Progress in the field of forensic DNA profiling

Collecting biological fluid samples on a solid matrix is a standard method in both newborn screening and forensics. Blood spot collection on 903 filter paper for newborn screening was first described by Dr. Robert Guthrie in 1963.¹ Heel-stick blood samples were blotted onto 903 filter paper and signature metabolites tested for diagnosing inborn errors of metabolism. Later McCabe et al. (1987) discovered that DNA could be extracted from these dried blood spots (DBS).² As a result, DBS technology quickly became adopted as a simple means of obtaining DNA samples for human genetics and forensic DNA identification.

While metabolites in dried blood samples, such as those measured in newborn screening tests, are often stable, DNA undergoes degradation over time. In addition, if blood samples are not dried and stored properly at low temperature, they can become contaminated with microorganisms that make DNA analysis impossible. These observations led researchers at Flinders University in Australia to develop a unique chemical treatment of solid matrices that can stabilize DNA at room temperature. The chemically coated matrix, FTA, also circumvented the problem of DNA contamination by inhibiting growth of both bacteria and mold, which was a common problem when samples were kept under conditions of high heat and humidity or were improperly collected. The benefits of DNA stabilization and long term room temperature storage for genetic identification were immediately apparent and led to the FTA matrix being quickly adopted by the forensic community for collecting blood samples for DNA analysis.

Benefits of FTA

1. FTA preserves and stabilizes DNA, preventing environmentally induced degradation.
In a series of experiments conducted by the Midwest Research Institute (MRI), DNA on an FTA treated and an untreated matrix was challenged with a UV source to induce the sample aging process; DNA degradation was measured using real-time PCR After UV treatment there was a 2-fold loss of DNA on the FTA treated matrix whereas there was a greater than 850 fold loss of DNA on the untreated matrix.

2. FTA allows for the room-temperature storage of biological samples for DNA analysis.
Blood samples stored on FTA matrices at room temperature for over 17 years were tested at the University of North Texas Health Science Center, DNA Identification Lab for the ability to undergo PCR amplification for Short Tandem Repeat (STR) analysis and were found to be fully profiled without stutter, peak drop-ins/outs, or peak imbalance.