Circulating exosomes have been studied as a promising biomarker for non-invasive cancer diagnosis, as they are implicated in tumor initiation, progression, and metastasis. However, the clinical significance of circulating exosomes has not been revealed thoroughly, due to the technical limitation in sensitive and multiplexed detection of cargoes on exosomes, such as proteins and nucleic acids.
University of Kansas researchers have developed an integrated exosome profiling platform (ExoProfile chip) to afford superior sensitivity and multiplexed capability for quantitative detection of a panel of surface protein markers on exosomes. To achieve this goal, they innovatively constructed 3D porous serpentine nanostructures via patterned colloidal self-assembly to provide enormous reaction sites and improve biosensing efficiency of exosomes. Meanwhile, the switchable microfluidic design enabled the simultaneous detection of eight markers on single addition of exosome samples. The ExoProfile chip was validated with purified exosomes from SKOV3 cells, which yielded a limit of detection of 21 exosomes per μL. The researchers applied the ExoProfile chip to clinical analysis of circulating exosomes using only 10 μL ovarian cancer plasma and completing the analysis within 3 h. The diagnostic power of seven markers (EGFR, HER2, CA125, FRα, CD24, EpCAM, and CD9 plus CD63) were evaluated with receiver operator characteristic curve and heatmap clustering. Compared to single biomarker, the combined assessment of a biomarker panel was demonstrated to display improved accuracy in distinguishing early and late stage cancer. The results suggested the ExoProfile chip as a promising platform for molecular fingerprinting of circulating exosomes towards early cancer diagnosis.
(a) Schematic illustration and photo of the ExoProfile chip, consists of pneumatic and fluidic layer and 3D serpentine nanostructures, for in situ immunophenotyping of exosomes. (b) The working principle and flow manipulation of ExoProfile chip in the exosome immunocapture mode and the multiplexed immunodetection mode. Arrows indicated the flow direction. Blue channel: sample injection; green channel: injection of monoclonal detection antibodies (mAbs); black valve/channel: closed valve/channel. (c) The workflow for fabrication of an ExoProfile chip by microfluidic colloidal self-assembly.