Identification of Drug-related Compounds in Body Fluid Stains on Forensically Relevant Surfaces at Atmospheric Pressure using DESI Mass Spectrometry

法医调查经常涉及对犯罪过程中溢出的体液进行分析，导致在地毯、墙壁、衣服、床单和皮肤等广泛的表面上沉积。例如，血迹检测药物和与药物有关的代谢物或其他生物标记物的存在可能是一项非常复杂的程序，由于提取过程中物质的损失以及缺乏绝对灵敏度，这类分析的成功率可能会受到严重限制。此外，这些测试的固有破坏性--在进行任何提取之前需要将样品从散装物品中取出--是一个主要问题，因为分析总是在远离现场的实验室进行。远程分析的必要性也确实增加了调查过程的潜在关键时间，并带来了样品在运输和随后储存过程中退化和污染的固有风险。也许最重要的是：如果从物品中取出合适的样本是不可行的，调查人员就无法获得潜在的有用信息。因此，法医从业者对可能至少克服其中一些重要限制的技术非常感兴趣。在这项建议中，我们打算进行一项可行性研究，以评估已建立的质谱学技术在此类法医调查中的新应用。质谱仪是一种非常强大和成熟的技术，能够以非常高的灵敏度和特异度检测微量物质。遗憾的是，它存在一些严重的缺陷，严重限制了它的适用性。这些缺陷主要涉及对被调查材料的采样，这些材料必须能够处于气相。对于固体衬底，这往往特别困难，需要物理移除和溶解感兴趣的材料，在超高真空室中用高能离子轰击样品，或在施加基质材料后用强激光照射样品。所有这些方法在法医分析领域都存在很大问题，因为在法医分析领域，受试者的完整性至关重要。因此，一种符合法医要求的挥发感兴趣物质的方法将具有巨大的潜力。新引入的DESI技术，即解吸电喷雾电离，具有尚未实现的潜力，可以成为一种成熟的常规表面分析工具，将质谱学的分析能力与便于法医分析的采样设施相结合。与大多数其他此类技术不同，它适用于广泛的环境条件，适用于各种样品，包括生物、制药、聚合物、金属和矿物材料的表面。此外，目前的技术能力使许多小型化成为可能，从而产生台式设备，甚至可能是便携式设备。拟议的工作重点是将该技术应用于与法医相关的对象和材料，更具体地说，是在犯罪现场发现的体液污渍中检测毒品和药物代谢物。将与药学院现有的两种已有的能够进行表面分析的质谱学技术-二次离子质谱仪(SIMS)和基质辅助激光解吸-电离(MALDI)-产生的质谱图进行直接比较，这两种技术都使用不同的挥发方法。应当强调的是，虽然这项建议集中于一种非常具体的样本类型，但该技术显然有潜力应用于法医科学领域更广泛的样本。

Forensic investigations frequently involve the analysis of body fluids spilled during the commissioning of a crime, leading to deposits on a wide range of surfaces such as carpets, walls, clothing, bedlinen and skin. Testing of, for example, bloodstains for the presence of drugs and drug-related metabolites or other biomarkers can be a highly complex procedure, and the success rate of such analyses can be severely limited due to loss of material during extraction, as well as a lack of absolute sensitivity. Moreover, the inherently destructive nature of these tests - specimens need to be removed from the bulk item before any extraction can be carried out - is a major issue, as is the fact that analysis is invariably carried out at a laboratory remote from the scene. The necessity for remote analysis does also add potentially crucial time to the investigative process, as well as carrying an inherent risk of sample degradation and contamination in transit and subsequent storage. Perhaps most importantly: if it is not feasible to remove a suitable sample from an item, potentially useful information will not be available to investigating officers. Therefore, forensic practitioners have considerable interest in technologies which could potentially overcome at least some of these important limitations.In this proposal we intend to undertake a feasibility study to assess a novel application of the established technique of mass spectrometry in such forensic investigations. Mass spectrometry is a very powerful and well-established technique able to detect minute amounts of materials with very high sensitivity and specificity. Unfortunately, it has some serious drawbacks which severely restrict its applicability. These drawbacks chiefly concern the sampling of the materials under investigation, which have to be capable of being in the gas phase. This tends to be especially difficult from solid substrates, necessitating physical removal and dissolution of the material of interest, bombardment of the sample with highly energetic ions in an ultrahigh vacuum chamber, or illumination of the sample with an intense laser beam after application of a matrix material. All these methods are highly problematic in the field of forensic analysis, where integrity of the subject is of utmost importance. A methodology to volatilise materials of interest for mass spectrometric analysis which is compatible with forensic requirements would thus have great potential.The newly-introduced technique of DESI, short for desorption electrospray ionisation, has such potential, as yet to be realised, to become a fully-fledged routine surface analytical tool, marrying the analytical capabilities of mass spectrometry with a sampling facility convenient for forensic analyses. As opposed to most other such techniques, it is applicable under a wide range of environmental conditions and suitable for a wide array of samples including surfaces of biological, pharmaceutical, polymer, metal and mineral materials. Moreover, current technical capabilities are such that a great deal of miniaturisation is possible, leading to a desktop-sized or potentially even a portable device.The proposed work focuses on the application of the technique to forensically relevant subjects and materials, more specifically the detection of drugs and drug metabolites in body fluid stains found at scenes of crime. Direct comparisons will be made with mass spectra generated using two established mass spectrometry techniques capable of surface analysis available in the School of Pharmacy, secondary ion mass spectrometry (SIMS) and matrix assisted laser desorption-ionisation (MALDI), which both employ different methods of volatilisation. It should be stressed that whereas this proposal concentrates on a very specific sample type, the technique has the clear potential for application to a much wider range of samples in the forensic science field.