Quantificação de DNA de impressões digitais latentes em diferentes superfícies

Abstract

In forensic sciences, the study of DNA from biological traces found at crime scenes is crucial in the elucidation of criminal cases and human identification. The most diverse types of biological traces can be found in a crime scene and, among the best known, are fingerprints. Every day our cells detach from the body and remain on surfaces where we have contact and, depending on the type of surface we touch and individual factors, we leave more or less DNA, that is, the amount of DNA left on different substrates varies. It is important that the genetic material deposited in forensic samples is in good conditions of integrity that allows its detection and subsequent study. In addition, there needs to be a sufficient amount of this material to be able to quantify and use it in identifying people and obtaining answers about a crime. An important tool used in many researches in the most diverse areas is the Real Time PCR (qPCR) technique. This is a highly sensitive and fast technique in which it is possible to detect minimal amounts of the material to be amplified, in addition to being able to monitor such amplification, without the need for postprocessing of the amplified material, as is done in conventional PCR. In this study, we sought to quantify, through Real Time PCR, the DNA of latent fingerprints deposited on different substrates and to evaluate in which of these a larger or smaller volume of DNA was left. Plastic, glass and metal surfaces were tested. Fingerprints deposited by donors on different substrates were demarcated and collected with moistened swabs and, subsequently, DNA was extracted from the collected samples. After extraction and purification, the DNA samples were amplified by qPCR and, from this process, the amount of amplified DNA was analyzed, evaluating the values presented by the software and comparing the amount of DNA on each type of surface. Descriptive statistical analysis was performed to estimate the mean, variance and standard deviation of the data obtained. To compare the average concentrations of DNA deposited on different substrates, Analysis of Variance (ANOVA) was performed. This work demonstrated that, among the surfaces studied (glass, plastic and metal), the one with the highest amount of DNA left by fingerprints was metal surfaces, with an average of 0.9453 ng/µl, followed by plastic, with average of 0.1362 ng/µl and glass, with an average of 0.0545 ng/µl. There was no significant difference between the average amounts of DNA recovered from the surfaces studied in this work. In Forensic Genetics, it is relevant to determine the average amount of DNA deposited in each type of substrate because, based on these data, it is possible to facilitate investigative work and carry out the identification of individuals. Furthermore, the described technique proves to be essential for this type of study and allows important steps in the forensic area to be taken safely, quickly and practically.