Evaluation of Methods to Improve the Extraction and Recovery of DNA from Cotton Swabs for Forensic Analysis
Open Access
- 30 December 2014
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLOS ONE
- Vol. 9 (12), e116351
- https://doi.org/10.1371/journal.pone.0116351
Abstract
Samples for forensic DNA analysis are often collected from a wide variety of objects using cotton or nylon tipped swabs. Testing has shown that significant quantities of DNA are retained on the swab, however, and subsequently lost. When processing evidentiary samples, the recovery of the maximum amount of available DNA is critical, potentially dictating whether a usable profile can be derived from a piece of evidence or not. The QIAamp DNA Investigator extraction kit was used with its recommended protocol for swabs (one hour incubation at 56°C) as a baseline. Results indicate that over 50% of the recoverable DNA may be retained on the cotton swab tip, or otherwise lost, for both blood and buccal cell samples when using this protocol. The protocol’s incubation time and temperature were altered, as was incubating while shaking or stationary to test for increases in recovery efficiency. An additional step was then tested that included periodic re-suspension of the swab tip in the extraction buffer during incubation. Aliquots of liquid blood or a buccal cell suspension were deposited and dried on cotton swabs and compared with swab-less controls. The concentration of DNA in each extract was quantified and STR analysis was performed to assess the quality of the extracted DNA. Stationary incubations and those performed at 65°C did not result in significant gains in DNA yield. Samples incubated for 24 hours yielded less DNA. Increased yields were observed with three and 18 hour incubation periods. Increases in DNA yields were also observed using a swab re-suspension method for both cell types. The swab re-suspension method yielded an average two-fold increase in recovered DNA yield with buccal cells and an average three-fold increase with blood cells. These findings demonstrate that more of the DNA collected on swabs can be recovered with specific protocol alterations.Keywords
This publication has 27 references indexed in Scilit:
- Applicability of DNA Analysis on Adhesive Tape in Forensic CaseworkJournal of Forensic Sciences, 2012
- New Optimized DNA Extraction Protocol for Fingerprints Deposited on a Special Self-Adhesive Security Seal and Other Latent Samples Used for Human Identification*Journal of Forensic Sciences, 2011
- The Utility of Polyester and Cotton as Swabbing Substrates for the Removal of Cellular Material from Surfaces*Journal of Forensic Sciences, 2011
- A Study of PCR Inhibition Mechanisms Using Real Time PCR*,†Journal of Forensic Sciences, 2010
- Effects of Cyanoacrylate Fuming, Time After Recovery, and Location of Biological Material on the Recovery and Analysis of DNA from Post‐Blast Pipe Bomb Fragments*Journal of Forensic Sciences, 2009
- Higher Capillary Electrophoresis Injection Settings as an Efficient Approach to Increase the Sensitivity of STR TypingJournal of Forensic Sciences, 2009
- Simplified Low‐Copy‐Number DNA Analysis by Post‐PCR PurificationJournal of Forensic Sciences, 2007
- Expedited, Chemically Enhanced Sperm Cell Recovery from Cotton Swabs for Rape Kit Analysis*Journal of Forensic Sciences, 2007
- Forensic Applications of DNA TypingAmerican Journal of Forensic Medicine & Pathology, 1998
- Forensic application of DNA ‘fingerprints’Nature, 1985