RNA purification sample preparation guidelines

Read our guidelines detailing RNA purification sample preparation for your FirePlex® miRNA assay.​

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FirePlex miRNA Assay

For optimal results load between 0.1–5.0 ng of total RNA in a 25 µL volume per well, or add 40 µL plasma/serum to the digest step.

RNA isolation methods for different starting material are below:

Plasma or serum samples

For best results, store the sample at -80°C and limit the number of freeze/thaws that the samples undergo prior to quantification with the FirePlex miRNA Assay.

Isolated total RNA from cells and tissues

For best results, use any of the methods recommended for the FirePlex miRNA Assay.

Isolated total RNA from plasma or serum

For best results, isolate total RNA from plasma or serum using the TRIzol-LS®​ standard protocol as applied to 250 µL of sample, with 1 µL 15 mg/mL GlycoBlue™ added prior to precipitation. After precipitation with isopropanol, wash once with 75% ethanol then dry the pellet and resuspend in 50 µL RNase-free water. We suggest that 40 µL sample-equivalents be run (i.e. 8 µL of the 50 µL + 17 µL RNase-free water = 25 µL sample for assay).

Caution: For any column-based RNA isolation methodology, please confirm that the protocol you are using does not select against small RNAs. It is important to carefully follow the manufacturer's recommendations regarding ethanol concentration during wash and rinse steps to ensure that miRNAs are not excluded from the final product. Also, regardless of isolation method, it is important that the RNA be resuspended in RNase-free water or 1X TE to keep salt to a minimum.

Quantification of RNA from samples such as 250 µL plasma/serum will be impossible using absorbance-based technologies including Nanodrop and may be unreliable from more sensitive technologies such as Promega Quantus. Reliable profiling of miRNAs using the FirePlex miRNA Assay can be performed even on samples that are not adequately quantified.