Violent contact between individuals during a crime can result in body fluids becoming trapped under the fingernails of the individuals involved. The traces under fingernails represent valuable forensic evidence because DNA profiling can indicate from whom the trace originated and proteomic methods can be used to determine the type of fluid in the trace, thus providing evidence as to the circumstances surrounding the crime. Here, we present an initial study of an analytical strategy that involves two complementary techniques, direct PCR DNA profiling and direct mass spectrometry-based protein biomarker detection, for the comprehensive examination of traces of biological fluids gathered from underneath fingernails. With regard to protein biomarker detection, direct MALDI-ToF MS/MS is very sensitive, allowing results to be obtained from biological material present on only a few fibres plucked from a microswab used to collect the traces. Human cornulin, a protein biomarker for vaginal fluid, could be detected up to 5 h after it had been deposited under fingernails whereas haemoglobin, a biomarker for blood, is somewhat more persistent under fingernails and could be detected up to 18 h post-deposition. Bottom-up tandem mass spectrometry techniques were used to provide a high level of confidence in assigning the identity of protein biomarkers. nLC-ESI-qToF MS/MS offered higher levels of confidence and the ability to detect traces that had been present under fingernails for longer periods of time, but this performance came with the cost of longer analysis time and a more laborious sampling approach.
Forensic science Haemoglobin Vaginal fluid MALDI-TOF MS
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The authors would like to acknowledge Flinders Analytical and the Proteomics Centre at Flinders University. We also thank the volunteers who provided human body fluid samples and kind thanks to Dr. Jennifer Templeton and Ms. Alice Stephenson (Forensic Science SA) for conducting the DNA-profiling experiments.
This project was supported by the Ross Vining Research Fund, which is administered by Forensic Science SA (South Australia).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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