As the fields of aging and neurological disease expand to liquid biopsies, there is a need to identify informative biomarkers for the diagnosis of neurodegeneration and other age-related disorders such as cancers. A means of high-throughput screening of biomolecules relevant to aging can facilitate this discovery in complex biofluids, such as blood. Exosomes, the smallest of extracellular vesicles, are found in many biofluids and, in recent years, have been found to be excellent candidates as liquid biopsy biomarkers due to their participation in intercellular communication and various pathologies such as cancer metastasis. Recently, exosomes have emerged as novel biomarkers for age-related diseases. Hence, the study of exosomes, their protein and genetic cargo can serve as early biomarkers for age-associated pathologies, especially neurodegenerative diseases. However, a disadvantage of exosome studies includes a lack in standardization of isolating, detecting, and profiling exosomes for downstream analysis. Researchers from the Claremont Colleges discuss current techniques for high-throughput isolation and detection of exosomes through various microfluidic and biosensing strategies and how they may be adapted for the detection of biomarkers of age-associated disorders.
Colorimetric, surface-functionalized biosensing of exosomes
(A) Aptamer-based biosensor utilizing singlewalled carbon nanotubes (s-SWCNTs) for immunocapture of exosomes with CD63 and subsequent colorimetric 3,3′,5,5′- tetramethylbenzidine (TMB) assay. (Bi) ZnO-based biosensor applying ZnO nanowires, polydimethylsiloxane (PDMS) scaffold structure with ZnO nanocrystals forming nanowires. (Bii) SEM of ZnO nanowires on the scaffold. (Biii) SEM image of exosome capture. (Biv) Colorimetric assay example with and without exosomes with sandwiched immunocapture of CD9 and CD63 functionalized ZnO nanowires (reprinted with permission from Copyright Clearance (2016) and (2017) Elsevier). (Ci) Schematic of a double-filtration microfluidic device for size-based exosome isolation featuring the initial 200 nm membrane and subsequent 30 nm membrane. (Cii) Schematic of direct enzyme-linked immunosorbent assay (ELISA) for extracellular vesicle (EV) detection with on-chip ELISA. (Ciii) Detection of colorimetric HRP-TMB interaction with smartphone and computer. Reprinted with permission from Copyright Clearance (2017) Nature Scientific Reports.