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Quantum dot-based sensitive detection of disease specific exosome in serum

Boriachek, K., Islam, M. N., Gopalan, V., Lam, A. K., Nguyen, N. T., & Shiddiky, M. J. (2017). Quantum dot-based sensitive detection of disease specific exosome in serum. Analyst.

Tumor-derived exosomes have emerged as promising cancer biomarkers due to their unique composition and functions. Herein, we report a stripping voltammetric immunoassay for the electrochemical detection of tumor-specific exosomes using quantum dots as signal amplifier. The assay involves three subsequent steps where bulk exosome populations were initially magnetically captured on magnetic beads by a generic tetraspanin antibody (e.g., CD9 or CD63) followed by the identification of cancer-specific exosomes using cancer-specific antibodies. Here, we used CdSe quantum dots (CdSeQDs) functionalised-biotinylated HER-2 and FAM134B antibodies as breast and colon cancer-specific markers. After magnetic washing and purifications steps, acid dissolution of CdSeQDs and subsequent anodic stripping voltammetric quantification of Cd2+ were carried out at bare glassy carbon working electrode. This method enabled sensitive detection of 100 exosomes/┬ÁL with the relative standard deviation (%RSD) of <5.5% in cancer cell lines and a small cohort of serum samples (n=9) collected from patients with colorectal adenocarcinoma. We believe that our approach could potentially represent an effective bioassay for the quantification of tumor-specific exosomes in clinical samples.

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