exosomes have very low RNA content, so whether you use Trizol, or Total exosome RNA and protein purification kit, or mirVana kit- in all cases you can expect to get a very low RNA amount out of exosomes. For downstream applications that require a lot of RNA (eg sequencing) - we just scale up sample volume, and isolate exosomes eg from 4 ml of blood serum- instead of 100 uL

If you have access to the subjects to collect samples again there are commercial tools which can help to provide a richer sample than that from saliva with no centrifugation required:

 http://www.biotechniques.com/BiotechniquesJournal/2015/February/RNAProSAL-A-device-for-rapid-and-standardized-collection-of-saliva-RNA-and-proteins/biotechniques-356652.html

Dear All,

Thanks a lot for your helpful answers and responses. I am isolating exosomes from conditioned medias of different marophage subpopulations. I will consider preamplification and I will also try growing the cells in a larger volume of media and see how much RNA I can get.  Again thanks a lot for your helpful and timely responses !!

Well, 30 - 40 ng/ul isn't even that bad a yield for EVs... Scaling up the input material is an obvious option, as are including a carrier subtance during RNA extraction and testing different extraction kits (the yield can vary a lot, as shown in the linked paper). If you're limited by the concentration (i.e. volume) of the RNA as opposed to the total yield, you might also try concentrating your sample by drying it down in a speedvac or a similar device.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726450

Thanks a lot Dominik, I will consider drying my samples as suggested.

Hi Ghebremedhin,

I'm trying to isolate exosomes with a precipitating agent followed by manual RNA extraction and i'm getting only 25-15 ng/ul :( . i was wondering about your exosome isolation method ?! and whether you carry out RNA extraction manually or with a kit ?!

Hi Sarah,

I do it manually using a TRIzol reagent from sigma aldrich, I have not used a kit.