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.