Detecting Exosomes Specifically: A Multiplexed Device Based on Alternating Current Electrohydrodynamic Induced Nanoshearing

Abstract

Exosomes show promise as noninvasive biomarkers for cancer, but their effective capture and specific detection is a significant challenge. Herein, we report a multiplexed microfluidic device for highly specific capture and detection of multiple exosome targets using a tunable alternating current electrohydrodynamic (ac-EHD) methodology, referred to as nanoshearing. In our system, electrical body forces generated by ac-EHD act within nanometers of an electrode surface (i.e., within the electrical layer) to generate nanoscaled fluid flow that enhances the specificity of capture and also reduce nonspecific adsorption of weakly bound molecules from the electrode surface. This approach demonstrates the analysis of exosomes derived from cells expressing human epidermal growth factor receptor 2 (HER2) and prostate specific antigen (PSA), and is also capable of specifically isolating exosomes from breast cancer patient samples. The device also exhibited a 3-fold enhancement in detection sensitivity in comparison to hydrodynamic flow based assays (LOD 2760 exosomes/μL for ac-EHD vs LOD 8300 exosomes/μL for hydrodynamic flow; (n = 3)). We propose this approach can potentially have relevance as a simple and rapid quantification tool to analyze exosome targets in biological applications.

Microfluidics‐based on‐a‐chip systems for isolating and analysing extracellular vesicles

“…Kanwar et al efficiently captured circulating EVs using the “ExoChip” platform [76]. Moreover, with continual advances in nanotechnology such as nanoshearing effects [81] and nanostructured interfaces [82], the sensitivity and specificity of Mf-IAC devices has been substantially improved. For instance, Zhang et al produced a Y-shaped micropost nanostructured interface to enhance the capture surface area [82], while Kang et al designed a device that can generate mechanical whirling to increase the probability of binding between the antibody and the EVs [83].…”

Advances in liquid biopsy on-chip for cancer management: Technologies, biomarkers, and clinical analysis

“…Many exosome capture methods have been developed on-chip to counter these poor yields and process time. Physical filtration by ciliated micropillars [42], immunomagnetic isolation [30], [91], [92], immunoisolation on beads [93], and immuno-affinity with nanoshearing [94] are some of the methods used for the capture of exosomes on-chip. As for on-chip analysis of exosomal biomarkers, there are many advantages when compared to standard protocols, including high throughput, sensitivity, and automation.…”

“…As for on-chip analysis of exosomal biomarkers, there are many advantages when compared to standard protocols, including high throughput, sensitivity, and automation. Analysis of surface proteins [30], immunoelectrophoresis [95], colorimetric [94], qPCR [92], on-chip ELISA detection [46], and mass quantitation [96] are some of analytical methods offered on-chip for exosome characterization. We will discuss in-depth some of the more interesting cases.…”

Bulk immunoassays for analysis of extracellular vesicles

“…ac-EHD is an ELISA-based assay in a microfluidic chip, in which capture of EV is enhanced 3-fold by a local flow induced by an electric field [24].…”

“…Enzyme-based detection has been demonstrated [24], but there is no fundamental limitation to the application of fluorescence or phosphorescence.…”