Analysis of Cellular and Extracellular DNA in Fingerprints.

摘要

It has been previously shown that DNA can be recovered from latent fingerprints left on various surfaces (R. A. H. van Oorschot and M. K. Jones, Nature 387, 767 (1997)). However, the source of the DNA, extracellular versus cellular origin, is difficult to determine. If the DNA is cellular, it is believed to belong to skin cells while extracellular DNA is believed to originate from body fluids such as sweat (D. J. Daly et. al, Forensic Sci. Int. Genet. 6, 41-46 (2012); V. V. Vlassov et. al, BioEssays 29, 654-667 (2007)). The origin of the DNA in fingerprints has implications for processing and interpretation of forensic evidence. The determination of the origin of DNA in fingerprints is further complicated by the fact that the DNA in fingerprints tends to be at a very low quantity (R. A. H. van Oorschot and M. K. Jones, Nature 387, 767 (1997)). This study examined fingerprints from five volunteers left on sterilized glass slides and plastic pens. Three fingerprints were left on each glass slide (thumb, index, and middle fingers) while the pens were held as if one was writing with them. The DNA was collected from the objects using the wet swabbing technique (TE buffer). Following collection, the cellular and extracellular components of each sample were separated using centrifugation and an acoustofluidics system. Centrifugation is still the primary separation technique utilized in forensics laboratories, while acoustic focusing uses sound waves to focus large particles (cells) into low pressure nodes, separating them from the rest of the sample matrix. After separation, all samples were quantified using real-time quantitative PCR (qPCR). The overall trend is that there is more DNA in the extracellular fractions than cellular fractions for both centrifugation and acoustofluidic processing. Additionally, more DNA was generally collected from the pen samples than the samples left on glass slides.