Transmission electron microscopy assessment of a novel method for isolating pure exosomes from serum

Serum exosomes frequently are used for liquid biopsy. Serum exosomes normally are isolated using ultracentrifugation; however, ultracentrifugation is time-consuming, labor intensive and requires a high-speed centrifuge. Many commercial kits use a precipitation-based method; however, this process can result in substantial contamination. We developed a new method to isolate pure serum exosomes. We isolated serum exosomes using precipitation, extracted them using acetone, then isolated them again by precipitation. We used transmission electron microscopy (TEM) to examine the morphology of serum exosomes. TEM indicated that our isolated exosomes were pure with typical morphology and with a size ranging from 40 to 150 nm. Flow cytometry revealed expression of exosome markers, CD63, CA81 and CD9. Our double precipitation method enables ready extraction of pure exosomes from serum. Our double precipitation method simplifies detection of serum exosomal biomarkers for diagnosis and prognosis of disease.

Automated summary

Serum exosomes are commonly used for liquid biopsy. Traditional methods, such as ultracentrifugation, are time-consuming and labor-intensive. Commercial kits using precipitation can lead to contamination. We developed a new method using double precipitation and acetone extraction to isolate pure serum exosomes with typical morphology and sizes ranging from 40 to 150 nm. Flow cytometry confirmed the expression of exosome markers. Our double precipitation method simplifies the detection of serum exosomal biomarkers for disease diagnosis and prognosis.