Effect of pH on the isolation of urinary exosome

Urinary exosome is an ideal noninvasive, low-cost source of kidney diseases biomarkers. However, many factors effect the isolation of urine-derived exosome. The effect of pH on the yield of exosome isolation under different pH was explored. The pH was adjusted for 4, 5, 6, 7 and 8 with hydrochloric acid and sodium hydroxide solution. All samples were incubated for 30 min before differential ultracentrifugation. Exosome-associated protein markers TSG101, ALIX and total concentration of RNA were evaluated by Western-blotting and micro-amount ultraviolet spectrophotometer, respectively. A major loss of urinary exosome was received at pH 8 compared with alkali medium or control group. There was no difference whether or not added EDTA-Na-2. Acidic environment was likely to conducive to the isolation of exosome and maintain its stability and integrity that suggest pH medium needs to be carefully considered and also provide a methodology for future separation exosome.