Forensic DNA Extraction : Validation Complete
We have successfully completed the validation and implementation of our DNA Extraction process using the Qiagen EZ1 Advanced XL (right) and the Qiagen Qiacube Connect (left). These instruments and processes are now approved for Forensic DNA Casework. We'd like to thank Bryan Davis, Mark Guilliano and Josh Abernathy from Qiagen for all the support and assistance getting us up and running. Remember... our two EZ1 advanced XL instruments were generously donated by the Qiagen company and we cannot thank them enough!
In the spirit of transparency, we have also created a page on our website devoted to our finalized validation summaries. I invite anyone to review and comment and if it is helpful, please feel free to use our data or processing ideas in any way that would be helpful to you or your laboratories. You can find our validations here:
They can also be selected by going to our "resources" tab of our home page and selecting the "Validations" link.
For those of you that are new to Forensic DNA Extraction using the EZ1 Advanced XL, I'd like to go into a bit of details on what this instrument does. DNA Extraction can be thought of as 1) "popping" cells (Lysis), 2) isolating the DNA from within the cells and removing all of the other cellular material "junk" as well as any other materials like dirt or cotton swab material (Purification).
The EZ1 does this by capturing DNA on magnetic beads, using a magnet to hold the bead/DNA while it washes out all the extra "junk" and finally releasing the purified DNA from the magnet in about 40ul of water into a tube now known as a DNA extract! Here's a great youtube video about Magnetic Bead DNA extraction: The Qiagen Qiacube Liquid Handling Robot is also within this validation. This helps us automate a process called Differential Extraction, which is extremely important for sexual assault evidence. It separates sperm cells from other cells (blood, saliva/vaginal epithelial (skin) cells) and allows us to make two DNA extracts, one from the sperm cells and another from the "other" cells. If, as an example, a vaginal swab was taken during collection of a sexual assault kit, the vaginal cells from the victim would end up in one fraction and the sperm cells from the suspect in another. This helps us get sperm cell DNA profiles very effectively. In differential extraction, we first "pop" the epithelial or skin cells without disturbing/popping open the sperm cells. The DNA from these cells are removed from the sample and purified (with the EZ1 advanced XL as above) in the epithelial cell fraction. Because sperm cells are more difficult to "pop" they remain in the initial sample tube. They are then rinsed 3-5 times to wash out all of the remaining epithelial cell DNA.
The sperm cells are then "popped" by adding a substance called DTT that helps break them open. This is also purified and delineated as the sperm cell fraction. Both samples, epithelial cell fraction and sperm cell fraction can then continue on in the forensic DNA process. The Qiacube automates this process, improving our efficiency and removing some potential for human error. We intend to provide a much more in depth education on this in the future in a series of DNA 101 type articles, so stay tuned. The moral of this story is that we're ready to do DNA extraction on our samples! The quantification validation is next and should be reviewed and available before the end of the week. Progress!