Separating sperm from cell mixtures by using a bubble-based acoustofluidic filtration device for forensic DNA
Hsiao-Lin Hwa1, Ting-Yu Wan2, Chih-Wen Su3
1Department and Graduate Institute of Forensic Medicine, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen Ai Rd., Taipei 100, Taiwan; Department of Obstetrics and Gynecology, National Taiwan University Hospital, No. 8 Chung Shan S. Rd., Taipei 100, Taiwan; Department of Medical Genetics, National Taiwan University Hospital, No. 8 Chung Shan S. Rd., Taipei 100, Taiwan.
Abstract:
Forensic DNA analysis of a victim's oral or vaginal swab containing an offender's sperm is crucial in sexual assault investigations. This study evaluated the effectiveness of a bubble-based acoustofluidic filtration (BAF) device for separating sperm from mixtures of sperm and buccal or vaginal epithelial cells to enhance downstream male DNA contributor analysis. Sperm were separated from 32 two-person (1 man and 1 woman) and 33 three-person (2 men and 1 woman) samples. Autosomal and Amelogenin short tandem repeat genotyping was performed on both pre-BAF and post-BAF samples. Amelogenin Y-to-X allele peak height ratios and mean male-contributor(s)-specific allele peak height proportions were calculated for the pre-BAF and post-BAF samples. Male contributor(s) assignment was conducted using EuroForMix. The Amelogenin Y-to-X allele peak height ratio increased in 90.6% (29/32) of the two-person mixtures and 87.9% (29/33) of the three-person mixtures after BAF processing. The mean male-contributor(s)-specific allele peak height proportion increased in 96.9% (31/32) of the two-person mixtures and 97.0% (32/33) of the three-person mixtures after BAF processing. Male contributor assignment accuracy improved from 93.8% (30/32) to 100% in the two-person samples and from 84.8% (28/33) to 100% in the three-person samples after BAF processing. These results demonstrate that BAF effectively separates sperm from sperm/epithelial cell mixtures and can considerably enhance the accuracy of male DNA contributor identification.
