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High-throughput metabolic analysis based on laser desorption/ionization mass spectrometry exhibits broad prospects in the field of large-scale precise medicine, for which the assisted ionization ability of the matrix becomes a determining step. In this work, the gold-decorated hierarchical metal oxide heterojunctions (dubbed Au/HMOHs) are proposed as a matrix for extracting urine metabolic fingerprints (UMFs) of primary nephrotic syndrome (PNS). The hierarchical heterojunctions are simply derived from metal-organic framework (MOF)-on-MOF hybrids, and the native built-in electric field from heterojunctions plus the extra Au decoration provides remarkable ionization efficiency, attaining high-quality UMFs. These UMFs are employed to realize precise diagnosis, subtype classification, and effective prognosis evaluation of PNS by appropriate machine learning, all with 100% accurate ratios. Moreover, a high-confidence marker panel for PNS diagnosis is constructed. Interestingly, all panel metabolite markers present obviously uniform downregulation in PNS compared to healthy controls, shedding light on mechanism exploration and pathway analysis. This work drives the application of metabolomics toward precision medicine.

Human serum is a huge bioinformatics database of human physiological and pathological state, many proteins/peptides among which can serve as biomarkers for monitoring human's health condition, thereby being worth exploring. The simple and fast capture of biomarkers from human serum is the first key step to realize their accurate detection. In this work, we developed the aptamer functionalized magnetic metal organic framework nanoprobe, and furtherly combined with mass spectrometry technology to establish an efficient method of identifying biomarkers. Taking insulin as example of biomarker in human serum, we developed sulfhydryl human insulin aptamer functionalized magnetic metal organic framework (denoted as Mag MOF@Au@HIA) through the post-synthetic modification of MIL-101(Cr)–NH2 for testing the applicability of the established method. Depending on the strong magnetic responsiveness and high specific area as well as high-loaded human insulin aptamers, the limit of detection of insulin was down to 1 ng/mL and 2 ng/mL in the standard insulin solution and human serum, respectively. Moreover, a good linear relationship (R2 = 0.998) was obtained by using standard insulin solution with concentration range from 100 ng/mL to 5 ng/mL, based on which the capture recovery of insulin with Mag MOF@Au@HIA from human serum was demonstrated to be excellent. All of the results indicate that the aptamer-functionalized magnetic metal organic framework is a promising nanoprobe for biomarkers capture in human serum.

A mercaptosuccinic acid functionalized hydrophilic magnetic metal-organic framework nanocomposite (denoted as mMOF@Au-MSA) was proposed and synthesized to provide an excellent platform for glycopeptide analysis. The novel nanomaterial integrated favorable advantages such as robust magnetic response from Fe3O4 magnetic nanoparticles, large surface area contributed by MOF, abundant ultra-high hydrophilic carboxylic groups from mercaptosuccinic acid, as well as unbiased affinity toward different types of glycopeptides. This nanocomposite was successfully utilized to capture glycopeptides from standard protein digests with the high selectivity and great sensitivity of 0.5 fmol μL−1. Notably, 307 glycopeptides assigned to 96 glycoproteins were identified from only 2 μL serum of breast cancer patient. The satisfying achievement indicated that the as-prepared nanopartical had promising potential in exploring the knowledge of glycoproteins in breast cancer.

A hydrophilic probe is employed to enrich exosomes from three kinds of cancer cells by TiO2-phosphate interaction and exosomal glycoproteins by hydrophilic interaction in succession. The probe performs efficiently in both the enrichment processes. And the analytical results confirm that unique exosomal glycoproteins can distinguish parent exosomes from others.

A hydrophilic carbohydrate functionalized magnetic metal organic framework (Mag Zr-MOF@G6P) was synthesized via a facile one-step modification strategy for selective glycopeptide capture in virtue of hydrophilic interaction chromatography technique. The inherently hydrophilic Zr-MOF layer not only provides selective size-sieving pore structures but also offers large specific surface area to afford abundant affinity sites. Hydroxyl-rich glucose-6-phosphate was immobilized onto the Zr-MOF via a straightforward coordination manner to regulate its surface property, for the purpose of enhancing its hydrophilicity. Benefitting from the merits of Zr-MOF and glucose-6-phosphate, the as-designed composite exhibits good selectivity (the mass ratio of HRP digests to BSA digests was up to1:200) and low limit of detection (0.1 fmol μL−1) towards the recognition of glycopeptides from standard samples. More excitingly, glycopeptides in urine of healthy people and patients with kidney cancer were successfully enriched and identified by the combined liquid chromatography-mass spectrometry/mass spectrometry technology (LC-MS/MS). Further gene ontology analysis of molecular function and biological process revealed that 13 original glycoproteins of the identified glycopeptides from urine of patients significantly participate in diverse cancer-associated events, including collagen binding, immunoglobulin receptor binding, antigen binding, and complement activation process.

For the first time, dual metal ions (Ti4+-Zr4+) were successfully modified into the channel of magnetic mesoporous silica to obtain an affinity probe for highly selective capture of endogenous phosphopeptides in biological samples. The newly prepared Fe3O4@mSiO2@Ti4+-Zr4+ composites possessed the advantages of ordered mesoporous channels, superparamagnetism, and enhanced affinity properties of dual metal ions of Ti4+ and Zr4+. The phosphopeptide enrichment efficiency of the Fe3O4@mSiO2@Ti4+-Zr4+ composite was investigated, and the result indicated an ultrahigh size exclusive ability (weight ratio of β-casein tryptic digests, BSA, and α-casein protein reached up to 1:1000:1000). Compared to magnetic affinity probes with single metal ions (Fe3O4@mSiO2@Ti4+, Fe3O4@mSiO2@Zr4+), the composite possessed stronger specificity, higher sensitivity, and better efficiency; and more importantly, it showed much enhanced enrichment ability towards both mono- and multi-phosphorylated peptides. Additionally, by utilizing the Fe3O4@mSiO2@Ti4+-Zr4+ affinity probe, a total number of 104 endogenous phosphopeptides including 95 mono-phosphopeptides and 9 multi-phosphopeptides were captured and identified from human saliva, indicating the great potential for the application of the novel probe for the peptidome analysis in the future.

Peptidomics research is of great significance for discovering potential biomarkers and monitoring human diseases. As a kind of common clinical biofluid, saliva known for its noninvasive collection and easy accessibility has been widely used in peptidomics research. In this article, we combined immobilized metal ions affinity chromotography (IMAC) with mesoporous material and proposed the copper ion doped magnetic mesoporous silica material (denoted as Fe3O4@mSiO2-Cu2+) which had a large surface area of 221 m2 g−1 and pore volume of 0.20 cm3 g−1. By immobilizing copper ions onto the mesopore walls, the standard peptide Angiotensin II could be identified in an extremely low concentration of 0.1 fmol μl−1 and in a mass ratio of 1:500 (Angiotensin II:BSA, m/m), which indicated significant sensitivity and a great size-exclusive ability. In addition, the introduction of polydopamine (PDA) made Fe3O4@mSiO2-Cu2+ more hydrophilic and biocompatible which could improve the profiling of endogenous peptides in bio-sample. Finally, 131 endogenous peptides were identified in human saliva after enrichment with Fe3O4@mSiO2-Cu2+. Therefore, Fe3O4@mSiO2-Cu2+ nanoparticles provided a promising candidate protocol for biomarker discovery.

A facile and mild approach was carried out to synthesize citrate acid-magnetic ferroferric oxide for glycopeptide analysis. The material was synthesized successfully and applied in glycopeptide identification from human saliva, indicating that this method could be a promising tool for glycopeptidome analysis, which also enlightened the simple fabrication of hydrophilic materials in analytical science.

As the lower-molecular-weight subset of proteome, the peptidome has attracted increasing attention in recent years due to the simple usability of sample (without digestion) and great potential in acting as diagnostic biomarkers for many diseases. However, the relative low abundance of endogenous peptides and serious interferences from large-size proteins and salts in practical biosamples results in that it is seriously difficult to directly conduct mass spectrometry identification of endogenous peptides. Nanoporous materials such as mesoporous materials and metal organic framework materials are most popularly used for sample pre-treatment in peptidomics research, since their unique porous structures can exert size-exclusion effect that prevents the large-size proteins from entering into the porous channels while adopting the opposite attitude for small-size endogenous peptides. In this review, recent advances in nanoporous materials for sample preparation, including the enrichment of common endogenous peptides, endogenous phosphopeptides and glycopeptides are summarized and discussed comprehensively. Moreover, the concerns regarding the synthesis of nanoporous materials and enrichment biases of different functionalized nanoporous materials towards different targeted endogenous peptides are also discussed.

A capillary zone electrophoresis method (CZE) for the simultaneous determination of loureirin A and loureirin B was developed based on the optimized conditions of the pH, composition and concentration of the running buffer solution. Loureirin A and loureirin B were separated and determined effectively within 15 min in a running buffer solution of 20 mmol/L Na2B4O7 (pH 9.98 adjusted with NaOH solution) containing 10.0% (v/v) acetonitrile, 5.0% (v/v) ethylene glycol and 1.0% (v/v) butanol, with the applied voltage of 20 kV, capillary temperature of 25 degrees C, detection wavelength of 211 nm, and injection of 5 s at 3447 Pa. The linear ranges for the determination of loureirin A and loureirin B were 1.00-100 mg/L and 0.50-100 mg/L, respectively. The determination of loureirin A and loureirin B in dragon's blood from natural and artificial inoculation was performed by the proposed method. The relative standard deviations for the determination of the two constituents in samples were from 0.6% to 3.8%, and the recoveries ranged between 95.1% and 105.8%. The method is simple, rapid and possesses higher reproducibility and efficiency. It can be used for the determination of loureirin A and loureirin B in dragon's blood.

A capillary zone electrophoresis method (CZE) for the simultaneous determination of loureirin A and loureirin B was developed based on the optimized conditions of the pH, composition and concentration of the running buffer solution. Loureirin A and loureirin B were separated and determined effectively within 15 min in a running buffer solution of 20 mmol/L Na2B4O7 (pH 9.98 adjusted with NaOH solution) containing 10.0% (v/v) acetonitrile, 5.0% (v/v) ethylene glycol and 1.0% (v/v) butanol, with the applied voltage of 20 kV, capillary temperature of 25 degrees C, detection wavelength of 211 nm, and injection of 5 s at 3447 Pa. The linear ranges for the determination of loureirin A and loureirin B were 1.00-100 mg/L and 0.50-100 mg/L, respectively. The determination of loureirin A and loureirin B in dragon's blood from natural and artificial inoculation was performed by the proposed method. The relative standard deviations for the determination of the two constituents in samples were from 0.6% to 3.8%, and the recoveries ranged between 95.1% and 105.8%. The method is simple, rapid and possesses higher reproducibility and efficiency. It can be used for the determination of loureirin A and loureirin B in dragon's blood.

A method for the separation and determination of optical isomers of phenylephrine was developed based on the promoting effect of non-chiral ionic liquid on chiral ligand-exchange capillary electrophoresis after the electrophoretic parameters were optimized systematically. R-phenylephrine and S-phenylephrine can be separated and determined effectively in 20 mmol/L Tris-H3PO4 buffer solution (pH 5.4) composed of 4.0 mmol/L Cu(II), 8.0 mmol/L L-proline (L-Pro) and 15 mmol/L 1-butyl-3-methylimidazolium chloride ([BMIM] Cl) with the applied voltage of 20 kV, capillary temperature of 25 °C , detection wavelength of 254 nm, and injection of 5 s at 3,447 Pa. The resolution of R- and S-phenylephrines was 1. 42. The linear ranges for the determination of R-phenylephrine and S-phenylephrine were 12. 5 - 150 mg/L and 15. 0-150 mg/L, respectively. The method has been satisfactorily used for the determination of R-phenylephrine and S-phenylephrine in the spiked blood and urine samples. The spiked recoveries in the urine sample were in the range of 93. 7% -108. 2% with the RSDs lower than 3. 18% (n= 3) , and the spiked recoveries in the blood sample were in the range of 91. 4% and 113. 1% with the RSDs lower than 4. 82% (n =3).