*2.15. Quantification of Isolated Exosomes*

Acetylcholinesterase activity assay was performed using EXOCET Exosome Quantitation Kit (System Biosciences, Palo Alto, CA, USA). Isolated exosomes were re-suspended with PBS and lysed with lysis buffer. Each sample was incubated at 37 ◦C for 5 min and mixed with reaction buffer in 96-well plates. Mixed samples were incubated for 20 min at room temperature and quantified by spectrophotometry at OD 405 using standard samples containing known numbers of exosomes. The final number of exosomes was converted to micrograms, per the manufacturer's guideline. To characterize exosomes, isolated exosome preparations were re-suspended with PBS and analyzed using Zetasizer Nano dynamic light scattering system (Malvern Instruments, Malvern, UK).
