Comparative analysis of two Rapid DNA technologies for the processing of blood and saliva-based samples

An evaluation of the RapidHIT™ ID system for hair roots stained with Diamond™ Nucleic Acid Dye

The RapidHIT™ ID (RHID) system was evaluated for its suitability in processing a single hair root to obtain informative DNA profiles. Hair samples were assessed for nuclear DNA prior to DNA analysis using Diamond™ Nucleic Acid Dye (DD) and real-time Extended Depth of Field (EDF) imaging to visualise and count nuclei if present. Hairs were viewed under an Optico N300F LED Fluorescent Microscope and imaged using a MIchrome 5 Pro camera. Hair roots were processed through both the ACE GlobalFiler™ Express sample cartridge and the RapidINTEL™ sample cartridge. A total of 44 hairs including shed hairs (9) and plucked hairs (35) from 8 donors were evaluated in this study. The processing of hairs using the RHID system required the modification of a standard swab that allowed for hairs to be easily collected and placed into the cartridge but also allowed for the re-collection of hair roots post RHID analysis (for potential standard DNA workflow). 90% of plucked hairs with a high nuclei count (>100) resulted in a high partial or full DNA profile, with the remaining 10% resulting in a low partial profile. 44% of shed hairs resulted in a low partial profile, with the remaining hairs resulting in a null profile. This study demonstrated that the RHID system could successfully obtain a DNA profile from a single hair root with nuclei present post-DD staining. According to these results, it is suggested that when dealing with hairs containing fewer than 50 nuclei, using the RapidINTEL™ cartridge can enhance allele recovery.

Processing biological samples from simulated radiological terrorist events using Rapid DNA instruments

Two commercially available portable Rapid DNA instruments were evaluated for their ability to process 1 µL and 10 µL saliva samples deposited on metal and plastic surfaces and contaminated with surrogates of cesium (Cs)-137, strontium (Sr)-90 and cobalt (Co)-60; radioactive materials potentially released during a nuclear weapon accident or a radiological dispersal device detonation. A comparable success rate was noted for both Rapid DNA instruments when considering the number of complete and balanced DNA profiles, the number of profiles with a minimum of 10 autosomal STR loci (out of 23 [FlexPlex™ 27] or 21 [GlobalFiler™ Express]), and the possibility to search a national DNA database in Canada and the United States. Cobalt had an adverse impact on the quality of the megaplex short tandem repeat (STR) DNA profiles derived on each instrument for two of the three contamination levels tested in this study, i.e., 0.05 M and 0.1 M as reflected by a reduced number of detected alleles and decreased profile peak heights. Strontium exhibited some adverse effect on the Rapid DNA results when used at the highest contamination level (0.1 M) whereas cesium had none. No new artifacts were observed in the Rapid DNA profiles of samples spiked with the non-radiogenic surrogates. Importantly, in the context of a radiological/nuclear (RN) event, the ANDE™ 6C offers the possibility to dispose of all radioactive materials associated with contaminated samples quickly using a chip on which all steps of the Rapid DNA process are performed whereas the RapidHIT™ ID accumulates radioactive materials for many days before disposal. An individual handling 25 samples in a week (5 per day) on the RapidHIT™ ID at a 30.5 cm distance with a 5 min exposure to the radioactive source estimated at every run would exceed the 0.042 µSv/5 min limit with gamma dose rates for Cs at 0.13 mSv and for Co at 3.8 mSv. Beta dose rates calculated for the surrogate isotopes at the three concentrations tested were also above the recommended radiation exposure limit of 1 mSv/yr (0.042 µSv/5 min). Various potential mechanisms of action behind the interference noted for Sr and Co at high concentrations are presented. These elements may play a role in the steps prior to PCR (at the DNA molecule by binding to bases or to phosphate groups), during PCR (at the DNA polymerase as cofactors for catalytic sites), or even during amplified DNA fragment detection (as fluorescence quenchers).