Isolation and Visible Detection of Tumor-Derived Exosomes from Plasma

Exosomes are nanosized extracellular vesicles (ranging from 30 to 120 nm) released from many cells that provide promising biomarkers for the noninvasive diagnosis of cancer. However, traditional exosome-isolation methods are tedious, nonstandardized, and require bulky instrumentation, thus limiting its clinical applications. In this paper, an anion-exchange (AE)-based isolation method was first proposed to isolate exosomes directly from plasma and cell-culture medium with AE magnetic beads within 30 min. Exosomes isolated with AE magnetic beads had higher recovery efficiency (>90%) and less protein impurities than those isolated by ultracentrifugation (UC). Prostate-cancer (PCa) exosomes in plasma were detected in a visual, label-free, and quantitative manner with aptamer-capped Fe₃O₄ nanoparticles for the first time. The linear range of PCa exosomes was estimated from 0.4 × 10⁸ to 6.0 × 10⁸ particles/mL with a detection limit of 3.58 × 10⁶ particles/mL. The present study provides an efficient and practical approach for the rapid isolation and visible detection of exosomes, which is promising for the early diagnosis of PCa.