Maximizing the amount of DNA recovered: a study of Mawi DNA technologies' iSWAB-ID collection device for forensic science application
Gordon, Michelle Kristen
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In forensic casework, recovery of more deoxyribonucleic acid (DNA) generally leads to a better chance of obtaining a robust and reliable DNA profile. However, DNA evidence often contains a very low amount of cells, therefore, the importance of proper collection and storage to protect the DNA and ensure that maximum collection of cells is achieved cannot be over emphasized. New techniques and inventions have made the collection of DNA evidence more efficient and consistent through the development of different types of swabs, lysing buffers and various other improvements. Even with the development of these improvements, the ability to maximize the collection of cellular material from a substrate is still impeded by various issues in the extraction process along with the structural properties of swabs used for collection. Research by Adamowicz et al. found that when extracting buccal and blood cell samples collected on cotton swabs, using the recommended protocol for swabs with the QIAamp DNA Investigator extraction kit, over 50% of the recoverable DNA is retained on the swab or lost through the extraction process . Although cotton swabs are very good at absorbing biological material, they exhibit low efficiency of DNA sample release. Additional DNA may be lost during the extraction process. An optimal method of collection and extraction for forensic samples will maximize the collection and release of cellular material and minimize the loss of cellular DNA in the extraction process. The design of the Mawi DNA Technologies’ iSWABTM collection device allows for the release of cells captured from any type of swab into a proprietary lysis and stabilizing iSWABTM buffer. The combination of the mechanistic release of cells and the proprietary lysis buffer claims to maximize the collection of cells from single or several swabs in a pre-measured amount of buffer while eliminating the potential for bacterial growth and contamination. The iSWABTM Device is designed with three prongs and contains cell lysis buffer with DNA stabilization chemistry. As the swab is taken out of the collection device, the prongs provide resistance and essentially squeeze the excess solution and cells off of the swab. Following collection of the cellular material, cell lysis is achieved by incubation in the lysis buffer for 3 hours at room temperature. No additional reagents are necessary. This study investigated whether the Mawi DNA Technologies’ iSWABTM collection device and buffer could be considered as an alternative method to maximize the recovery of cells/DNA from swabs. Experiments were conducted to test the efficiency and forensic application of the device. The following parameters of the iSWABTM buffer and collection device were tested: 1) ability to collect dried stains; 2) ability to recover cellular material from different types and conditions of swabs; 3) ability to lyse different cell types; 4) ability to stabilize DNA over an extended period of time; and, 5) ability to perform in downstream Polymerase Chain Reaction (PCR) testing and produce quality STR profiles. Cumulatively, the data indicates that the iSWABTM-ID collection device is simple, fast and convenient while providing high DNA recovery. Some modifications or additional procedure developments can be done to facilitate the application for use with samples containing very small amounts of biological materials.