Comparative analysis of DNA collection techniques applied to disposable 3-layer earloop face masks

Since COVID-19 has emerged and become a global health issue, an awareness of wearing face masks has been attentive to prevent the spread of the disease. Face masks that have become a part of daily life, may be encountered at crime scenes and serve as a potential source of DNA for human identification. This study developed a rapid method for obtaining abundant DNA from 3-layer disposable face masks. Ten healthy volunteers were recruited to wear the masks for a period of 2 h. The optimal method for retrieving DNA was determined to be direct cutting of the middle section of the mask's inner layer. The average DNA concentrations from males and females were 0.127 0 ± 0.233 7 ng/μL and 0.069 9 ± 0.107 4 ng/μL, respectively, with no significant difference observed between the sexes (P = 0.286). Furthermore, testing a smaller area (28 cm²) from the mouth-covering region still yielded sufficient DNA for STR genotyping (average 0.025 5 ± 0.021 8 ng/μL). Comparison of the inner and the filter layers revealed that the filter layer contained significantly less DNA (average 0.021 3 ± 0.020 3 ng/μL, P < 0.05). A mockup study was conducted on two female volunteers using six commercial brands of medical, carbon, and super 3D mask types. The results showed that the minimum DNA concentration (0.008 3 ± 0.003 1 ng/μL) extracted from a carbon type is also plenteous for short tandem repeats (STR) genotyping. Finally, mockup samples with low copy number were genotyped and they produced profiles with >19 autosomal STR loci. This suggests that the method was suitable in DNA analysis when a face mask is found as forensic DNA evidence.