Applicability of Nanotrap Sg as a semen detection kit before male-specific DNA profiling in sexual assaults

Abstract

A commercially available semen detection kit, Nanotrap Sg, which employs a one-step detection test based on immunochromatographic assay for the semenogelin protein, was evaluated for profiling male-specific DNA in sexual assault casework samples. While semen diluted with phosphate-buffered saline held and kept at 4 degrees C for 1 week showed a relatively strong signal intensity with Nanotrap Sg, the signal intensity was decreased by dilution after storage at 4 degrees C or freezing and thawing repeated more than three times. The reproducibility of Nanotrap Sg was tested on a total of 174 sexual assault casework samples from three forensic laboratories using intra- and interassay and no variation was observed in the semenogelin (Sg) signal. The positive signal ratio was 12.6% higher for prostate-specific antigen immunochromatographic membrane tests than Nanotrap Sg. Although spermatozoa were not confirmed in 61 (35%) out of 174 samples, Sg-positive signals could be detected from 41 (67%) of the 61 samples. Female genetic profiles could be observed in 95% of the samples, which tested negative for Sg on the Nanotrap Sg test, but no male genetic profiles could be observed. These results suggest that Nanotrap Sg can positively identify samples containing male DNA even in the absence of detectable intact spermatozoa. Further, Sg-positive signals identified samples for which male-specific DNA profiling could be performed, even if no sperm could be detected from the sample. The potential of Nanotrap Sg for identifying forensic samples with male-specific DNA was clearly demonstrated.

Identification of human semenogelin in membrane strip test as an alternative method for the detection of semen

“…The sensitivity of the ABAcard p30 Test was tested slightly better in this study than the value claimed by the manufacturer and was comparable to the reported sensitivity of two other PSA detection kits, Seratec PSA Semiquant and PSAcheck-1 [7]. The sensitivity of the RSID-Semen Test was equivalent to that of another recently commercialized Sg detection kit called Nanotrap Sg [20]. With both tests capable of detecting the human semen and the seminal fluid standard at 50,000-fold dilution, they are considered offering highly sensitive tests for the detection of semen.…”

Investigative strategy for the forensic detection of sperm traces

“…The minimal concentration here was 1.77 ng PSA/ml. The semelogelin test, which is said to have a higher sensitivity than the PSA test, was recently introduced as a further preliminary test for sperm [16,17].…”

Immunohistochemical staining of human sperm cells in smears from sexual assault cases

“…The slides are then normally kernechtrot picroindigocarmine (KPIC) stained and examined for sperm cells using brightfield microscopy. The microscopy provides a rapid answer to whether or not the sample is likely to contain enough DNA for profiling and is one of the traditionally used methods together with prostate specific antigen, seminal acid phosphatase and semenogelin measurements for indication of semen or seminal fluids in the sample [1][2][3][4][5].…”