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

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 disease-specific exosomes using quantum dots as signal amplifiers. The assay involves three subsequent steps where bulk exosome populations are initially magnetically captured on magnetic beads by a generic tetraspanin antibody (e.g., CD9 or CD63) followed by the identification of disease-specific exosomes using cancer-related. Here, we used CdSe quantum dot (CdSeQD) functionalised-biotinylated HER-2 and FAM134B antibodies as breast and colon cancer markers. After magnetic washing and purification steps, acid dissolution of CdSeQDs and subsequent anodic stripping voltammetric quantification of Cd2+ were carried out at the bare glassy carbon working electrode. This method enabled sensitive detection of 100 exosomes per μL with a 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 disease-specific exosomes in clinical samples.Griffith Sciences, School of Natural SciencesNo Full Tex

An amplification-free electrochemical detection of exosomal miRNA-21 in serum samples

Recent evidence suggests that small non-coding RNAs or microRNA (miRNA)s encapsulated in exosomes represent an important mechanism of communication between the cells. Exosomal miRNAs play an important role in oncogenesis via stimulating cell to cell communication and facilitating metastasis in cancers. Despite progressive advances, current methods for exosomal miRNA detection most rely on labor intensive sequencing approaches which are often prone to amplification bias and require costly and bulky equipment. Herein, we report an electrochemical approach for detection of cancer-derived exosomal miRNAs in human serum samples by selectively isolating the target miRNA using magnetic beads pre-functionalized with capture probes and then directly absorbing the targets onto the gold electrode surface. The level of adsorbed miRNA is detected electrochemically in the presence of the [Fe(CN)6]4-/3- redox system. This method enabled an excellent detection sensitivity of 1.0 pM with a relative standard deviation (%RSD) of <5.5% in cancer cells and serum samples (n = 8) collected from patients with colorectal adenocarcinoma. We believe that our approach could be useful for the quantification of exosomal miRNA in clinical samples.Griffith Sciences, School of Natural SciencesNo Full Tex