Development of a Systematic Method for Identifying Saliva, Sweat and Urine by Enzyme-linked Immunosorbent Assay with Statherin, Dermcidin and Tamm-Horsfall Protein Markers

Detection of prostate-specific antigen in semen using DNA aptamers: an application of nucleic acid aptamers in forensic body fluid identification

In forensics, body fluid identification plays an important role because it aids in reconstructing a crime scene. Therefore, it is essential to develop simple and reliable techniques for body fluid identification. Nucleic acid aptamers are useful tools in analytical chemistry that can be used to improve conventional forensic analytical techniques. They have numerous advantages over antibodies including their low cost, long shelf life, and applicability for chemical modification and PCR amplification. A DNA aptamer against a human prostate-specific antigen (PSA), which is a well-known protein marker for semen identification in forensics, has been reported previously. In this study, as a proof-of-concept for nucleic acid aptamer-based identification of body fluids, we developed a technique of aptamer-based PSA assays for semen identification that employed enzyme-linked oligonucleotide assay (ELONA) and real-time PCR. We evaluated their sensitivity and specificity for semen compared with those for blood, saliva, urine, sweat, and vaginal secretion. The assays have equivalent procedures compared to enzyme-linked immunosorbent assay; their results were consistent with those produced by the conventional immunochromatographic assay. The minimum volume of semen required for detection was 62.5 nL in ELONA and 5 nL in real-time PCR, making this assay applicable for semen detection in actual criminal investigation. Aptamers can be a cost-effective and versatile tool for forensic body fluid identification.

Evaluation of skin- or sweat-characteristic mRNAs for inferring the human origin of touched contact traces

The source of small amounts of touch DNA, which is transferred from the skin to an object when it is handled or touched, could be an issue in the forensic analysis of criminal cases. Here, we performed an extended evaluation of skin- or sweat-characteristic mRNAs to investigate their usability to infer whether an object has been handled or touched by someone. First, we compared the expression levels of candidate genes between skin swabs and other body fluids by quantitative RT-PCR analysis. Among the analyzed genes, corneodesmosin (CDSN), late cornified envelope 1C (LCE1C), filaggrin (FLG), desmocollin 1, and dermcidin were selected for further analysis on the basis of their specificities and sensitivities. Then, we tried to detect these genes from mock casework samples. As a result, CDSN, LCE1C, and FLG could be good markers because of their detectability. Finally, we determined the correlation between the expression of these genes and DNA yield of skin swabs to assess their adaptability as a screening test for touch DNA samples. However, the detectability of these genes was not correlated with the DNA yield of skin swab samples. In conclusion, gene expression analysis of the skin- or sweat-characteristic mRNAs CDSN, LCE1C, and FLG could be useful for inferring the skin origin of touched contact traces, but the use of the expression levels of these mRNAs for the prediction of DNA yield is problematic. To develop a screening test for touch DNA samples, other markers that have a well-correlated sensitivity with DNA analysis should be investigated.