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Rapid Extraction of Sperm From Sexual Assault Kits

NCJ Number
Date Published
January 2018
12 pages
The goal of this research project was to use an optimized electrolyte system and a gradient elution isotachophoresis (GEITP) protocol in assessing the feasibility of GEITP-based sperm cell extractions from a mixture of both sperm and epithelial cells from a victim in a sexual assault kit (SAK).

A successful GEITP protocol would be one in which only sperm cells are extracted from a mixture of both sperm and epithelial cells; i.e., no epithelial cells are present in the extract. The primary method used in the research was GEITP, which uses a combination of pressure-based flow and isotachophoresis to focus charged molecules or particles on the basis of electrophoretic mobility, or their mobility in an electric field. GEITP uses two aqueous buffers with different electrophoretic mobilities. The electrophoretically fast buffer is the leading electrolyte (LE); and the electrophoretically slow buffer into which the sample is slurried is the trailing electrolyte (TE). Researchers have performed GEITP extractions using pH 4.6 - pH 5.1 buffers; the LE is composed of acetic acid/NaOH, and the TE is acetic acid/pyridine. At these pH values, the data (qPCR) indicate very little overall cell extraction and subsequent DNA detection. The procedures followed are described in detail in this report. The report indicates that this project is still in the basic research phase of the testing of the methodology; however, the researchers express confidence that when the GEITP technique is optimized, it will lower the burden on crime lab resources by reducing personnel, time, and costs. Using inexpensive instrumentation and reagents, the researchers anticipate that the method will rapidly provide pure fractions of spermatozoa that is free from contamination by victim cellular material or DNA. 1 figure

Date Published: January 1, 2018