Modifying superparamagnetic iron oxide and silica nanoparticles surfaces for efficient (MA)LDI-MS analyses of peptides and proteins

AuNPs/CNC Nanocomposite with A "Dual Dispersion" Effect for LDI-TOF MS Analysis of Intact Proteins in NSCLC Serum Exosomes

Detecting exosomal markers using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) is a novel approach for examining liquid biopsies of non-small cell lung cancer (NSCLC) samples. However, LDI-TOF MS is limited by low sensitivity and poor reproducibility when analyzing intact proteins directly. In this report, gold nanoparticles/cellulose nanocrystals (AuNPs/CNC) is introduced as the matrix for direct analysis of intact proteins in NSCLC serum exosomes. AuNPs/CNC with "dual dispersion" effects dispersed and stabilized AuNPs and improved ion inhibition effects caused by protein aggregation. These features increased the signal-to-noise ratio of [M+H]+ peaks by two orders of magnitude and lowered the detection limit of intact proteins to 0.01 mg mL-1. The coefficient of variation with or without AuNPs/CNC is measured as 10.2% and 32.5%, respectively. The excellent reproducibility yielded a linear relationship (y = 15.41x - 7.983, R2 = 0.989) over the protein concentration range of 0.01 to 20 mg mL-1. Finally, AuNPs/CNC-assisted LDI-TOF MS provides clinically relevant fingerprint information of exosomal proteins in NSCLC serum, and characteristic proteins S100 calcium-binding protein A10, Urokinase plasminogen activator surface receptor, Plasma protease C1 inhibitor, Tyrosine-protein kinase Fgr and Mannose-binding lectin associated serine protease 2 represented excellent predictive biomarkers of NSCLC risk.

User-friendly platform for analysis of high mass intact proteins and glycopeptides by laser desorption/ionization-mass spectrometry based on copper oxide particles

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) based on micro/nanostructured materials with different natures has received increasing attention for the analysis of a wide variety of analytes. However, up to now, only a few studies have shown the application of simple platforms in MALDI-MS for the identification of intact proteins. The present work reports on the application of copper oxide particles (Cu2O PS), obtained by a greener route, in combination with low amounts of 2,5-dihydroxybenzoic acid (DHB) as a novel hybrid platform. The combined Cu2O PS@DHB matrix, containing only 2.5 mg mL-1 of particles and 10 mg mL-1 of DHB, was easily applicable in MALDI-MS without surface modification of target plates. Under optimal conditions, the analysis of intact proteins up to 150,000 Da was possible, including immunoglobulin G, bovine serum albumin, and cytochrome C with adequate spot-to-spot signal reproducibility (RSD < 10%). In addition, the analysis of glycopeptides from IgG digests was carried out to prove the multipurpose application of the Cu2O PS@DHB platform in the low m/z range (2500-3000 Da). From the obtained results, it can be concluded that the optical and surface properties of as-synthesized Cu2O PS are likely to be responsible for the superior performance of Cu2O PS@DHB in comparison with conventional matrices. In this sense, the proposed user-friendly methodology opens up the prospect for possible implementation in bioanalysis and diagnostic research.

Preparation of core-shell MOF@MOF nanoparticle as matrix for the analysis of rhubarb anthraquinones in plasma by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A core-shell structure UiO-66-(OH)₂@UiO-66-NH₂ (MOF@MOF) nanoparticle was synthesized through a simple hydrothermal method and employed as an adsorbent and laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) matrix for the quantitative analysis of rhubarb anthraquinones (RAs). The properties of the materials were characterized by field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller. The results indicate that MOF@MOF is regular octahedral structure with a size distribution of about 100 nm, having large BET specific surface area (920 m²/g). Using the MOF@MOF as a matrix shows lower background interference, higher sensitivity, and better storage stability than that of traditional matrices. The MOF@MOF matrix exhibits excellent salt tolerance even under a NaCl concentration of 150 mM. Then, the enrichment conditions were optimized, and the adsorption time of 10 min, adsorption temperature of 40 °C and adsorbent amount of 100 μg were selected. In addition, the possible mechanism of MOF@MOF as an adsorbent and matrix was discussed. Finally, the MOF@MOF nanoparticle was employed as a matrix for the sensitive MALDI-TOF-MS analysis of RAs in spiked rabbit plasma, and the recoveries are in the range of 88.3-101.5% with RSD ≤9.9%. In short, the novel MOF@MOF matrix has demonstrated its potential in the analysis of small-molecule compounds in biological samples.