![]() ![]() However, such indirect detection is not quantitative and measurements are further complicated due to aggregation of exosome-bead complexes. Alternatively, immunocapturing of exosomes on antibody coated beads 16 facilitates analysis by FC. Exosomes have diameters in the range from 30–100 nanometers, i.e., which is too small to be accurately sized by conventional methods such as optical microscopy and flow cytometry (FC) without labels. ![]() The limited utility of exosomes in diagnostics is mainly due to difficulties in specifically characterizing them using a scalable phenotyping method. In human CSF, EVs are rich reservoirs of biomarkers for neurological disorders and there is increasing evidence that deregulation of EVs secretion play a pathological role in neurodegenerative diseases such as Alzheimer’s disease (AD) and Frontotemporal dementia (FTD) 11, 12, 13, 14, 15. In particular, EVs are considered valuable for liquid biopsies in cancer diagnosis since they carry molecular and proteomic cargo from their tumour cell of origin 10. Presence of exosomes in circulating bodily fluids, including blood 3, urine 4 and saliva 5, suggests that minimally-invasive diagnosis of a number of diseases can be achieved through detection of these vesicles 6, 7, 8, 9. The interest of scientists and physicians in EVs has grown dramatically over the past decade in response to the discovery that these vesicles transfer mRNA, miRNA, and protein from the cell of origin to recipient cells 2, serving a new route for cell-to-cell communication. Similar content being viewed by othersĮxosomes are a class of membranous extracellular vesicles (EV) that originate from inward budding of the endosomal compartment within a cell 1. With this unprecedented capability, we foresee revolutionary implications in the clinical field with improvements in diagnosis and stratification of patients affected by different disorders. Our interferometric imaging method could capture, from a very small hCSF volume (20 uL), nanoparticles that have a size compatible with exosomes, using antibodies directed against tetraspanins. As a demonstration of clinical utility, we characterize exosomes directly from human cerebrospinal fluid (hCSF). We demonstrate these characterization concepts using purified exosomes from a HEK 293 cell culture. In this work we present a method based on Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS) that allows multiplexed phenotyping and digital counting of various populations of individual exosomes (>50 nm) captured on a microarray-based solid phase chip. The small size (30–100 nm) along with low refractive index contrast of exosomes makes direct characterization and phenotypical classification very difficult. Exosomes, which are membranous nanovesicles, are actively released by cells and have been attributed to roles in cell-cell communication, cancer metastasis, and early disease diagnostics. ![]()
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