Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P. R. China.
Institute of Forensic Science, Ministry of Public Security, Beijing 10038, P. R. China.
ACS Appl Mater Interfaces. 2021 Apr 7;13(13):15621-15632. doi: 10.1021/acsami.1c00710. Epub 2021 Mar 29.
Latent blood fingerprints (LBFPs) can provide critical information of foul play and help identify the suspects at violent crime scenes. The current methods for LBFP visualization are still not satisfactory because of the low sensitivity or complicated protocol. This study demonstrates a simple and effective LBFP visualization strategy by integrating a new amphiphilic fluorescent amino-functionalized conjugated polymer with the cotton-pad developing protocol. LBFPs on various substrates are visualized by simply covering them with the polymer solution-soaked cotton pads. The images display clear fingerprint patterns, ridge details, and sweat pores, even on very challenging substrates such as painted wood and multicolored can. The gray value analysis confirms semiquantitatively the enhancement of the contrast between ridges and furrows. Even LBFPs with various contaminations or aged for more than 600 days are effectively developed and visualized. The developed fingerprint images show superior stability over long storage time and against solvent washing. Moreover, the polymer causes no degradation of DNAs in the blood, suggesting the possibility of further DNA profiling and identification after development. The mechanistic investigation suggests that the formation of positive or inverted images can be attributed to the synergistic effects from the affinity between polymer and blood, and the affinity betwen polymer and substrate, as well as the slight quenching of polymer fluorescence by blood. Furthermore, the covalent bonding between the protonated primary amino group and proteins in blood endows the stability of the developed fingerprints. The result rationalizes the molecular design of the fluorescent polymer and sheds new light on the future strategies to effective LBFP visualization in practical applications.
潜伏血指纹 (LBFPs) 可以提供有关犯罪行为的关键信息，并有助于在暴力犯罪现场识别嫌疑人。目前的 LBFPs 可视化方法由于灵敏度低或协议复杂，仍然不能令人满意。本研究通过整合一种新的两亲性荧光氨基功能化共轭聚合物与棉花垫开发方案，展示了一种简单而有效的 LBFPs 可视化策略。只需用聚合物溶液浸泡的棉花垫覆盖各种基质上的 LBFPs，即可可视化 LBFPs。图像显示出清晰的指纹图案、脊线细节和汗孔，即使在非常具有挑战性的基质上，如涂漆木材和彩色罐头也能如此。灰度值分析半定量地证实了脊线和凹槽之间对比度的增强。即使是带有各种污染或老化超过 600 天的 LBFPs，也可以有效地开发和可视化。开发后的指纹图像在长时间储存和耐溶剂清洗方面表现出优异的稳定性。此外，聚合物不会导致血液中的 DNA 降解，这表明在开发后有可能进一步进行 DNA 分析和鉴定。机理研究表明，正像或倒像的形成归因于聚合物与血液之间的亲和力、聚合物与基质之间的亲和力以及血液对聚合物荧光的轻微猝灭之间的协同作用。此外，血液中质子化的伯氨基与蛋白质之间的共价键赋予了开发的指纹的稳定性。该结果合理化了荧光聚合物的分子设计，并为未来在实际应用中实现有效的 LBFPs 可视化策略提供了新的思路。
