A Comparison of DNA Collection and Retrieval from Two Swab Types (Cotton and Nylon Flocked Swab) when Processed Using Three QIAGEN Extraction Methods

Abstract

The Metropolitan Police Service currently uses cotton swabs to retrieve DNA for forensic profiling. Recently, a new nylon flocked swab type has become available from Copan (MicroRheologics, Brescia, Italy) that it is claimed, offers increased sample recovery and release yields. If true, the flocked swab may have important applications in DNA evidence retrieval. This study examines the DNA retrieval capability of cotton and nylon flocked swabs when extracted using three common extraction platforms (QIAcube, BioRobot EZ1 and manually processed QIAamp DNA investigator kit). Results indicate that both swab types are capable of recovering high percentages of DNA (>50%); however, the extraction platform selected was shown to have a significant effect upon DNA retrieval. Across all experiments, the cotton swab combined with the spin-column extractions was shown to be most effective, with the nylon swab and BioRobot EZ1 combination being the least effective. These findings illustrate the importance of extraction method selection.

Comparison of an automated nucleic acid extraction system with the column-based procedure

“…= not applicable [11]. E.g., nucleic acid extraction from cotton swabs yields higher DNA percentages in comparison to nylon swabs [10]. Altogether, the extraction quality of the EZ1 system is comparable with other automated extraction systems [11].…”

“…In a recently published comparison of different extraction protocols, the EZ1 system scored best for the extraction of cytomegalovirus DNA from plasma [13]. In another recent comparison of three nucleic acid extraction schemes from cotton and nylon swabs, an assessed EZ1 protocol scored worst in comparison to other approaches with, however, altogether still acceptable performance [10]. In comparison with easyMag (bioMérieux, Nürtingen, Germany) extraction of nucleic acids of respiratory pathogens, the EZ1 system showed a slightly higher detection limit but a considerably lower operational complexity [19].…”

The effect of mark enhancement techniques on the subsequent detection of saliva

“…Quinque et al [69] recovered an average of 11.4 µg/ml with a range of 3.9 -28.7 µg/ml in a sample of 10 individuals. Based on this data and estimating the amount of saliva deposited by each stamp to be 5µl and an average DNA recovery rate from cotton swabs using the QIAamp DNA Blood mini kit of approximately 40% [70], DNA quantities recovered were expected to be between 0.14 -1.04 ng/µl. In this work, DNA quantities recovered ranged from 0.02 -0.23 ng/µl, which were lower than that predicted.…”

A Novel Method for Rapid and Selective Extraction of Male DNA from Rape Kits using Alkaline Lysis and Pressure Cycling Technology (PCT)

“…The results from correlation studies therefore indicate that alkaline lysis coupled with pressure-based extraction gives the best DNA recoveries under 2 hours which includes 15-minute extraction procedure followed by phenol chloroform purification compared to other extraction protocols that include an incubation time ranging between 2 hours and overnight to lyse the cells [13,23,34,48]. But female DNA carryover and loss of male profile is observed when the sample is overwhelmed by fifty times female tissue.…”

“…One of the major limitations of this method is that there is a higher chance of contamination if the filter is not cleaned properly [104,105]. where scientists use dental x-rays, teeth impressions, and bite mark analysis in a range of caseworks encompassing identification of victims in mass disasters [91], identification of the source of bite marks [9], and identification of skeletal remains [23]. Likewise, urine analysis can give important information to a forensic toxicologist pertaining to drugs and toxins ingested by the victim or suspect [42].…”