By Mike Tayeb on Tue, Nov 27, 2012 @ 10:11 AM
If there's one thing that makes us excited (other than saliva DNA samples, of course), it's seeing samples that are optimized to ensure the best possible results. Great DNA yields from saliva enables our customers to do more with their samples and non-invasive collection options provide researchers and participants with a collection method they actually like. But to get so excited about great DNA samples means there's another end of the spectrum. Therefore, we thought it would be helpful to highlight proven tips and tricks for maximizing your samples.
We know what it takes to get great results from saliva samples and we have years of experience to back that up. We sorted out the top 10 that can really contribute to your success and have compiled them below for your reading pleasure. And while you're reading, ask yourself whether you can learn from any of these or if you have additional tips to share.
Collection based Optimization
- It is important to follow the collection instructions closely. Ensure donors deliver the required amount of saliva and do not eat/drink/smoke/chew gum for 30 minutes prior to giving a sample. Failure to follow these recommendations may result in reduced DNA yield.
- When spitting, bubbles don’t count. Make sure that the liquid saliva is at the ‘Fill To’ line; any bubbles present should be above the line. This will ensure that the optimal amount of saliva is collected.
- DNA yields will vary between donors. It is important to test samples from different donors in order to get an accurate picture of the yields you can expect.
- For donors having trouble spitting 2 ml, saliva flow can often be stimulated by rubbing the cheeks, just behind your back teeth. You can also stimulate saliva production by using a pinch of sugar on the tongue. You only need a tiny amount; just enough that the person can taste it. A drop of lemon juice also works.
- Need to collect from a person unable to spit on command, such as a younger child? Using a collection kit designed for non-spitters, such as the OG-575, will make sample collection easier on both you and the donor and will ensure that you collect enough DNA.
Processing Based Optimization
- The 50°C incubation step must be carried out in the original sample tube, prior to removing an aliquot for DNA extraction. The incubation only needs to be done once; you don’t need to repeat this step when extracting DNA from subsequent aliquots.
- Unless specific steps are taken to remove RNA, RNA will co-purify with DNA. We recommend quantifying your DNA by fluorescence (e.g. Picogreen) since UV absorbance may overestimate the amount of DNA.
- If your downstream application requires high concentrations of DNA, you can increase concentration by reducing the amount of buffer used to dissolve the DNA pellet from 100 µL to 50 µL. It is always easier to dilute the DNA later rather than have to concentrate it.
- Oragene/saliva samples are stable at room temperature for years. If you can’t extract them right away, there is no need to refrigerate or freeze them; just leave them on the bench.
- Ensure sufficient time for DNA to dissolve after extraction. DNA extracted from Oragene/saliva samples using the prepIT•L2P method is extremely high molecular weight and, therefore, will take time to fully dissolve. After extraction, we recommend leaving the sample at room temperature overnight to allow the DNA to fully dissolve. Failure to dissolve the DNA completely may affect quantification and performance in downstream analysis.
These are our top 10. Do you have anything to add to the list? Leave a comment and let us know. You can also subscribe to our blog to receive more articles like this.