Analysis of two novel differential extraction methods
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Citation
Abstract
Fast and effective differential extraction methods are sought to assist in facing the challenge of the backlog of sexual assault evidence in the United States. A differential extraction allows for the separation of epithelial cells from the sperm cells on sexual assault evidentiary samples. In this research, two new differential extraction methods are analyzed and compared for their robustness, accuracy, and ultimate success in the separation of the two cell types. The temperature controlled differential extraction (TCDE) method developed by the Cotton Lab at the Boston University Chobanian and Avedisian School of Medicine uses thermostable enzymes in hopes to increase male DNA recovery in the sperm fraction (SF). This method is a direct lysis approach that produces fractions that can go directly, in many cases, to amplification. The SpermX™ method developed by InnoGenomics© makes use of the different compositions of epithelial and sperm cells by incorporating a built-in sperm-trapping matrix and specialized solutions in their procedure. The membrane allows for sperm cells to be trapped while digested epithelial cells flow through the membrane into an outer tube. InnoGenomics© developed its own tubes to be used in this method so that the evidentiary sample swab is never removed, increasing the potential for DNA recovery, and decreasing the manual manipulations of the evidentiary swab by the analyst. The SpermX™ method also is designed to increase the amount of male DNA recovered in the SF compared to other commonly used methods. In the SpermX™ procedure, DNA purification of the separated cell lysates is need in order to complete downstream DNA analysis.