Browsing by Author "López López, Ángeles"

Great advances in lipidomics during the last years have opened the door to a broader knowledge of oxygenated lipids. These substances are derived either from the inclusion of previously hydroxylated fatty acids in the lipid structure of sphingolipids and acyl-L-carnitines, or by enzymatic and nonenzymatic modifications (oxidized lipids) of glycerophospholipids (including cardiolipins), cholesteryl esters and cholesterol. Despite their significance in the regulation of multiple diseases such as cancer or diabetes, the number of experimentally detected oxygenated lipids remains relatively low. This is in part due to the main challenges in their analysis, which are their low natural concentrations, their wide diversity of physicochemical properties, presence of isomers, and their a priori unknown presence in the biological samples. In particular, analysis of oxidized lipids, especially peroxides, has become a daunting task in liquid chromatography coupled to mass spectrometry (LC-MS) due to their high chemical and thermal instability, and the potential for further propagation of lipid oxidation and eventual degradation. The aim of this review is to highlight the experimental conditions on sample preparation procedures, the LC-MS based analytical approaches for identification and quantification of oxygenated lipids, and their relation as potential biomarkers in diseases based on the most relevant articles published in the last five years. Regarding sample preparation, special attention has been given to antioxidants, internal standards, extraction and concentration methods, and derivatization approaches. Moreover, targeted, semi-targeted and non-targeted strategies have been discussed presenting examples. Finally, considerations on the structural identification, one of the main challenges, are presented.

Metabolites are the final products of the metabolism and are, therefore, directly related to phenotype. They constitute the metabolome of an organism. The wide diversity of the physicochemical properties of the metabolites in terms of molecular weight, concentration, polarity, volatility, solubility, pKa, and charge makes their analysis a remarkable challenge. With over 220,000 metabolites recorded in the HMDB database, there is no single analytical technique capable of analyzing all of them. Therefore, multiple analytical platforms are required to obtain a comprehensive picture of the metabolome. Among these platforms, mass spectrometry (MS)-based analytical techniques are among the most widely used. Capillary electrophoresis (CE) coupled to MS has been employed to analyze polar/ionic metabolites. Although this technique is not widely used, it has demonstrated unique capabilities for the detection of polar and ionic metabolites that are an essential part of the metabolome and are not usually detected by other techniques. This review highlights the role of CE-MS in untargeted metabolomics, particularly in comparison to the hydrophilic interaction chromatography (HILIC) separation mode. Additionally, we discuss the metabolomics workflow in CE-MS for untargeted metabolomics, including sample treatment and analysis, data treatment, and metabolite annotation. We notably present the annotation tools developed explicitly for CE-MS, as well as some computational alternatives, in-house libraries of relative migration times, effective mobility, MS/MS fragmentation, in-source fragmentation, and the CEU Mass Mediator online tool. Finally, we mention future perspectives of this technique, such as single cell-CE and ion mobility (IM)-MS. Overall, this review shows the important role of CE-MS in the studies of untargeted analysis published in the last five years to approach human diseases.

En la presente tesis se ha perseguido el desarrollo de nuevas metodologías o mejora de los métodos ya existentes para el análisis de distintas matrices biológicas (plasma, bilis y tejido pulmonar) que permitan obtener métodos analíticos optimizados, a través de las plataformas de electroforesis capilar (CE), cromatografía de líquidos (LC) y cromatografía de gases (GC) acopladas todas ellas a la espectrometría de masas (MS). Esta metodología se ha aplicado a diferentes estudios de cáncer (NET, colangiocarcinoma y NSCLC) abarcando una gran variedad de metabolitos que nos informan del estado alterado en esta enfermedad y nos han permitido establecer y validar, en algunas ocasiones, un potencial panel biomarcador. Además, se recoge el trabajo realizado durante estos años de investigación para el desarrollo e implementación de un método CE−MS para compuestos aniónicos en matrices biológicas. En él se plantea el uso de un capilar poco conocido con el fin de ampliar las posibilidades de esta técnica y se compara con otros capilares más comunes, empleando el método optimizado en un estudio de cáncer de pulmón.