Core-shell structured magnetic covalent organic frameworks (FeO@COFs) were synthesized via a facile approach at room temperature. Combining the advantages of high porosity, magnetic responsiveness, chemical stability and selectivity, FeO@COFs can serve as an ideal absorbent for the highly efficient enrichment of peptides and the simultaneous exclusion of proteins from complex biological samples.

Core–shell structured Fe3O4@TbBd composite nanospheres were synthesised using a facile approach and successfully applied for selective enrichment of peptides with simultaneous exclusion of proteins.

Chemical modification of covalent organic frameworks (COFs) is indispensable for integrating functionalities of greater complexity and accessing advanced COF materials suitable for more potential applications. Reported here is a novel strategy for fabricating controllable core–shell structured Zr4+-immobilized magnetic COFs (MCNC@COF@Zr4+) composed of a high-magnetic-response magnetic colloid nanocrystal cluster (MCNC) core, Zr4+ ion-functionalized two-dimensional COFs as the shell by sequential postsynthetic functionalization and, for the first time, the application of the MCNC@COF@Zr4+ composites for efficient and selective enrichment of phosphopeptides. The as-prepared MCNC@COF@Zr4+ composites possess regular porosity with large surface areas, high Zr4+ loading amount, strong magnetic responsiveness, and good thermal/chemical stability, which can serve as an ideal adsorbent for selective enrichment of phosphopeptides and simultaneous size exclusion of biomacromolecules, such as proteins. The high detection sensitivity (10 fmol) together with the excellent recovery of phosphopeptides is also obtained. These outstanding features suggest that the MCNC@COF@Zr4+ composites are of great benefit for pretreatment prior to mass spectrometry analysis of phosphopeptides. In addition, the performance of the developed approach in selective enrichment of phosphopeptides from the tryptic digests of defatted milk and directly specific capture of endogenous phosphopeptides from human serum gives powerful proof for its high selectivity and effectiveness in identifying the low-abundance phosphopeptides from complicated biological samples. This study not only provides a strategy for versatile functionalization of magnetic COFs but also opens a new avenue in their use in phosphoproteome analysis.

Mass spectrometry (MS)-based in-depth glycoproteomics demands additional sample pretreatment to remove interference from nonglycoproteins and to enhance the precise identification of low-abundance glycopeptides. Herein, an attractive strategy was proposed for preparing core−shell-structured phenylboronic acid-immobilized magnetic covalent organic frameworks (MCNCs@COF@PBA), which were comprised of magnetite colloid nanocrystal clusters (MCNCs) adopted as a core and phenylboronic acid-modified covalent organic frameworks (COFs) served as the shell via a facile azide−alkyne "click" reaction and the first application in the specific enrichment of N-linked glycopeptides. The resultant MCNCs@COF@PBA composites exhibited high magnetic responsiveness, uniform mesoporous structure, and high surface area, as well as abundant binding sites, which could act as an efficient adsorbent for specific capture of the N-linked glycopeptides from the digested glycoprotein and protein mixture along with simultaneous protein repelling. These results confirmed that the MCNCs@COF@PBA composites had some distinct advantages in the enrichment of the N-linked glycopeptides, which included outstanding selectivity (HRP:BSA = 1:600), good sensitivity (100 amol), high enrichment recovery (∼93% ± 3%) and rapid magnetic separation (∼1 min). Furthermore, the developed MCNCs@COF@PBA-based MS method could be successfully applied to analyze glycopeptides in exosomes secreted from HeLa cell. This study not only provides a potential selective enrichment platform for comprehensive N-glycoproteome profiling, but also opens up a new avenue for universal functionalization of COFs-based materials.

Mass spectrometry imaging (MSI) techniques make possible the spatial chemical identification of analytes, especially for biological samples. As a universal energy source, laser is one of the most commonly used sampling methods in MSI techniques. However, due to the limitation of laser spot size, subcellular spatial resolution imaging, which is significant for life science researches, always remains a challenge for laser-based MSI. In this research, we designed a laser ablation (LA) system with a microlensed fiber and a "three-way" structure ablation chamber, and achieved nanoscale inductively coupled plasma (ICP) MSI with an adjustable spatial resolution down to 400 nm, which surpasses most existing technologies. With this device, the distribution of various photodynamic therapy drugs in the intestine of mouse can be clearly observed. The comparison imaging results showed that the drug distribution in tissue slice could be identified at the subcellular level with the high-resolution mode. More valuably, gold nanorods (GNRs) and carboplatin in a single cell are able to be visualized at organelle level due to the nanoscale resolution, which is able to reveal the mechanism of cell apoptosis. This reliable and economical MSI technique is expected to be used in understanding the precise chemical composition and transportation in small tissues, microorganisms, and single cells.

A nano laser probe based double-pulse LIBS technique achieves nanoscale elemental imaging with a 500 nm resolution.

Surface-assisted laser desorption/ionization (SALDI) acts as a soft desorption/ionization technique, which has been widely recognized in small-molecule analysis owing to eliminating the requirement of the organic matrix. Herein, titania nanosheets (TiO2 NSs) were applied as novel substrates for simultaneous analysis and imaging of low-mass molecules and lipid species. A wide variety of representative analytes containing amino acids, bases, drugs, peptides, endogenous small molecules, and saccharide-spiked urine were examined by the TiO2 NS-assisted LDI mass spectrometry (MS). Compared with conventional organic matrices and substrates [Ag nanoparticles (NPs), Au NPs, carbon nanotubes, carbon NPs, CeO2 microparticles, and P25 TiO2], the TiO2 NS-assisted LDI MS method shows higher sensitivity and less spectral interference. Repeatability was evaluated with batch-to-batch relative standard deviations for 5-hydroxytryptophan, glucose-spiked urine, and glucose with addition of internal standard, which were 17.4, 14.9, and 2.8%, respectively. The TiO2 NS-assisted LDI MS method also allows the determination of blood glucose levels in mouse serum with a linear range of 0.5–10 mM. Owing to the nanoscale size and uniform deposition of the TiO2 NS matrix, spatial distributions of 16 endogenous small molecules and 16 lipid species from the horizontal section of the mouse brain tissue can be visualized at a 50 μm spatial resolution. These successful applications confirm that the TiO2-assisted LDI MS method has promising prospects in the field of life science.

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