Optimizing DNA Extraction from Air Filters: Comparison of PrepFiler versus QIAamp using Saliva and Touch deposits

Environmental DNA (eDNA) captured from air offers a promising avenue for forensic investigations, yet reliable recovery from trace samples depends on optimized collection and extraction protocols. This study compared DNA recovery from two types of filter material, AirPrep™ filters and Corncobology H10 HEPA filter material, using two extraction methods: a modified QIAamp DNA Mini Kit protocol and the PrepFiler™ Forensic DNA Extraction Kit. Filters were loaded with deposits of either saliva or touch DNA, and quarter-sized sections were extracted to enable within-filter comparisons. HEPA filters consistently recovered higher DNA quantities from touch deposits than AirPrep filters across both extraction methods, which may be influenced by differences in surface roughness affecting DNA deposition. While saliva deposits yielded the highest DNA on HEPA filters extracted with QIAamp, Prepfiler produced more consistent recoveries across both filter types, although overall saliva yields were lower. These results highlight that filter structure and extraction chemistry interact to influence DNA recovery, with HEPA filters representing an effective and cost-efficient substrate. Prepfiler offers advantages for laboratories requiring automation and minimized contamination.