Leverhulme Research Center for Forensic Science, University of Dundee, Smalls Wynd, Dundee DD1 4HN, UK.
Leverhulme Research Center for Forensic Science, University of Dundee, Smalls Wynd, Dundee DD1 4HN, UK.
Forensic Sci Int Genet. 2024 May;70:103011. doi: 10.1016/j.fsigen.2024.103011. Epub 2024 Jan 29.
It is imperative for proper evidence triage that forensic biologists understand what kind of results to expect from certain evidence types submitted for DNA analysis. The persistence of trace DNA has been insufficiently investigated and there is little data available pertaining to the persistence of DNA in different environmental conditions and on different materials. The goal of this study is to increase the available data on this topic which would, in turn, help forensic biologists manage expectations when submitting specific evidence types for DNA testing. The work presented herein is a large-scale persistence project aimed to identify trends in the persistence of trace DNA and indicate how different environmental storage conditions and target surface characteristics influence the persistence of cellular and cell free DNA (cfDNA) over time. To eliminate variation within the experiment we used a proxy DNA deposit consisting of a synthetic fingerprint solution, cellular DNA, and/or cfDNA. Samples were collected and analysed from 7 metals over the course of 1 year (27 time points) under 3 different environmental storage conditions. The results of this experiment show that metal type greatly influences DNA persistence. For instance, copper exhibited an expected poor DNA persistence (up to 4 h) which a purification step did not help increase the DNA yield. Alternatively, DNA can persist for up to a year on lead at levels potentially high enough to allow for forensic DNA testing. Additionally, this study showed that the sample storage environment had no impact on DNA persistence in most cases. When considering DNA type, cfDNA was shown to persist for longer than cellular DNA and persistence as a whole appears to be better when DNA is deposited as mixtures over when deposited alone. Unsurprisingly, it can be expected that DNA recovery rates from trace deposits will decrease over time. However, DNA decay is highly dependent on the metal surface and extremely variable at short time points but slightly less variable as time since deposition increases. This data is intended to add to our understanding of DNA persistence and the factors which affect it.
为了正确进行证据筛选，法医学家必须了解从提交进行 DNA 分析的特定证据类型中应期望获得哪种结果。痕量 DNA 的持久性尚未得到充分研究，并且有关不同环境条件和不同材料上 DNA 持久性的数据很少。本研究的目的是增加有关该主题的可用数据，这反过来将有助于法医学家在提交特定证据类型进行 DNA 测试时管理预期。本文介绍的工作是一项大规模的持久性研究项目，旨在确定痕量 DNA 持久性的趋势，并指出不同的环境存储条件和目标表面特性如何随时间推移影响细胞和无细胞 DNA（cfDNA）的持久性。为了消除实验中的差异，我们使用了一种由合成指纹溶液、细胞 DNA 和/或 cfDNA 组成的代理 DNA 沉积物。从 7 种金属中收集了样本，并在 3 种不同的环境存储条件下在 1 年内（27 个时间点）进行了分析。该实验的结果表明，金属类型对 DNA 的持久性有很大影响。例如，铜显示出预期的较差的 DNA 持久性（长达 4 小时），而纯化步骤并不能帮助提高 DNA 产量。另一方面，在铅上，DNA 可以持续存在长达一年，其水平足以进行法医 DNA 测试。此外，本研究表明，在大多数情况下，样本存储环境对 DNA 持久性没有影响。就 DNA 类型而言，cfDNA 比细胞 DNA 持续时间更长，并且当 DNA 作为混合物而不是单独沉积时，整体持久性似乎更好。毫不奇怪，可以预期随着时间的流逝，从痕量沉积物中回收的 DNA 率将会降低。但是，DNA 衰减高度依赖于金属表面，在短时间点变化极大，但随着沉积时间的增加，变化稍小。该数据旨在增加我们对 DNA 持久性及其影响因素的理解。
