Utilização do kit DNA IQ™ system na extração de dna por lise diferencial em amostras coletadas de vítimas de crime sexual

Abstract

Forensic samples from cases of sexual crime are often characterized by an unbalanced mixture between the victim's epithelial cells and sperm cells of the offender. DNA extraction by organic differential lysis is still the methodology routinely used to process the separation of male and female DNA in these samples, based on the resistance of the nuclear membrane of the sperm cells to certain reagents. However the technique is extremely time consuming and uses toxic organic solvents such as phenol and chloroform and modifications in this protocol has been a challenge for the forensic laboratories in the world. This study propose the use of DNA extraction kit DNA IQ™ System (Promega) with magnetic particles to eliminate some drawbacks of the standard technique. To perform a comparative analysis between the current use technique and the proposed, 50 samples of sexual crimes were submitted to the same analysis conditions by the two methodologies, resulting in 100 extraction products non-sperm fraction (NSF) and 100 sperm fraction (SF) results. Samples were quantified by real-time PCR using the Plexor HY® System kit (Promega) to evaluate the quantity and quality of amplified autosomal and Y chromosome DNA. 86% of the sperm fractions (SF) from the extraction using the DNA IQ™ System kit presented higher amount of amplified DNA autosomal compared to the standard differential extraction. With respect to Y chromosome DNA, 66% of the samples extracted using the commercial kit technique offered higher amounts of amplified DNA as compared to the standard technique. Statistical analyzes were performed using GraphPad Prism® v.6.0 software and the Wilcoxon test showed that the differences were considered statistically significant with p < 0.0001. The research demonstrated that the technique using the DNA IQ™ System kit is more efficient than the organic differential technique in all analyzed parameters, providing the elimination of toxic solvents, guaranteeing greater security for the forensic analyst, faster execution of the extraction and favorable quantity and quality of recovered DNA. Therefore, its implementation is indicated as an alternative method in forensic laboratories to analyze samples of sexual crime.