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Development of an Immuno-Magnetic Procedure for the Separation of Spermatozoa from Vaginal Epithelial Cells

NCJ Number
Date Published
May 2015
39 pages
In an effort to develop a more efficient, automatable method for separating spermatozoa from vaginal epithelial cells in processing sexual assault evidence, this project's goal was to use immuno-magnetic bead "capture and release" chemistry in binding spermatozoa and sperm heads while all other cell types are removed.

This was an effort to improve on the manual differential lysis extraction first described over 20 years ago, which is currently the most common method for separating sperm cells from vaginal epithelial cells. Overall, this project never matured to the stage where real cell separation for sperm/vaginal cell was attempted. Several promising sperm membrane-specific antigens were identified, based on published research and the human gene compendium. Target proteins for the antibodies tested included ADAM2, AKAP3, MFGE8, MOSPD3, Ropn11, SPAM1, and UBAP2L. One type of capture chemistry tested in this study was magnetic beads covered with Protein G, which exhibits a high affinity for immunoglobulin (IgG) and will bind this antibody domain. The other bead type was covered with streptavidin, thus reacting with any biotinylated antibodies. Two different biotin conjugates (DSB-X Biotihn and EZ-link sulfo-NHS-LC-Biotin) were tested for this labeling step. Varying numbers of single source sperm cells and female vaginal epithelial cells were processed with different antibodies and both types of beads. In order to separately evaluate the captured cells bound to the beads and the remaining cells still in solution, both the "capture" fraction and the "supernatant" fraction were subjected to DNA extraction and quantitation with a real time PCR assay specific for a human DNA target and a male Y-chromosome sequence. Based on the results for single source samples, this project never matured to the stage where real cell separation for sperm/vaginal cell mixtures was attempted. 7 tables, 4 figures, and 56 references

Date Published: May 1, 2015