The DNA DipStick Kit is essentially a Southern blot on a stick. This kit allows you to estimate the amount of ssDNA, dsDNA, RNA or oligonucleotides (of 6 bases or more) in a sample of interest. The range for accurate measurement is from 0.1-10ng/uL. This kit has many potential applications including cDNA library construction, PCR and RT-PCR, RFLP, RNA transcription and DNA sequencing.
In the kit I tested there were 50 sticks. The other reagents included in the kit are wash solution (60mL), coupling solution (60mL), developer stock (60mL), developer (4mL), 6 reaction cuvettes, a DNA standard (100ng) and a reference card giving brief instructions and images of what your standards should look like. This kit suggests that several dilutions of your DNA extract should be made (1:10 and 1:100) so that your results should be in the reference range shown on the card. 1uL of each dilution is placed on the stick (not touching one another). I was able to get two samples on each stick, which effectively cuts the cost of each test in half. The DNA standards should be diluted out to 10ng/uL, 1ng/uL and 0.1ng/uL, but they can also be set up as per the reference card to see if you are getting the correct resolution.
Once the 1uL of sample is added, the sticks should air dry for at least 5 min (can be sped up using a light source). Next you label 3 cuvettes and independently add 1mL of wash solution, 1mL of coupling solution and 1 drop of developer plus 1mL of developer stock (be sure to mix developer solution). When dry, you put prepared stick vertically into the wash solution for 10 sec, remove and place in the coupling solution for 3 min and then rinse in deionized water for 20 sec. Following the rinse, place the stick back into the wash solution for 4 min followed by 2 min in the developer/developer stock mix. Finally, gently rinse the stick in wash solution for 20 sec and allow it to dry. After the DipStick dries then you can read the results. The manual suggests that you then discard the reagents and use fresh ones for the next stick. However, I have found that putting two sticks vertically in the cuvette with the membranes facing each other from opposite sides of the cuvette works as well, saving reagents.
Reading the results is a fairly subjective matter unless you set up a large range for your standards e.g. 0.1-10. Obviously this is not practical. The reference card gives you 5 concentrations (0.1, 0.5, 1, 5, and greater than 10). The range can easily be tested if it is set up as 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5 and greater than 10. This would take up 2 sticks if you manage to fit 6 spots per strip, while enabling you to get a better range for judging the quantity of nucleic acids. These sticks can then be used for future reference, as they are not supposed to fade with time. If you happen to run out of sticks and still have plenty of reagents left you can use nitrocellulose paper stuck onto thin off-cuts from laminating paper or laminate a pouch without paper inside and cut them to your desired length and width. I have not had any problems deviating in this way from the recommended protocol, so far.
The results obtained by this method are pretty subjective. However, if you only need the DNA to be within a certain range for your application (such as DNA sequencing or microsattelite analysis) it should not be a problem. As long as you know your sample is pure, this kit is a quick means to obtain results. There are some substances that interfere with this test (such as molecular biology grade agarose, SDS, Herring sperm DNA and tRNA). Surprisingly, crude preparations of phage DNA do not interfere with the test.
David Fegredo
Medical Scientist
PathWest
Australia