Automation of a Sperm DNA Capture Assay for Forensic Applications

As submitted by the proposer: The backlog of sexual assault samples awaiting processing in US crime labs is estimated to be nearly half a million. One cause attributable to the build-up of this backlog is due to the time and labor involved in the processing of the sample to separate the sperm cells of the assailant from the epithelial cells of the victim. A process known as differential extraction is used as an initial step for separating the sperm cells from other cells prior to isolating the DNA for identification of the assailant. Without this step, the DNA from the victim and assailant are mixed and uninterpretable. For lack of a better solution that would allow automation, differential extraction is by-and-large the sole method currently used throughout US crime labs. As the differential extraction process requires the cell material to be of very high quality, there is a finite window from which samples can be collected from the victims. Others have tried to develop better methods to increase speed and sensitivity, but all these approaches have a core requirement that the sperm and epithelial cells be intact, and none have been widely adopted by forensic labs. We have developed a new approach to the processing of these samples that does not require intact cells, as the separation we achieve is through the specific capture of sperm DNA using antibodies against unique proteins only found associated with the sperm DNA. These proteins, called protamines, are absolutely unique to mature sperm. We feel there is also a strong likelihood that our approach will increase the timing in which a victim can have a forensic exam performed. Our current assay has been developed "manually," but has high potential for automation. A single forensic examiner could potentially process 400 to 500 samples per day if this automation can be achieved. The current proposal aims to adapt our manual assay to robotic automation. Note: This project contains a research and/or development component, as defined in applicable law. ca/ncf