Technical Note: A novel method for simultaneous recovery of DNA, RNA, and proteins from trace biological samples for forensic application

Abstract

There is growing interest in recovering analytes other than DNA from evidentiary samples. mRNA markers can help identify body fluids, link body fluid to a contributor via coding SNPs, and estimate Post-Mortem Interval. Proteins, which in many cases are more abundant and resistant to degradation than RNA and DNA, offer the possibility for human individualization via Genetically Variant Peptides and are also useful for body fluid identification, but are routinely destroyed during nucleic acid extraction. We report a novel trace sample recovery method which uses paramagnetic beads conjugated with salmon protamine that bind nucleic acids with very high efficiency under buffer conditions which keep proteins intact. After performing a mild lysis step, nucleic acids are bound to the beads, unbound proteins are collected in the supernatant, and bound nucleic acids are then eluted separately. We demonstrate recovery of DNA, RNA, and protein from 1 µL blood, 1 µL semen, and 2 µL saliva, as well as successful downstream processing using STR DNA profiling, body fluid specific mRNA detection, and protein identification. Amounts of DNA recovered from semen and saliva were on par with a bead-based commercial kit that lacks coordinated RNA and intact protein recovery. Recovered DNA yields from blood were reduced compared to the commercial kit but still sufficient for all downstream processing. RNA amounts recovered were significantly higher in all body fluids using our method. This is the first multianalyte recovery method suitable for trace biological samples, which once validated, will offer forensic scientists the entire suite of molecular analytes for analysis.