A Novel On-Chip Method for Differential Extraction of Sperm in Forensic Cases

Abstract

One out of every six American women has been the victim of a sexual assault in their lifetime. However, the DNA casework backlog continues to increase outpacing the nation's capacity since DNA evidence processing in sexual assault casework remains a bottleneck due to laborious and time-consuming differential extraction of victim's and perpetrator's cells. Additionally, a significant amount (60-90%) of male DNA evidence may be lost with existing procedures. Here, a microfluidic method is developed that selectively captures sperm using a unique oligosaccharide sequence (Sialyl-Lewis(X)), a major carbohydrate ligand for sperm-egg binding. This method is validated with forensic mock samples dating back to 2003, resulting in 70-92% sperm capture efficiency and a 60-92% reduction in epithelial fraction. Captured sperm are then lysed on-chip and sperm DNA is isolated. This method reduces assay-time from 8 h to 80 min, providing an inexpensive alternative to current differential extraction techniques, accelerating identification of suspects and advancing public safety.