Session: Analytical Division Student Poster Session: Celebrating the Research of Minority Undergraduate and Graduate Students:

Tumor-derived exosomes are considered as potential biomarkers for early non-invasive cancer diagnosis. Although quite a few methods have been reported for quantitative detection of exosomes, the nanoparticle tracking analysis (NTA) and BCA protein assay are most commonly employed. However, NTA instrument is expensive and requires a large volume of sample, preventing its widespread application. Whereas BCA assay will lead to inaccurate results due to heteroproteins obtained during isolation process. Therefore, it is still necessary to develop more practical and accurate methods for quantification of exosomes derived from various samples.

Here, we designed a PDMS microfluidic chip with a simple cross channel (figure1). The depth of both channels is 600 um and all channels and wells are open to the air for convenient manipulation. First, 3% of agarose was injected into the gel channel and the other channel was filled with TAE buffer only. After that, 10 μL of exosomes (from A375 cell line) pre-stained with PKH67 dye was injected into the sample well. Fluorescence intensity was recorded by a home-made detection system.When a voltage of 100V was applied at the both end wells of electrophoresis channel, the PKH67 stained exosomes migrated to the anode which were found not able to enter 3% agarose gel in short time, thus enriched at the interface of the gel/buffer. Accordingly, the fluorescence intensity of exosomes was accumulated as well. Under optimized conditions, a linear range of 2×10⁷-1×10¹¹ particles/mL is obtained and 1×10⁷ particles/mL of detection of limit (LOD) was achieved.

In summary, we proposed a simple and practical method as a universal tool for quantitative detection of exosomes. The process of electrophoresis and detection was within 10 minutes and the performance is equal to NTA. But only 10 μL of exosome sample was required.

Schematic of PDMS chip for rapid enrichment and detection of exosomes (A); Fluorescence intensity of different concentration of exosomes (B); Standard curve and linear range of this assay (C)

Schematic of PDMS chip for rapid enrichment and detection of exosomes (A); Fluorescence intensity of different concentration of exosomes (B); Standard curve and linear range of this assay (C)

Danyang Sun

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