Preventing Hydrolytic and Oxidative Damage to Biological Evidence with Antioxidants and Chelators

As submitted by the proposer:

Proper evidence collection and storage techniques are important to protect the integrity of the evidence and prevent/inhibit the growth of bacteria and fungi on evidence; however, it is not always possible to achieve ideal storage conditions for evidence stored for extensive periods of time. Many current forensic evidence collection substrates do not include methods for DNA preservation; therefore, the DNA is left vulnerable to degradation by hydrolytic or oxidative forces. If biological evidence is protected from hydrolytic and oxidative damage, storage of evidence may occur for years without compromising the integrity of the DNA.

The goal of this proposal is to expand upon the work performed under NIJ Grant #2010-DN-BX-K193 by preventing hydrolytic and oxidative damage to DNA evidence through the use of antioxidants and chelators. These techniques are intended for use by the forensic investigator at a crime scene, so non-hazardous and naturally occurring preservatives will be examined. The following chelators and antioxidants will be investigated: ehylenediaminetetraacetic acid (EDTA), diethylenetriamine pentaacetic acid (DTPA), desferrioxamine (DFOA), zinc, astaxanthin, hydroxytyrosol, and á-tocopherol. Preservatives will be applied to biological samples on swabs, and they will be stored at room temperature, 37°C, and 50°C with ambient humidity conditions or 75-85% humidity for 183 days, 365 days, and 548 days. A total of 2,571 samples will be examined. The forensic DNA profile index will be used to analyze the profile quality. To determine if significant differences were generated between the treated samples and controls, the F-Test for Variance and Student’s T-test will be employed.

Additionally, six application devices/methods for depositing the preservatives on collection devices will be evaluated. Evaluation of the application devices/methods will address three objectives: assess the preservative coverage provided by each application device; evaluate the ease of use of each application device; and determine if the preservatives retain their efficacy when deposited on swabs with the various application devices/methods.

At the end of this effort, the best methods for preserving biological evidence will be selected. These methods can then be employed by the law enforcement community to protect biological evidence from hydrolytic and oxidative damage. The work performed on this project will be disseminated to the forensic community through publications and presentations at scientific meetings.

This project contains a research and/or development component, as defined in applicable law.

ca/ncf