For determining the protein amount in cells and in EVs, the Pierce™ BCA Protein Assay Kits was used according to the manufacturer's instructions. In short, albumin standards (2000, 1500, 1000, 750, 500, 250, 125, 25, 0 µg/mL) were prepared by dilution of the 2.0 mg/mL bovine albumin serum (BSA) with PBS. Working reagent (WR) was prepared by mixing 50 parts BCA Reagent A with 1 part of BCA Reagent B. The cleaned cell solution was diluted 1:5 to achieve a concentration in the range of the assay and EVs were measured as prepared.