Enhancement of acidic lipid analysis by nanoflow ultrahigh performance liquid chromatography–mass spectrometry

Optimization of skin sampling based on tape stripping for lipidome analysis by nanoflow ultrahigh performance liquid chromatography-tandem mass spectrometry

In this study, skin sampling by tape stripping for lipid analysis was optimized by examining the lipid profiles of the stratum corneum (SC), focusing on the composition and levels of ceramides (Cer), diacylglycerols (DG), and triacylglycerols (TG), using nanoflow ultrahigh performance liquid chromatography-tandem mass spectrometry. Significant variations in the number and composition of the identified lipids, particularly Cer and neutral lipid species, were observed across different skin locations, including the forearm, forehead, cheek, and neck. Analysis of the layer-to-layer lipid profiles of the seven consecutive layers revealed a gradual decrease in DG and TG levels from the outermost to the innermost layers, with certain Cer subclasses showing increases in the second to fourth layers and subsequent decreases. Comparative analysis of lipid profiles from adjacent spots demonstrated statistical consistency and persistent differences between spots. Pooling layers were evaluated as an alternative method for representing SC layers, and their efficiencies were assessed by varying the number of pooled layers. We found that pooling five consecutive layers was effective in terms of the number and levels of identified lipids. Additionally, investigations into the matrix effect and extraction efficiency upon pooling layers indicated that pooling up to five layers did not significantly affect ionization suppression or reduce extraction recovery.

Improving the intestinal lipidome coverage in a gnotobiotic mouse model using UHPLC-MS-based approach through optimization of mobile phase modifiers and column selection

Lipidomics is focusing on the screening of lipid species in complex mixtures using mass spectrometry-based approaches. In this work, we aim to enhance the intestinal lipidome coverage within the Oligo-Mouse-Microbiota (OMM12) colonized mouse model by testing eight mobile phase conditions on five reversed-phase columns. Our selected mobile phase modifiers included two ammonium salts, two concentrations, and the addition of respective acids at 0.1 %. We compared two columns with hybrid surface technology, two with ethylene bridged hybrid technology and one with core-shell particles. Best performance was attained for standards and intestinal lipidome, using either ammonium formate or acetate in ESI(+) or ammonium acetate in ESI(-) for all column technologies. Notably, a concentration of 5 mM ammonium salt showed optimal results for both modes, while the addition of acids had a negligible effect on lipid ionization efficiency. The HST BEH C18 column improved peak width and tailing factor parameters compared to other technologies. We achieved the highest lipid count in colon and ileum content, including ceramides, phosphatidylethanolamines and phosphatidylcholines, when using 5 mM ammonium acetate in ESI(-). Conversely, in ESI(+) 5 mM ammonium formate demonstrated superior coverage for diacylglycerols and triacylglycerols.

Facile synthesis of amino-functionalized magnetic materials for efficient enrichment of anionic metabolites from biological samples

The analysis of biological samples is often affected by the background matrix. Proper sample preparation is a critical step in the analytical procedure for complex samples. In this study, a simple and efficient enrichment strategy based on Amino-functionalized Polymer-Magnetic MicroParticles (NH₂-PMMPs) with coral-like porous structures was developed to enable the detection of 320 anionic metabolites, providing detailed coverage of phosphorylation metabolism. Among them, 102 polar phosphate metabolites including nucleotides, cyclic nucleotides, sugar nucleotides, phosphate sugars, and phosphates, were enriched and identified from serum, tissues, and cells. Furthermore, the detection of 34 previously unknown polar phosphate metabolites in serum samples demonstrates the advantages of this efficient enrichment method for mass spectrometric analysis. The limit of detections (LODs) were between 0.02 and 4 nmol/L for most anionic metabolites and its high sensitivity enabled the detection of 36 polar anion metabolites from 10 cell equivalent samples. This study has provided a promising tool for the efficient enrichment and analysis of anionic metabolites in biological samples with high sensitivity and broad coverage, facilitating the knowledge of the phosphorylation processes of life.

Application of hybrid surface technology for improving sensitivity and peak shape of phosphorylated lipids such as phosphatidic acid and phosphatidylserine

The use of hybrid surface technology (HST), applied to the metal surfaces of an ACQUITY™ UPLC™ system and column, designed to mitigate the chelation, poor peak shape and analyte loss seen with acidic phospholipids was investigated. Compared to a conventional system significant improvements in both sensitivity, recovery and peak shape were obtained following UPLC on a CSH C18 column when the HST was used for the analysis of lysophosphatidic acid (LPA), phosphatidic acid (PA), lysophosphatidylserine (LPS), phosphatidylserine (PS), phosphatidylinositol-monophosphates (PIP), ceramide phosphate (CerP) and sphingoid base phosphate (SPBP). The benefits in chromatographic performance provided by the HST were seen particularly at low concentrations of these analytes. The HST system and column reduced peak tailing by 65-80% and peak width by 70-86% for LPA and PA. Moreover, increased signal intensities of up to 12.7 times were observed for LPA with the HST approach compared to the equivalent untreated LC system and column. The application of this methodology to the analysis of chicken egg PA and brain porcine PS extracts were accompanied by similar improvements in data quality.

A new update of MALDI-TOF mass spectrometry in lipid research

Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is an indispensable tool in modern lipid research since it is fast, sensitive, tolerates sample impurities and provides spectra without major analyte fragmentation. We will discuss some methodological aspects, the related ion-forming processes and the MALDI MS characteristics of the different lipid classes (with the focus on glycerophospholipids) and the progress, which was achieved during the last ten years. Particular attention will be given to quantitative aspects of MALDI MS since this is widely considered as the most serious drawback of the method. Although the detailed role of the matrix is not yet completely understood, it will be explicitly shown that the careful choice of the matrix is crucial (besides the careful evaluation of the positive and negative ion mass spectra) in order to be able to detect all lipid classes of interest. Two developments will be highlighted: spatially resolved Imaging MS is nowadays well established and the distribution of lipids in tissues merits increasing interest because lipids are readily detectable and represent ubiquitous compounds. It will also be shown that a combination of MALDI MS with thin-layer chromatography (TLC) enables a fast spatially resolved screening of an entire TLC plate which makes the method competitive with LC/MS.

Molecular mechanism associated with the use of magnetic fermentation in modulating the dietary lipid composition and nutritional quality of goat milk

Standard fermentation (SF) mainly affected the metabolism of glycerophospholipid and sphingolipid, and increased the total lipid content of goat milk. Content of total lipid was decreased by magnetic fermentation compared with SF, mainly due to triacylglycerol and diacylglycerol. Comprehensive characteristic of lipids dynamic changes during standard and magnetic fermentation was performed using high-throughput quantitative lipidomics. Totally, 488 lipid molecular species covering 12 subclasses were detected, and triacylglycerol was the highest levels, followed by diacylglycerol and phosphoethanolamine in the whole fermentation stage. Specifically, except for ceramide and simple Glc series, the content of all polar lipids in SF was dropped and neutral lipids subjoined. Compared with SF, the decrease of triacylglycerol (1752.47 to 784.78 μg/mL), diacylglycerol (60.36 to 24.89 μg/mL) and simple Glc series (4.36 to 2.40 μg/mL) were observed, while ceramide (6.54 to 25.87 μg/mL) increased, suggesting magnetic fermentation as effective approach to potentially improve the nutritional of goat milk.