Determination of blood and saliva in mixture samples with miRNA

Sexual abuse and rape are among the crimes that are increasing day by day in our country. According to 2019 TUIK data, 13.1% of children brought to security units are victimized by sexual crimes. According to data published by the World Population Review website in 2020, 1071 people were raped in Türkiye that year. The provability of crimes is a very important factor for the perpetrator to be punished. The field of forensic sciences tries to serve justice by examining the evidence found at the crime scene. In cases where the possible body fluids of the perpetrator and the victim are mixed, it is very difficult to make an identification because there is no method for the separation of these mixed samples. In this study, we aimed to differentiate mixed body fluids (blood and saliva) by microRNA method. The samples collected from volunteers for this study were prepared as two-donor mixtures in four different groups in five different dilutions. A total of 36 mixtures were prepared from fluids collected from 4 female and 4 male individuals. The miR-451A biomarker was used to indicate the presence of blood and the miR-203A-3p marker was used to indicate the presence of saliva in the mixture samples. The samples were first centrifuged and then RNA isolation was performed using miRNeasy Mini Kit. The concentration and purity of the obtained RNAs were determined by spectrophotometer. Then cDNA (complementary DNA) was synthesized from RNAs with Taqman microRNA Reverse Transcription Kit.U6 gene region was preferred as the reference gene and analyzes were performed by RT-PCR. The presence of blood samples in the mixture was shown in all dilutions, the best level was seen in 1x1 ratio. When all groups were analyzed, it was seen that the mixtures with male donors were expressed at a higher rate than the other mixtures.