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Why is DNA Purification Essential for Cannabis Microbial Testing?

In order to get accurate, reproducible results, you must remove cannabis compounds that may inhibit PCR reactions.

Computer scientists and mathematicians use the saying “garbage in, garbage out” to explain that the quality of a result is dependent on the quality of the input. When incorrect or incomplete data is input to a program, the output is not going to be accurate.

The same applies to qPCR testing. In order to get accurate, reproducible results, you must remove the “garbage” (i.e, compromise and material that may compromise the reaction). This is especially relevant in cannabis flower samples, which contain thousands of lipid-rich compounds.

DNA Extraction vs DNA Purification

Most DNA Extraction methods involve placing a sample into a lysis solution and heating it to break open cell walls and expose the DNA within. That lysis solution is then transferred into the qPCR reaction, along with any other compounds that may be present in the sample. 

DNA Purification methods take this process one step further and remove any additional compounds or cellular material from the sample. This greatly reduces the number of inconclusive results and re-runs. 

How does SenSATIVAx Purify DNA? 

Following the lysis step, MGC Binding Buffer, which contains millions of tiny magnetic beads, is added to the lysis solution. The magnetic beads bind to the hydrophilic (water-loving) DNA, and when the plate is placed onto a magnet, the beads and the DNA form a ring at the bottom of the well (see below). This allows the lab technician the opportunity to wash away any lipophilic (fat-loving) compounds, leaving only the DNA behind. 

In what cases is DNA Extraction Appropriate? 

Simple DNA extraction is an adequate approach for tests where the user expects there to be a large amount of target DNA. For example, we recommend a simple DNA extraction for our FemINDICAtor qPCR Plant Sex Test because we know there will be a large amount of target DNA in any male plants. 

However, when testing for microbial contamination, the amount of target DNA is variable and often in a much lower concentration than plant DNA. Furthermore, microbial testing is performed to ensure consumer safety, and in those cases, you don’t want anything that may compromise the accuracy or sensitivity of the test. 

Great Results start with Great DNA

When it comes to patient safety and microbial safety testing, simple DNA extraction isn't enough. If you're using a "simple" lysis extraction method, take a closer at the user guide. You may see a note that states:

"Cannabis flower is known to cause PCR inhibition. It is highly recommended to purify the DNA extract to avoid inhibition." 

We couldn't agree more and its why our team developed the SenSATIVAx kit specifically  for the cannabis and hemp flower matrices.