I am attempting to harvest exosomes from both human bone marrow and adipose MSCs using the ExoQuick-TC kit from System Biosciences. I followed the protocol from the company but after incubation overnight I spun the solution at 1500xg for 30 minutes and did not notice any exosome pellet at the bottom of my tubes. What I did was leave a small amount of supernatant at the bottom after aspiration in the hopes there was an exosome pellet there just not big enough to be visible by the naked eye. Does anybody else have this experience and what were your results?

As a side note I grew the MSCs in T175 flasks with 35mL media before switching to serum free media (serum free to collect exosomes, just DMEM + Glutamax) for 72hrs.