An Electrochemical Method for the Detection of Disease‐Specific Exosomes

Abstract

Exosomes are cell‐derived vesicles secreted by both normal and cancerous cells into the extracellular matrix and in blood circulation. Tumor‐derived exosomes have attracted increasing attention in noninvasive cancer diagnosis and prognosis. However, their effective capture and specific detection pose significant technical challenges. Current detection methods largely fail to quantify the tumor‐derived exosomes present in the total (bulk) exosome population derived from body fluids of cancer patients. In this proof‐of‐concept study, we report an electrochemical detection method to directly quantify the disease‐specific exosomes present in cell culture media. The assay has a two‐step design, where bulk exosome populations are initially captured by using a generic antibody (i.e. tetraspanin biomarker, CD9). Subsequent detection of the cancer‐specific exosomes within the captured exosomes was carried out by using a cancer‐specific antibody, in this case, a human epidermal growth factor receptor 2 (HER‐2) antibody, allowing quantification of HER2‐postive, breast‐cancer‐derived exosomes. This approach exhibits excellent specificity for HER‐2(+) BT‐474 cell‐derived exosomes (detection limit, 4.7×105 exosomes μL−1) with a relative standard deviation of <4.9 % (n=3). We suggest that this simple and inexpensive electrochemical method could be an alternative for the quantification of exosome subpopulations in specific disease settings for future clinical bioassays.

Microfluidics for exosome isolation and analysis: enabling liquid biopsy for personalized medicine

“…44,50,55–58 Other detection techniques, such as plasmonic and electrochemical sensing platforms, have also been applied in conjunction with immunoassays to achieve high throughput, easy-to-use, and label-free protein analysis. 44,59–61 Finally, nucleic acid content can be probed by first applying conventional isolation methods, after which analysis is performed by either polymerase chain reaction (PCR) or sequencing techniques. 62–64 …”

Biological Functions and Current Advances in Isolation and Detection Strategies for Exosome Nanovesicles

“…Photograph of the qNano analyzer and concentration of exosome population derived from A) HER‐2(+) BT‐474 and B) HER‐2(−) MDA‐MB‐231 breast cancer cell lines. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…Although recent progress has improved the isolation efficiency of exosomes from other extracellular vesicles, there are only few reported strategies that describe the efficient detection of disease‐specific exosomes in the background of normal exosomes (i.e., exosomes that can be derived from both normal and diseased cells from the same subject) . It is now widely acknowledged that exosomal cargo, which is encapsulated in the protective layer of the exosome membrane, is a promising source of biomarkers for disease diagnosis and prognosis.…”

“…Lobb et al used TRPS to obtain measurements for the exosome concentrations after isolating the nanosized vesicles using various protocols . More recently, Sina et al and Yadav et al reported the use of TRPS for the characterization of breast cancer‐derived exosomes prior to quantifying them with surface plasmon resonance and electrochemical readouts, respectively. qNano has shown great promise as a reliable tool for accurate exosome quantification.…”

“…For instance, while conventional ELISA suffers from long assay times, laborious sample loading, reagent addition, washing and incubation steps, a modified ELISA integrated with a lab‐on‐a‐chip microfluidic platform offers a simple, fast, and automated analysis of exosomes . Much attention has also been given to developing new strategies based on microfluidics and electrochemical biosensors . Among these, electrochemical biosensor approaches have shown great promise due to their fast, simple, and cost‐effective procedures, as well as the requirement for less sample volume.…”