Quantification of Exosome Based on Copper-Mediated Signal Amplification Strategy

He, Fang, Jing Wang, Bin-Cheng Yin, and Bang-Ce Ye. "Quantification of Exosome Based on Copper-Mediated Signal Amplification Strategy." Analytical chemistry (2018).

Exosomes, a class of small extracellular vesicles, play important roles in various physiological and pathological processes by serving as vehicles for transferring and delivering membrane and cytosolic molecules between cells. Since exosomes widely exist in various body fluids and carry molecular information of their originating cells, they are being regarded as potential noninvasive biomarkers. Nevertheless, the development of convenient and quantitative exosome analysis methods is still technically challenging. Here, we present a low-cost assay for direct capture and rapid detection of exosomes based on copper-mediated signal amplification strategy. The assay involves three steps. First, bulk nanovesicles are magnetically captured by cholesterol-modified magnetic beads (MB) via hydrophobic interaction between cholesterol moieties and li-pid membranes. Second, bead-binding nanovesicles of exosomes with specific membrane protein are anchored with ap-tamer-modified copper oxide nanoparticles (CuO NPs) to form sandwich complexes (MB-exosome-CuO NP). Third, the resultant sandwich complexes are dissolved by acidolysis to turn CuO NP into copper(II) ions (Cu2+), which can be reduced to fluorescent copper nanoparticles (CuNPs) by sodium ascorbate in the presence of poly(thymine) (poly T). The fluores-cence emission of CuNPs increases with the increase of Cu2+ concentration, which is directly proportional to the concen-tration of exosomes. Our method allows quantitative analysis of exosomes in the range of 7.5×104 to 1.5×107 particles/μL with a detection of limit (LOD) of 4.8×104 particles/μL in biological sample. The total working time is about 2 h. The assay has the potential to be a simple and cost-effective method for routine exosome analysis in biological sample.

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