Sperm fishing: antigen-antibody complexes for the capture and enrichment of spermatozoa in mixed cell substrates

Abstract

ABSTRACTIn many sexual assault cases, the most common evidence gathered comes in the form of intimate swabs. These swabs contain cells from both the female and male. In these cases the most common cell present is epithelial cells from the female with relatively few spermatozoa from the male. To produce an STR DNA profile suitable for an investigation, separation of the cell types is required to prevent a mixed profile that may complicate interpretation. While there are methods that can achieve this separation, they are labour intensive and have no guarantee of complete separation of the spermatozoa. Immunomagnetic bead separation techniques are being adapted from other scientific fields to be used in forensic biology to separate spermatozoa from mixed substrates. This study tested the binding of a Hyaluronidase PH-20 (SPAM1) antibody to spermatozoa in mixed cell samples that have been dried and stored for a short period of time. Fluorescently tagged antibodies were incubated with cellular mixtures and visualized using fluorescent microscopy. Successful binding of the antibodies to spermatozoa was observed in all samples. The SPAM1 antibody appears to be suitable for selection of spermatozoa and creates opportunities for linking with magnetic beads facilitate cell separation and DNA profiling.