title: Enhanced recovery of spermatozoa and comprehensive lysis of epithelial cells from sexual assault samples having a low cell counts or aged up to one year.
abstract: Differential extraction (DE) is the most common method for processing sexual assault samples, allowing for the simultaneous recovery of sperm and epithelial cells from the swab with the separation of sperm cells from epithelial cell DNA by exploiting the differences in the cell membrane susceptibility to detergents. However, sperm cell recovery when using DE is generally 40-50% [1], which can reduce the probability of obtaining a STR profile of the semen contributor, especially if the sample is aged or has a low number of sperm cells. Here, we present a novel buffer, containing SDS and ProK that, when used as an initial incubation buffer, enhances sperm cell recovery to as high as 90%, representing a 200-300% increase over conventional DE buffer. Adjusting the incubation time and temperature provided high, reproducible sperm cell yields. Sample vortexing and replacement of SDS with sodium octyl sulfate (SOS), another sulfate-based anionic detergent, did not provide any further enhancement of the sperm cell recoveries. Furthermore, the one-step buffer provided up to a 300% increase in recovery over the conventional DE buffer when used on samples aged up to one year. STR analysis of samples containing 500 or more sperm cells treated with this buffer showed comparable results (i.e., full STR profiles; 16 of 16 loci) to those obtained using a conventional DE buffer. Finally, when the sample contained only 400 sperm cells (recovered in 100μL volume, then extracted), substantially more STR loci (14 of 16) were generated using the novel buffer in comparison to the conventional DE buffer (4 of 16 loci). This work demonstrates that this buffer may be useful as an alternative for the initial sample incubation step in differential extraction, particularly for aged or samples known to have a low number of sperm cells.
authors: Department of Chemistry, University of Virginia, 409 McCormick Road, Charlottesville, VA 22904, United States; Center for Microsystems for the Life Sciences, University of Virginia, Charlottesville, VA 22904, United States.
authors: Jenny A
authors: JA
authors: Lounsbury
authors: Shanti M
authors: SM
authors: Nambiar
authors: Anne
authors: A
authors: Karlsson
authors: Helina
authors: H
authors: Cunniffe
authors: Jessica V
authors: JV
authors: Norris
authors: Jerome P
authors: JP
authors: Ferrance
authors: James P
authors: JP
authors: Landers
mesh_terms: D016922:Cellular Senescence; D004847:Epithelial Cells / Q000166:cytology*; D005554:Forensic Medicine; D006801:Humans; D008297:Male; D012742:Sex Offenses; D013094:Spermatozoa
keywords: Cell elution; Differential extraction; Forensic DNA analysis; Preferential lysis; Sexual assault samples