Rapid Extraction of Sperm from Sexual Assault Kits

As submitted by the proposer: Analyzing sexual assault kits is a very costly, time-consuming, and tedious practice that requires trained personnel. Isolating sperm cells deposited by the perpetrator from epithelial cells inherent in/on the victim is easily the most complex step in the analytical process. The purpose of this project is to develop a new means for isolating spermatozoa from epithelial cells by exploiting the way in which these cells focus in an electric field and under applied pressure. This method, gradient elution isotachophoresis, is a proven technique for isolating charged, bulky molecules in crude and dirty matrices in a timeframe of only 5 minutes. Further, the method requires few consumables, uses simple instrumentation, and is highly reproducible. Finally, the instrumentation is amenable to multiplexing, for a potential throughput of 960 samples/hour after further modification. This project has direct relevance to addressing the current backlog of sexual assault kits by significantly reducing the time, cost, and difficulty required to process samples. By decreasing the time required for analysis, perpetrators can be apprehended and prosecuted earlier and innocent men can be exonerated faster. We will work with the Harris County Institute of Forensic Sciences to understand the problems associated with processing sexual assault kits, including features of stored spermatozoa, appropriate means of collecting the sample from the materials within the kit, and forensic analysis methods. Our 12-month project will begin by visualizing spermatozoa and epithelial cells to ascertain their characteristics in an electric field and under applied pressure. We will determine how fast spermatozoa and epithelial cells move in an electric field and the chemical conditions required to change their speeds, if necessary. A key challenge includes developing the chemical conditions required to fully separate the spermatozoa from any undesirable materials. We will optimize the extraction process and, finally, we will test the method and instrument using mock sexual assault samples. We will analyze collected spermatozoa with standard forensic analysis protocols and determine extraction efficiency and the purity of the extracts. We will also determine the time required for extracting clean, pure spermatozoa fractions. Note: This project contains a research and/or development component, as defined in applicable law. ca/ncf