Enhanced elution of sperm from cotton swabs via enzymatic digestion for rape kit analysis

This report describes development of a method for enhanced cell elution from cotton swabs. The method exploits an enzyme mixture for digestion of the cotton to remove intact cells, and can be utilized in conjunction with or to circumvent conventional differential extraction (DE). Samples digested with Aspergillus niger cellulase yielded sperm cell recoveries (18+/-3.5%) similar to conventional DE buffer (23+/-7.8%) while providing intact epithelial cells. Storage time affected the concentration of enzyme required for optimal sperm cell recovery, with longer times requiring increased cellulase concentrations. Cellulase from A. niger yielded a twofold enhancement in sperm cell elution over buffer alone, and preliminary testing of higher activity cellulases from Trichoderma reesei and Trichoderma viride showed even greater enhancement. These results indicate that cellulose-digesting enzymes enhance the release of sperm and epithelial cells from a cotton swab over buffer alone, providing for efficient DNA analysis.