Department for Forensic Sciences, University of Split, 21 000 Split, Croatia.
Department of Integrative Physiology, School of Medicine, University of Split, 21 000 Split, Croatia.
Genes (Basel). 2024 Jul 6;15(7):888. doi: 10.3390/genes15070888.
The aim of this study was to investigate the effect of sunlight on the degradation of DNA samples taken from blood stains from different types of surfaces. A blood sample obtained from a single male donor was placed on seven different surfaces (galvanized sheet, iron rod, newspaper, white printer paper, glass, soil, and ceramic panel). Samples were kept, during a 4-week summer period, in a room, but next to an open window. Every 7 days, 1 mm of blood sample was collected from each substrate and stored in labeled tube for later analysis. DNA was extracted with the Chelex method, amplified using AmpFISTR Minifiler Plus Amplification Kit, and quantified using a Quantifiler Human DNA Quantification kit. After 7 days of sun exposure, the highest DNA concentration was determined to be from the sample from a galvanized sheet stain, followed by, in order of decreasing concentration, the ceramic panel, glass, newspaper, iron rod, and white printer paper surface. As expected, the DNA concentration from all samples decreased as the sunlight exposure time progressed. The results obtained after the amplification in the MiniFiler system were in correlation with the DNA concentrations measured by the qPCR method for all samples, except for the glass, soil, and white printer paper samples. The obtained data show that DNA degradation is correlated to the length of sunlight exposure and to the type of surface the samples are collected from. A negative qPCR result does not mean negative PCR amplification in the STR system; therefore, both methods should be applied when analyzing forensic samples collected from trace evidence.
本研究旨在探讨阳光对取自不同表面血斑的 DNA 样本降解的影响。从一名男性供体获得的血样被放置在七种不同的表面上（镀锌板、铁杆、报纸、白色打印机纸、玻璃、土壤和陶瓷板）。在一个夏季的 4 周内，将样本放置在一个房间内，但靠近敞开的窗户。每 7 天，从每个基质中收集 1 毫米的血样并储存在标记的管中以备后用。使用 Chelex 法提取 DNA，使用 AmpFISTR Minifiler Plus 扩增试剂盒进行扩增，并使用 Quantifiler 人类 DNA 定量试剂盒进行定量。经过 7 天的阳光暴露，从镀锌板污渍样本中确定了最高的 DNA 浓度，其次是陶瓷板、玻璃、报纸、铁杆和白色打印机纸表面，浓度依次降低。正如预期的那样，随着阳光暴露时间的延长，所有样本中的 DNA 浓度都降低了。在 MiniFiler 系统中扩增后获得的结果与所有样本的 qPCR 方法测量的 DNA 浓度相关，除了玻璃、土壤和白色打印机纸样本。所得数据表明，DNA 降解与阳光暴露时间的长短以及收集样本的表面类型有关。qPCR 结果为阴性并不意味着 STR 系统中的 PCR 扩增为阴性；因此，在分析从痕迹证据中收集的法医样本时，应同时应用这两种方法。
