Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is an excellent analytical technique for rapid and sensitive analysis of macromolecules such as polymers ...and proteins. However, the main drawback of MALDI‐TOF MS is its difficulty to detect small molecules with mass below 700 Da because of the intensive interference from MALDI matrix in the low mass region. In recent years there has been considerable interest in developing matrix‐free laser desorption/ionization by using nanostructured substrates to substitute the conventional organic matrices, which is often referred as surface‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (SALDI‐TOF MS). Despite these attractive features, most of the current SALDI‐TOF MS for the analysis of small molecules employ positive ion mode, which is subjected to produce multiple alkali metal adducts, and thus increases the complexity of the analysis. Different from the complicated adducts produced in positive ion mode, mass spectra obtained in negative ion mode are featured by deprotonated ion peaks without matrix interference, which simplifies the interpretation of mass spectra and detection of unknown. In this review, we critically survey recent advances in nanostructured substrates for negative ion LDI‐TOF MS analysis of small molecules in the last 5 years. Special emphasis is placed on the preparation of the nanostructured substrates and the results achieved in negative ion SALDI‐MS. In addition, a variety of promising applications including environmental, biological, and clinical analysis are introduced. The ionization mechanism of negative ionization is briefly discussed.
Highly efficient extraction of phospho- and glycopeptides from complicated biological samples is extremely crucial for comprehensive characterization of protein phosphorylation and glycosylation ...based on mass spectrometry (MS). In this work, a new synergistic strategy that combined surface covalent modification and alkaline etching was developed to synthesize hydrophilic hollow zirconium-organic frameworks (HHZr-MOFs) for simultaneous recognition and capture of phospho- and N-glycopeptides. The unique properties including high specific surface area, mesoporous shell and hollow cavity endowed HHZr-MOFs with facilitated mass transport and abundant accessible active sites. Benefited from the maltose modified on the external surface and Zr–O clusters retained on the internal surface, HHZr-MOFs could act as a highly efficient bifunctional probe for simultaneous enrichment of phospho- and N-glycopeptides based on hydrophilic interaction chromatography (HILIC) and metal oxide affinity chromatography (MOAC), respectively. Finally, a total of 98 endogenous phosphopeptides and 216 endogenous N-glycopeptides were simultaneously captured by HHZr-MOFs from saliva samples of patients with oral inflammation, and several phospho- and glycoproteins related with coagulation, bacterial defense and immune response for oral inflammation were identified by Gene ontology (GO) analyses, confirming the great potential of HHZr-MOFs in rapid detection of clinical biomarkers and comprehensive profiling of phosphoproteomic and glycoproteomic for complex biological samples. This work not only provides an alternative method to precisely design and synthesize sophisticated hollow MOFs with multifunctionalities, but also offers a novel concept of multifunctional material design for bioseparation and analysis in modification-specific proteomics.
Hydrophilic hollow-structured Zr-MOFs (HHZr-MOFs) were synthesized via a synergistic strategy combining surface covalent modification and alkaline etching. Benefited from the coexistence of maltose on the external surface and Zr–O clusters on the internal surface, HHZr-MOFs could act as a highly efficient bifunctional probe for simultaneous enrichment of endogenous phospho- and N-glycopeptides from human saliva sample. Display omitted
•Hydrophilic hollow Zr-MOFs were synthesized by a synergistic strategy.•HHZr-MOFs possessed high surface area, mesoporous shell and hollow cavity.•HHZr-MOFs exhibited high selectivity towards phospho- and N-glycopeptides.•HHZr-MOFs could be applied to phospho- and glycoproteomic profiling of human saliva.
This work reports a novel metal-organic framework (MOF)-based metal affinity platform for the rapid and highly specific separation of histidine-rich proteins using zeolitic imidazolate framework-8 ...coated magnetic nanocomposites (denoted as Fe
O
@ZIF-8). The coating of the ZIF-8 layer on the Fe
O
core was performed in aqueous solution at room temperature and merely took 10 minutes. The monodisperse Fe
O
@ZIF-8 has an average diameter of 190 nm, displays superparamagnetism with a saturation magnetization value of 47.9 emu g
, and possesses a large external surface area of 131.0 m
g
. Due to the high density of low-coordinated Zn atoms on the surface of ZIF-8, Fe
O
@ZIF-8 exhibited a large adsorption capacity for model histidine-rich proteins (>6000 mg g
for bovine hemoglobin) and relatively low adsorption capacities for other proteins which contain fewer surface-exposed histidine residues. Moreover, Fe
O
@ZIF-8 showed excellent recyclability (more than 10 times) with high recovery (88.4%). In addition, Fe
O
@ZIF-8 can be used to selectively separate hemoglobin from a protein mixture and human blood samples. The good results demonstrate the potential of Fe
O
@ZIF-8 in the separation of histidine-rich proteins.
In this work, core-shell structured Ti4+-immobilized magnetic covalent organic frameworks (denoted as Fe3O4@TAPTDHTA-Ti4+ composites) were prepared for enhanced phosphopeptide enrichment by one-pot ...synthesis of COFs shell with inherent bifunctional groups on Fe3O4 NPs and further Ti4+ immobilization. The widely distributed bifunctional groups could provide abundant chelating sites for Ti4+ immobilizing. Combining with the high specific surface area and mesoporous structure, the Fe3O4@TAPTDHTA-Ti4+ composites exhibited excellent enrichment efficiency for phosphopeptides, such as low detection limit (0.05 fmol μL−1), high selectivity (1:5000 of molar ratio of β-casein/bovine serum albumin (BSA) tryptic digests), high adsorption capacity (62.9 μg mg−1) and strong size-exclusive effect (1:250:250 of molar ratio of β-casein tryptic digest/β-casein/BSA). In addition, this method was general for immobilizing other metal ions (Zr4+ and Fe3+). Notably, the Fe3O4@TAPTDHTA-Fe3+ composites exhibited controllable affinity towards mono-phosphopeptides and multi-phosphopeptides. Furthermore, the Fe3O4@TAPTDHTA-Ti4+ composites were successfully applied to selectively capture phosphopeptides from complex biological samples including the tryptic digest of nonfat milk, human serum and human saliva. More significantly, 3333 phosphopeptides derived from 1409 phosphoproteins with 3492 phosphorylation sites were clearly identified from the tryptic digest of HeLa cell lysate. In addition to providing a potential excellent enrichment probe for comprehensive phosphoproteomic analysis, this study also offers a new perspective for the functionalization of COFs.
Core-shell structured Ti4+-immobilized magnetic COFs (denoted as Fe3O4@TAPTDHTA-Ti4+ composites) were simply synthesized by one-pot synthesis of COFs shell with inherent bifunctional groups on Fe3O4 NPs and further Ti4+ immobilization and applied for enhanced phosphopeptide enrichment. Display omitted
•Magnetic IMAC-based COFs were simply synthesized.•The widely distributed bifunctional groups in COFs could load high amount of Ti4+.•Magnetic IMAC-based COFs exhibited enhanced enrichment performance towards phosphopeptides.•This enrichment probe could capture phosphopeptides from complex biological samples.
Surface imprinting over nanostructured matrices is an effective solution to overcome template removal and achieve high binding capacity. In this work, a facile method was developed for synthesis of ...polydopamine-coated molecularly imprinted silica nanoparticles (PDA-coated MIP silica NPs) based on self-polymerization of dopamine (DA) on the surface of silica NPs in the presence of template protein. Transmission electronic microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed that PDA layers were successfully attached on the surface of silica NPs and the corresponding thickness was about 5nm, which enabled the MIP silica NPs to have fast binding kinetics and high binding capacity. Under the aqueous media, the imprinted silica NPs showed much higher binding affinity toward template than non-imprinted (NIP) silica NPs. The protein recognition properties were examined by single-protein or competitive batch rebinding experiments and rebinding kinetics study, validating that the imprinted silica NPs have high selectivity for the template. The resultant BHb–MIP silica NPs could not only selectively separate BHb from the protein mixture, but also specifically deplete high-abundance BHb from cattle whole blood. In addition, the stability and regeneration were also investigated, which indicated that the imprinted silica NPs had excellent reusability.
•A facile method was developed for synthesis of PDA-coated protein-imprinted silica NPs.•The imprinted silica NPs showed large binding capacity and high selectivity toward template.•The imprinted silica NPs can be applied to the depletion of high-abundance BHb from cattle blood.
In the past few years, the immobilization of biomolecules on hybrid nanoflowers and metal-organic frameworks (MOFs)
via
self-assembly synthesis has received much attention due to its simplicity, high ...efficiency, and a bright prospect of enhancing the stability, activity and even selectivity of biomolecules compared to conventional immobilization methods. In the synthesis of organic-inorganic hybrid nanoflowers, biomolecules used as organic components are simply mixed with metal ions which act as inorganic components to form flower-like nanocomposites, while in the self-assembly process of encapsulating biomolecules in MOFs (biomolecule@MOF composites), the biomolecules just need to be added to the precursor mixtures of MOFs, in which the biomolecules are therefore embedded in MOF crystals with small pores. In this review, we focus on the recent advances of these composites, especially in the synthesis strategies, mechanism and applications in biosensors, biomedicine, pollutant disposal, and industrial biocatalysis, and future perspectives are discussed as well.
In the past few years, the immobilization of biomolecules on hybrid nanoflowers and metal-organic frameworks (MOFs)
via
self-assembly synthesis has received much attention due to its superior advantages.
Recently, research on and the application of nanomaterials such as graphene, carbon nanotubes, and metal-organic frameworks has become increasingly popular in tissue engineering. In 2014, a ...two-dimensional sheet of black phosphorus (BP) was isolated from massive BP crystals. Since then, BP has attracted significant attention as an emerging nanomaterial. BP possesses many advantages such as light responsiveness, electrical conductivity, degradability, and good biocompatibility. Thus, it has broad prospects in biomedical applications. Moreover, BP is composed of phosphorus, which is a key bone tissue component with good biocompatibility and osteogenic repair ability. Thereby, BP exhibits excellent advantages for application in bone tissue engineering. In this review, the structure and the physical and chemical properties of BP are described. In addition, the current applications of BP in bone tissue engineering are reviewed to aid the future research and application of BP.
•A facile approach was developed for preparation of glycoprotein-imprinted monolithic column.•The as-prepared imprinted monolith showed high affinity toward template glycoprotein.•It was successfully ...applied to the selective enrichment of HRP from human serum sample.
A novel imprinting strategy using reversible covalent complexation of glycoprotein was described for creating glycoprotein-specific recognition cavities on boronate-functionalized monolithic column. Based on it, a molecularly imprinted monolithic column was prepared by self-polymerization of dopamine (DA) on the surface of 4-vinylphenylboronic acid (VPBA)-based polymeric skeletons after reversible immobilization of horseradish peroxidase (HRP). Due to the combination of boronate affinity and surface imprinting of DA, the stable and accessible recognition sites in the as-prepared imprinted monolith could be obtained after the removal of the template, which facilitated the rebinding of the template and provided good reproducibility and lifetime of use. The recognition behaviors of proteins on the bare VPBA-based, HRP-imprinted and nonimprinted monolithic columns were evaluated in detail and the results showed that the HRP-imprinted monolith exhibited higher recognition ability toward the template than another two monolithic columns. Not only nonglycoproteins but also glycoproteins can be well separated with the HRP-imprinted monolith. In addition, the feasibility of the HRP-imprinted monolith, adopted as an in-tube solid phase microextraction (in-tube SPME), was further assessed by selective extraction and enrichment of HRP from human serum. The good results demonstrated its potential in glycoproteome analysis.
•Hydrophilic magnetic mesoporous nanoparticles were synthesized via click chemistry.•The mesoporous nanoparticles showed high hydrophilicity and large surface area.•Successful application to the ...selective enrichment of glycopeptides from protein digests.•Successful application to the selective enrichment of glycans from digested human serum.
Selective enrichment of glycopeptides from complex biological samples is essential for MS-based glycoproteomics, but challenges still remain. In this work, glucose-functionalized magnetic mesoporous nanoparticles (MMNs), which hold the attractive features of well-defined core/shell structure, high specific surface area (324m2/g), narrow pore size distribution (2.2nm) and high magnetic responsivity (69.1emug−1), were synthesized via click chemistry and applied to enrich glycopeptides and glycans. Taking advantages of the size-exclusive effect of mesopore against proteins and the hydrophilic interaction between glycans and glucose, the hydrophilic MMNs possessed high selectivity for glycopeptides at the digested mixtures of horseradish peroxidase (HRP), myoglobin and β-casein at molar ratio of 1:1:10, large enrichment capacity (as high as 250mg/g), high sensitivity (50fmol), excellent speed (5min for enrichment) and high recovery of glycopeptides (as high as 94.6%). Additionally, the MMNs exhibited excellent performance in enrichment of N-linked glycans from the digested human serum that are made up of peptides, large proteins and other compounds. These outstanding features will give the hydrophilic MMNs high benefit for MS analysis of low-abundance glycopeptides/glycans.
•A novel silica-UIO-66 composite was synthesized for liquid chromatographic stationary phase.•Fast separation of ethylbenzene and styrene was achieved with the packed column.•Baseline separation of ...positional isomers was achieved with the packed column.
A silica-UIO-66 composite was fabricated by a simple hydrothermal method and then applied as liquid chromatographic stationary phase for fast and efficient separation. X-ray diffraction patterns showed the presence of UIO-66 crystals in the silica-UIO-66 composites; while scanning electron microscope (SEM) images revealed that silica-UIO-66 composites were a homogeneous mixture of silica bead and UIO-66 crystals. A variety of substituted aromatics, chlorobenzene compounds and polycyclic aromatic hydrocarbons (PAHs) were used to evaluate the retention properties of the silica-UIO-66 composite packed column. Under the optimized conditions, baseline separation of ethylbenzene (EB) and styrene was obtained with high resolution and short retention time. In addition, the silica-UIO-66 composite packed column also showed some advantages in separation of positional isomers, with which baseline separation of EB and xylene, chlorotoluene and dichlorobenzene isomers was achieved. Moreover, the retention mechanisms of these compounds were also discussed in detail. The relative standard deviations (RSDs) for the separation of EB and xylene, chlorotoluene and dichlorobenzene isomers, as well as EB and styrene were 0.42–0.9%, 1.0–1.9%, 0.75–2.0%, and 0.9–2.1% for the retention time, peak area, peak height, and half peak width, respectively. The column efficiencies for EB, p-chlorotoluene, p-dichlorobenzene and styrene were 8780, 9060, 9990 and 5130 plates/m. The successful applications suggested high potentials of silica-MOFs composite as stationary phase for fast and efficient liquid chromatography separation.
