Aplicações de espectrometria de massas ambiente em metabolômica clínica

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Universidade Federal de Goiás


Most clinical biofluids studies are based on plasma/serum and urine, which are more free and representative models of general metabolism. Each of these fluids has a unique matrix, comprising different levels of proteins and metabolites. Therefore, it is important to optimize sample preparation and analytical methods to achieve comprehensive coverage of the analytes present in these samples. In this context, Ambient Mass Spectrometry (AMS) arises, which is a family of desorption and ionization techniques that have revolutionized the way of obtaining ions in mass spectrometry. These techniques share the ability to generate ions in the gas phase directly from untreated samples, reducing or virtually eliminating analyte extraction and prior separation. Substrate Electrospray Ionization are ionization techniques in AMS, which comprise, for example, Paper spray ionization (PSI) and Probe electrospray ionization (PESI). In this study, two analytical approaches are proposed in clinical metabolomics using PSI and, also, the development of a new Substrate Electrospray Ionization. The first approach is the use of a paper coated by a molecularly printed polymer (MIP) as a substrate for PSI in metabolite analysis: dopamine, sarcosine and butyric acid in artificial urine. This new substrate was highly selective for the desired targets, in addition to minimizing the effects of common ion suppression on PSI. In addition, calibration curves with R2> 0.99 and limits of detection (LOD) and quantification (LOQ) in the ppb range were obtained. In addition, success was obtained when using this technique for the analysis of dopamine in a real sample. In the second approach, PSI was combined with a chemometric approach called Interval-successive projections algorithm linear discriminant analysis (iSPA-LDA) to detect lipid biomarkers of cervical cancer using unprepared blood plasma lipids. A total of 86 blood plasma samples from different women were collected, including 37 cancer controls and 49 healthy controls, where 8 lipids were found as possible biomarkers with an overall precision of 77%. The results show the potential of PSI associated with multivariate analysis as a complementary tool for the screening or diagnosis of cervical. It is the application of PSI in plasma samples in a non-targeted lipidic approach, with the objective of discovering biomarkers of cervical cancer. The final approach was to use graphite as a substrate for ESI. The effect of voltage, probe angle and sample volume were evaluated. The ionization capacity of several analytes, including a protein, has also been evaluated, and creatinine quantification tests have been performed on real urine samples. The ESI graphite technique was optimized and obtained excellent ionization of the analytes, not presenting ionic suppression. It was possible to determine the amount of creatinine present in the samples tested and all were within the established limits. In addition, the technique was employed in mouse brain analysis and through these analyzes combined with Principal Component Analysis (PCA) it was possible to differentiate different regions of the brain and separate the samples in male and female. With this, the graphite ESI technique proved very efficient to be used in metabolomic approaches.



MENDES, T. P. P. Aplicações de espectrometria de massas ambiente em metabolômica clínica. 2019. 126 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2019.