Magnetic bead-based separation of sperm from buccal epithelial cells using a monoclonal antibody against MOSPD3
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Forensic DNA analysis of sexual assault evidence requires unambiguous differentiation of DNA profiles in mixed samples. To investigate the feasibility of magnetic bead-based separation of sperm from cell mixtures using a monoclonal antibody against MOSPD3 (motile sperm domain-containing protein 3), 30 cell samples were prepared by mixing 104 female buccal epithelial cells with sperm cells of varying densities (103, 104, or 105 cells/mL). Western blot and immunofluorescence assays showed that MOSPD3 was detectable on the membrane of sperm cells, but not in buccal epithelial cells. After biotinylated MOSPD3 antibody was incubated successively with the prepared cell mixtures and avidin-coated magnetic beads, microscopic observation revealed that each sperm cell was bound by two or more magnetic beads, in the head, neck, mid-piece, or flagellum. A full single-source short tandem repeat profile could be obtained in 80 % of mixed samples containing 103 sperm cells/mL and in all samples containing ≥104 sperm cells/mL. For dried vaginal swab specimens, the rate of successful detection was 100 % in both flocked and cotton swabs preserved for 1 day, 87.5 % in flocked swabs and 40 % in cotton swabs preserved for 3 days, and 40 % in flocked swabs and 16.67 % in cotton swabs preserved for 10 days. Our findings suggest that immunomagnetic bead-based separation is potentially a promising alternative to conventional methods for isolating sperm cells from mixed forensic samples.
KeywordsMOSPD3 Immunomagnetic beads Sperm Short tandem repeat profile Forensic DNA analysis
This work was supported by a grant (No. 2011ZDYJCQSJ006) from the Ministry of Public Security of China. We thank Professor Anne Raffauf for her kind help.
Conflict of interest
The authors declare that they have no conflict of interest.
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