Method for Differential Extraction of Sperm in Mixture – IP 1404

Traditionally, cotton swabs have been used for collection ofbiological samples such as body fluids, touch samples, or other traceevidences. Despite being a common tool for sample collection, sample extractionfrom these swabs can be challenging due to strong adherence of the sample tothe matrix. Often the bulk of a collected biological sample remains entrappedin the cotton fibers even after elution, resulting in a loss of preciousevidence. For sexual assault casework in which there is a mixture of bodyfluids present, there are two challenges. First, the evidence is oftenoverwhelmed with the victim’s vaginal epithelial cells and secondly the poorrecovery from the swab can often make it difficult to recover the suspect maleDNA profile. Current separation extraction methods are difficult and timeconsuming, involve multiple wash steps, and produce insufficient sperm DNA recovery.Although there have been several efforts to improve either the recovery or theextraction of DNA from swabs taken following a sexual assault, the ability toachieve both would be desirable, especially for situations in which sample islimited. FIU inventors have developed a two-step protocol usingpressure cycling technology (PCT) and alkaline lysis for differentialextraction of mixture of sperm and female epithelial cells. Pressure treatment of the mixture in thepresence of alkaline conditions results in a near complete recovery of femaleepithelial DNA. Following this pressure treatment, exposing the composition toalkaline conditions at higher temperatures results in selective recovery ofsperm DNA with minimal contamination from female epithelial cells. Anne Laure Schmitt Olivier aschmitt@fiu.edu 305-348-5948