Tese de mestrado, Bioquímica (Bioquímica) Universidade de Lisboa, Faculdade de Ciências, 2021Throughout the years, fingerprints have been used in criminal investigations to place a suspect at a crime scene. However, this method depends on the integrity of the fingermark, on the method used for its recovery and if the respective fingerprint is listed or not on the National/International Fingerprint Database. The ridge pattern does not use all available information, most notably, the chemical signature that is left behind. So, it could be extremely beneficial to invest in techniques that can retrieve basic donor information in fingerprints’ chemical composition. Until now, human fingerprints have been mainly analysed by low resolution mass spectrometry methods. There is one particular area of mass spectrometry that has led the study of fingerprint’s chemical composition and it is Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI MS). With this technique, not only a fingerprint’s image is obtained, which may be used in a biometric identification, but it’s also possible to profile the fingerprint’s chemical composition. However, this type of approach does not allow a bulk analysis of its chemical composition. With that in mind, this work coupled Electrospray Ionization (ESI) with a high resolution mass spectrometry method such as FT-ICR MS, to reveal the chemical composition of human fingerprints. The compositional space of 10 fingerprints was analysed combining accurate mass measurements, database search and molecular formula determination, which was explored trough Principal Component Analysis (PCA), Kruskal-Wallis tests and other tools. From the thirty eight compounds commonly found in all fingerprints that were analysed, twenty (mainly lipids), such as palmitic acid, oleic acid, stearic acid and linoleic acid, were present with similar intensities. This was the first step towards the definition of a chemical background for the composition of human fingerprints in relation to which everything else can be found. Understanding the source of these compounds will be important for the interpretation of their possible roles on fingertips and potential uses in forensic and other contexts. Despite the main focus being endogenous compounds, we also found several exogenous com-pounds, for example, pantothenol which is present in personal care products, mainly shampoos. It was possible to verify that in fact this compound was part of the composition of the shampoo used by the volunteer in question. Therefore, the use of ESI together with FT-ICR MS has proven to be a promising analytical method for studying the chemical signature of fingerprints due to its unmatched sensitivity for detecting any type of molecules, extreme sensitivity, requiring only minute amounts of sample and the fact that it is an high-throughput method. Thus, it can be used not only from a forensic point of view, but also in other contexts, namely, clinical
