins regulates various cellular life activities, however, the capture of low abundance multi-phosphopeptides from biosamples and identification of phosphorylation sites are largely limited due to the limited enrichment materials and their unclear interactions with multi-phosphopeptides. Here we propose using two cheap raw materials (CaCl₂·2H₂O and Na₂HPO₄·12H₂O) in 10 min at room temperature to synthesize the structurally simple Nanometric Calcium Phosphate (CaP) to resolve this challenge. The current results showed that the "simple" CaP has good selection specificity, high sensitivity and stability for multi-phosphopeptides enrichment and the identification of phosphorylation sites, which facilitate the popularization and application of phosphoproteomics research. Further, the interaction of CaP and multi-phosphopeptides were qualitatively characterized at the molecular/atomic level and the high affinity between them was quantified by the isothermal titration microcalorimeter based on the laws of thermodynamics. The results indicated that the interaction was a spontaneous (ΔG < 0) exothermic reaction with enthalpy reduction (ΔH < 0) and driven mainly by hydrogen bond and electrostatic interaction process.

Preparation and modification of PS-PMMA microspheres and their application in high performance liquid chromatography

Polymer microspheres have been widely used as a stationary phase for liquid chromatography. In this work, we prepared and synthesized polystyrene-methyl methacrylate (PS-PMMA) microspheres, modified them, characterized the microspheres to have good chromatographic properties, and then used them as a high-performance liquid chromatography (HPLC) stationary phase to explore their applications. First, the PS-PMMA microspheres were hydrolyzed, and the separation of benzene homologues/alkaloids was explored. Then, on the basis of hydrolysis, diazo resin (DR) was used as a coupling agent to further modify the surface of the microspheres with amphoteric glycopeptide vancomycin. The modified microspheres were used as a HPLC stationary phase to explore the application of the stationary phase in the separation of chiral drugs. This work is important to broaden the application of functional chiral columns for antibiotics and to expand the application of PS-PMMA microspheres in HPLC.

Covalent Organic Frameworks with Ionic Liquid-Moieties (ILCOFs): Structures, Synthesis, and CO2 Conversion

CO₂, an acidic gas, is usually emitted from the combustion of fossil fuels and leads to the formation of acid rain and greenhouse effects. CO₂ can be used to produce kinds of value-added chemicals from a viewpoint based on carbon capture, utilization, and storage (CCUS). With the combination of unique structures and properties of ionic liquids (ILs) and covalent organic frameworks (COFs), covalent organic frameworks with ionic liquid-moieties (ILCOFs) have been developed as a kind of novel and efficient sorbent, catalyst, and electrolyte since 2016. In this critical review, we first focus on the structures and synthesis of different kinds of ILCOFs materials, including ILCOFs with IL moieties located on the main linkers, on the nodes, and on the side chains. We then discuss the ILCOFs for CO₂ capture and conversion, including the reduction and cycloaddition of CO₂. Finally, future directions and prospects for ILCOFs are outlined. This review is beneficial for academic researchers in obtaining an overall understanding of ILCOFs and their application of CO₂ conversion. This work will open a door to develop novel ILCOFs materials for the capture, separation, and utilization of other typical acid, basic, or neutral gases such as SO₂, H₂S, NOx, NH₃, and so on.

Epitaxial Growth of Guanidyl-Functionalized Magnetic Metal-Organic Frameworks with Multiaffinity Sites for Selective Capture of Global Phosphopeptides

The flexible and controlled synthesis of metal-organic framework (MOF)-derived hybrid nanostructures is of great significance in fine tuning of their enrichment performance in large-scale and in-depth phosphoproteome analysis. Herein, a magnetic guanidyl-functionalized MOF hybrid coating with multiaffinity sites, denoted as Fe₃O₄@G-ZIF-8, was fast fabricated via a one-pot epitaxial growth strategy for the first time and applied for selective and highly efficient enrichment of global phosphopeptides. The intrinsic unsaturated metal sites of ZIF-8 endow the surface-mounted MOF coatings with immobilized metal ion affinity chromatography interaction with multiphosphorylated peptides. The oriented anchoring of bifunctional guanidineacetic acid on the magnetic MOF nanospheres provides additional affinity sites (guanidyl groups) for specific recognition of phosphopeptides by "salt bridge" interaction, as well as active site carboxyl groups for the coordination with the metal ions. The as-prepared Fe₃O₄@G-ZIF-8 exhibits large surface area (382.5 m² g^-1), good superparamagnetic property (41.6 emu g^-1) and stability, and size-exclusion effect (1.73 nm), which can serve as a specific adsorbent for global phosphopeptide analysis with satisfactory selectivity, great detection sensitivity (1 fmol), and rapid magnetic separation. Moreover, the successful application of Fe₃O₄@G-ZIF-8 for selective capture of both multi- and mono-phosphopeptides from human saliva and serum demonstrated the great potential of magnetic surface-mounted MOF coatings in effective identification of low-abundance phosphopeptides by matrix-assisted laser desorption ionization time-of-flight mass spectrometry from complicated biological matrices.

Magnetic Covalent Organic Frameworks-Fundamentals and Applications in Analytical Chemistry

Magnetic covalent organic frameworks are new emerging materials which, besides many other applications, have found unique applications in analytical chemistry as separating media and adsorbents. They have outstanding features such as special morphology, chemical and thermal stability, high adsorption capacity, good magnetic response, high specific surface area, uniform pore size distribution, strong π-π interactions with analytes and high reusability that makes reported studies on their properties and applications increased in the recent years. After discussing the methods of synthesis of MCOFs with different geometries that cause their special physic-chemical properties, this review focuses on their high potential which has been exhibited in various applications in extraction and pre-concentration of different analytes such as organic compounds, heavy metal ions and biological samples. The article also highlights the applications of magnetic covalent organic frameworks in other chemical analysis such as adsorbent and being used in sensors.

Recent Advances in the Application of Covalent Organic Frameworks in Extraction: A Review

Covalent organic frameworks (COFs) are a class of emerging materials that are synthesized based on the covalent bonds between different building blocks. COFs possess unique attributes in terms of high porosity, tunable structure, ordered channels, easy modification, large surface area, and great physical and chemical stability. Due to these features, COFs have been extensively applied as adsorbents in various extraction modes. Enhanced extraction performance could be reached with modified COFs, where COFs are presented as composites with other materials including nanomaterials, carbon and its derivatives, silica, metal-organic frameworks, molecularly imprinted polymers, etc. This review article describes the recent advances, developments, and applications of COF-based materials being utilized as adsorbents in the extraction methods. The COFs, their properties, their synthesis approaches as well as their composite structures are reviewed. Most importantly, suggested mechanisms for the extraction of analyte(s) by COF-based materials are also discussed. Finally, the current challenges and future prospects of COF-based materials in extraction methods are summarized and considered in order to provide more insights into this field.

Facile synthesis of a novel magnetic covalent organic frameworks for extraction and determination of five fungicides in Chinese herbal medicines

A novel magnetic covalent organic framework was synthesized via one step coating approach with solvothermal reaction employing 2,4,6-tris(4-aminophen-yl)-1,3,5-triazine and 2,4,6-triformylphloroglucinol as two building blocks by covalent bonding. The prepared magnetic covalent organic frameworks were properly characterized by different techniques and employed as adsorbent of magnetic solid phase extraction. An analytical method was developed for simultaneous determination of five fungicides in two Chinese herbal medicine samples via magnetic solid phase extraction coupled to UHPLC-MS/MS analysis. Under optimized magnetic solid phase extraction conditions, the method exhibited satisfactory recoveries (74.0-109.6%) with the relative standard deviations of 0.4-4.6%, low limits of detection (0.003-0.015 μg kg^-1 ), and good linearity (R² > 0.9960). Compared with the traditional extraction method, the proposed method required a lower amount of adsorbent (3 mg) and extraction time (5 min). The adsorbent also had favourable reusability (not less than 8 times). Therefore, the magnetic covalent organic frameworks could be a promising adsorbent for the extraction and quantitation of pesticide residues in Chinese herbal medicines. This article is protected by copyright. All rights reserved.

Interface-Engineered Hollow Nanospheres with Titanium(IV) Binding Sites and Microwindows as Affinity Probes for Ultrafast and Enhanced Phosphopeptides Enrichment

Enrichment and identification of phosphopeptides in real biological samples are of great significance in many aspects. Herein, Ti⁴⁺-immobilized silica hollow nanospheres were tailored via chelating with phosphonic acid groups produced from dealkylation of phosphonate ester functionalized silica hollow nanospheres, which were synthesized through a single micelle templated method with diethylphosphatoethyltriethoxysilane (DPTES) and tetramethoxysilane (TMOS) as silane precursors under neutral conditions. The characterization results of transmission electron microscopy (TEM), nitrogen sorption isotherms, FT-IR, and energy-dispersive X-ray (EDX) spectroscopy confirmed the successful preparation of Ti⁴⁺-immobilized silica hollow nanospheres (SHS-Ti; approximately 17 nm particle size), which possessed a 10 nm hollow cavity with 1.6 nm micropores on the thin shell (about 3.5 nm). Attributed to the immobilized Ti⁴⁺ and high specific area (396 m²/g), SHS-Ti was applied as a Ti⁴⁺-immobilized metal affinity chromatography (Ti-IMAC) material and showed good specificity, a low limit of detection (5 fmol), high selectivity (tryptic digestion mixture of bovine serum albumin/β-casein, 1000:1 molar ratio), high binding capacity (120 mg/g for pyridoxal 5'-phosphate), and a high binding constant (1.30 × 10³ L/mg). Particularly, benefiting from the unique hollow structure with microwindows on the thin shell, a short transport path, and small mass transfer resistance, SHS-Ti exhibited excellent enrichment speed in which both phosphopeptide loading and elution could be completed in 1 min. The 5298 unique phosphopeptides from 1618 unique phosphoproteins were identified after enrichment by SHS-Ti from 100 μg Jurkat cell lysates within three independent replicates. The results showed that SHS-Ti could be utilized as a novel and promising enrichment probe for phosphopeptide characterization in MS-based phosphoproteomics and related fields.

Tailoring multifunctional magnetic cationic metal-organic framework composite for synchronous enrichment of phosphopeptides/glycopeptides

Herein, for the first time, a multifunctional magnetic cationic MOF composite (Fe3O4@ILI-01@Ti4+) was successfully prepared for the synchronous enrichment of phosphopeptides/glycopeptides. The as-prepared Fe3O4@ILI-01@Ti4+ bears attractive properties like abundant surface...

Design of a Spiropyran-Based Smart Adsorbent with Dual Response: Focusing on Highly Efficient Enrichment of Phosphopeptides

Smart responsive materials have attractive application prospects due to their tunable behaviors. In this work, we design novel spiropyran (SP)-based magnetic nanoparticles (MNP-SP) with dual response to ultraviolet light and pH and apply them to the enrichment of phosphopeptides. SP is modified on the surface of magnetic nanoparticles through a simple esterification reaction, based on which an MNP-SP-MS phosphopeptide identification platform is established. The capture and release of phosphopeptides are facilely adjusted by changing external light and the pH of the solution. The smart responsive MNP-SP has fast magnetic response performance, high sensitivity (detection limit of 0.4 fmol), and good reusability (6 cycles). In addition, MNP-SP is used for the enrichment of phosphopeptides in skimmed milk, human saliva, and human serum samples, indicating that it is an ideal adsorbent for enriching low-abundance phosphopeptides in complex biological environments.

Ionic Covalent Organic Frameworks for Energy Devices

Covalent organic frameworks (COFs) are a class of porous crystalline materials whose facile preparation, functionality, and modularity have led to their becoming powerful platforms for the development of molecular devices in many fields of (bio)engineering, such as energy storage, environmental remediation, drug delivery, and catalysis. In particular, ionic COFs (iCOFs) are highly useful for constructing energy devices, as their ionic functional groups can transport ions efficiently, and the nonlabile and highly ordered all-covalent pore structures of their backbones provide ideal pathways for long-term ionic transport under harsh electrochemical conditions. Here, current research progress on the use of iCOFs for energy devices, specifically lithium-based batteries and fuel cells, is reviewed in terms of iCOF backbone-design strategies, synthetic approaches, properties, engineering techniques, and applications. iCOFs are categorized as anionic COFs or cationic COFs, and how each of these types of iCOFs transport lithium ions, protons, or hydroxides is illustrated. Finally, the current challenges to and future opportunities for the utilization of iCOFs in energy devices are described. This review will therefore serve as a useful reference on state-of-the-art iCOF design and application strategies focusing on energy devices.

Removal of adsorption sites on the external surface of mesoporous adsorbent for eliminating the interference of proteins in enrichment of phosphopeptides/nucleotides

Various mesoporous adsorbents are of great promise for enriching small molecules from biological samples based on the size-exclusion effect. At present, the mesoporous adsorbents have adsorption sites distributed uniformly on the internal and external surfaces of mesopores. However, the adsorption sites on the external surface can adsorb proteins, interfering with the enrichment of small molecules. Herein, a novel immobilized-Ti⁴⁺ magnetic mesoporous adsorbent removing the adsorption sites on the external surface was facile prepared via the coupling chemistry of isocyanate with amine and consequent hydrolysis of urea linkage by urease. The adsorbent enables fast and selective enrichment of phosphopeptides and nucleotides from biological samples. In addition, sensitive detection methods for phosphopeptides and nucleotides in human serum are developed by coupling the magnetic solid-phase extraction with matrix-assisted laser desorption/ionization time of flight mass spectrometry and liquid chromatography-mass spectrometer, respectively. Under optimal conditions, response is linear (R² ≥ 0.9923), limits of detection are low (0.41-9.48 ng mL^-1), and reproducibility is acceptable (inter- and intra-day assay RSDs of≤15.0%) for six nucleotides. The developed strategy offers an effective method to eliminate the interference of proteins in the enrichment of small molecules from real biological samples.

An ionic covalent organic framework for rapid extraction of polar organic acids from environmental waters

An ionic covalent organic framework (Fe₃O₄@EB-TFB-iCOF) as a polar adsorbent was synthesized and characterized. It was applied in the magnetic solid phase extraction (MSPE) of four polar organic acids, namely, 2-(2,4,5-trichlorophenoxy)propionic acid, 2-methyl-4-chlorophenoxy acetic acid, naphthyloxyacetic acid, and naphthylacetic acid. The organic acids were detected by high performance liquid chromatography-ultraviolet analysis (HPLC-UV). A method for the determination of organic acids based on MSPE-HPLC-UV was established. The method shows good linear regression (R²≥ 0.9950), high precision (1.53-3.80%, n = 6), and low detection limit (0.10-0.49 ng mL^-1). The recovery rate of environmental water samples ranges from 73.3% to 101.0%. This method provides a possibility for high sensitivity analysis of polar organic acids.

A new Ti-based IMAC nanohybrid with high hydrophilicity and enhanced absorption capacity for the selective enrichment of phosphopeptides

Ti-based immobilized metal affinity chromatography (IMAC) nanomaterial has shown high potential in phosphoproteome mass-spectrometric (MS) analysis. However, the limited surface area and poor solubility will greatly restrict its use in phosphoproteome research. To overcome these two key drawbacks, a novel Ti-based IMAC nanomaterial was prepared by Ti-bonded β-cyclodextrin (β-CD) anchored on the surface of carbon nanotubes (CNTs) (denoted as COOH-CNTs-CD-Ti) and successfully applied as a biofunctional adsorbent for selectively enriching trace phosphopeptides. In the selective enrichment process, CNTs provided greater surface area for the absorption of phosphopeptides, while β-CD also offered a greater opportunity for the interaction between phosphopeptides and Ti⁴⁺. COOH-CNTs-CD-Ti with the aforementioned properities exhibited higher selectivity for phosphopeptides from the standard protein digests, the tryptic digests of nonfat milk and human serum, showing a great selective enrichment capability towards complex biological samples.

Facile mechanochemistry synthesis of magnetic covalent organic framework composites for efficient extraction of microcystins in lake water samples

Easy-preparation magnetic solid-phase extraction (MSPE) adsorbents with excellent extraction performance are very indispensable for MSPE techniques. Herein, a magnetic carbon nanotube covalent organic framework composite (MCNTs@TpPa-1) was prepared simply and rapidly through mechanochemical synthesis as MSPE adsorbent for enriching microcystins (MCs). The synthesized MCNTs@TpPa-1 exhibited well water dispersibility, high affinity with MCs and large surface area, resulting in outstanding extraction performance for MCs. Subsequently, combined with high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), an efficient, sensitive and convenient MSPE method was set up for the determination of trace MCs from aqueous sample, which exhibited acceptable repeatability (RSDs (relative standard deviations) ≤ 6.8%, n = 6), low limits of detection (LODs, 0.8-1.5 pg mL^-1), reliable linearity (R ≥ 0.9991) and broad range of linearity (2.0-1000 pg mL^-1). Furthermore, the developed method was applied to lake samples and trace MCs (9.6-24.6 pg mL^-1) were found with satisfactory recovery (85.0-106.0%). The results indicated powerfully MCNTs@TpPa-1 was of significant potential as an MSPE sorbent for detection of trace MCs in water. Moreover, considering the complexity of traditional preparation methods, novel prospects for preparing magnetic covalent organic frameworks (COFs) with excellent extraction properties were opened up.

Carnosine functionalized magnetic metal-organic framework nanocomposites for synergistic enrichment of phosphopeptides

Protein phosphorylation regulates the conformations and function of proteins, which plays an important part in organisms. However, systematic and in-depth analysis of phosphorylation often hinders on account of the low abundance and suppressed ionization of phosphopeptides. Various materials based on single enrichment mechanism show potential in phosphopeptides enrichment, but the enrichment performance is typically not satisfactory. Herein, we developed a carnosine (Car) functionalized magnetic metal organic framework designed as Fe₃O₄@NH₂@ZIF-90@Car. Benefiting from the multiple recognition groups of Car and massive metal ions site of ZIF-90, the as-fabricated Fe₃O₄@NH₂@ZIF-90@Car was utilized as a multifunctional material with synergistic effect for phosphopeptides enrichment. On the basis of combined immobilized metal ion affinity chromatography (IMAC) and amine-based affinity enrichment mechanism, Fe₃O₄@NH₂@ZIF-90@Car exhibited higher enrichment performance of phosphopeptides compared with Fe₃O₄@NH₂@ZIF-90 (single IMAC mechanism). Besides, the feasibility of Fe₃O₄@NH₂@ZIF-90@Car nanocomposites in complicated samples was further verified by enriching phosphopeptides from nonfat milk, human fluids such as serum and saliva, demonstrating its bright application prospects in phosphoproteomics analysis.

Advances in epitope molecularly imprinted polymers for protein detection: a review

Epitope molecularly imprinted polymers (EMIPs) are novel imprinted materials using short characteristic peptides as templates rather than entire proteins. To be specific, the amino acid sequence of the template peptide is the same as an exposed N- or C-terminus of a target protein, or its amino acid composition and sequence replicate a similar conformational arrangement as the same amino acid residues on the surface of the target protein. EMIPs have a good application prospect in protein research. Herein, we focus on classification of epitope imprinting techniques, methods of epitope immobilization on matrix materials including boronate affinity immobilization, covalent bonding immobilization, physical adsorption immobilization and metal ion chelation immobilization, and application of EMIPs in peptides, proteins, target imaging and target therapy fields. Finally, the main problems and future development are summarized.

Ionic covalent organic frameworks for the magnetic solid-phase extraction of perfluorinated compounds in environmental water samples

A novel magnetic ionic covalent organic framework (Fe₃O₄@EB-iCOFs) was designed and synthesized. It was then characterized by X-ray diffraction, N₂ adsorption-desorption analysis, and magnetic measurements, among others. The material shows the advantages of ionic property, large surface area, and magnetic responsiveness. It has potential of magnetic solid-phase extraction (MSPE) of perfluorinated compounds (PFCs). A method for the determination of PFCs based on MSPE-HPLC-MS/MS was established. The method has excellent linearity (r ≥ 0.995) in the working range 1-1000 ng L^-1 , good repeatability (1.4-5.8%, n = 6), low limits of detection in the range 0.1-0.8 ng L^-1 and satisfactory recoveries (between 73.9 and 108.3%).

Determination of trace bisphenols in functional beverages through the magnetic solid-phase extraction with MOF-COF composite

In this study, a novel porous composite (Fe₃O₄@TAPB-COF@ZIF-8) consisting of metal-organic and covalent organic frameworks was developed and applied to the magnetic solid-phase extraction (MSPE) of bisphenols. The extraction parameters such as the extraction time, solution pH, amounts of adsorbent, and ionic strength were investigated to obtain the best extraction conditions. By optimizing the MSPE, a convenient and sensitive analytical method was established in combination with high-performance liquid chromatography. The method achieved low detection limits (0.04-0.05 ng mL^-1), wide linear range (0.25-1000 ng mL^-1), good repeatability (1.20-4.30%), good reproducibility (1.34-4.03%), and satisfactory recoveries of four functional beverages (66.2-116.6%).

Nanoscale covalent organic frameworks as theranostic platforms for oncotherapy: synthesis, functionalization, and applications

Cancer nanomedicine is one of the most promising domains that has emerged in the continuing search for cancer diagnosis and treatment. The rapid development of nanomaterials and nanotechnology provide a vast array of materials for use in cancer nanomedicine. Among the various nanomaterials, covalent organic frameworks (COFs) are becoming an attractive class of upstarts owing to their high crystallinity, structural regularity, inherent porosity, extensive functionality, design flexibility, and good biocompatibility. In this comprehensive review, recent developments and key achievements of COFs are provided, including their structural design, synthesis methods, nanocrystallization, and functionalization strategies. Subsequently, a systematic overview of the potential oncotherapy applications achieved till date in the fast-growing field of COFs is provided with the aim to inspire further contributions and developments to this nascent but promising field. Finally, development opportunities, critical challenges, and some personal perspectives for COF-based cancer therapeutics are presented.

Effective enrichment and detection of trace polybrominated diphenyl ethers in water samples based on magnetic covalent organic framework nanospheres coupled with chromatography-mass spectrometry

Novel core shell structured magnetic covalent organic frameworks were synthesized at room temperature and first applied in water samples for the enrichment of trace polybrominated diphenyl ethers (PBDEs) through magnetic solid-phase extraction. The prepared materials were characterized through transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and X-ray photoelectron spectroscopy. During adsorption, the parameters affecting extraction and desorption efficiency were further optimized. Combined gas chromatography and mass spectrometry (GC/MS) revealed that high enrichment factors (275-292), low limits of detection (0.12-0.38 ng·L-1), wide linear ranges (0.5-1000 ng·L-1), and good reproducibility (intra-day 1.40%-4.31% and inter-day 5.14%-9.12%) were obtained under optimal conditions. The method successfully detected PBDEs in different water samples.