title: Concentration-Normalized Electroanalytical Assaying of Exosomal Markers.
abstract: Exosomes are both active in mediating intracellular communication and potentially present a potent cargo of disease biomarkers to an assay. The robust evaluation of exosomal markers could lead to a paradigm shift in clinical analysis and associated care. To date, much of this has been hindered by issues of sample preparation and assay signal-to-noise. We introduce here the use of ultrasensitive electrochemical impedance spectroscopy to quantify both external (tetraspanin) and internal (syntenin) exosome-specific markers. Associated exosome detection limits are 1.9 × 105particles mL-1(equivalent to 320 aM or 9500 exosomes in 50 μL) for intact exosomes and 3-5 picomolar for internal exosomal syntenin levels with almost 5 decades of linear dynamic range. Sample preparation can be carried out by simple fine filtering of cell-conditioned medium prior to a non-NTA-determined (i.e., nanoparticle tracking analysis) exosome concentration analysis, lysing, and subsequent internal syntenin quantification. Such concentration-normalized dual-marker analysis can be used to define "analytical zones" in a manner which is then independent of absolute exosome concentration and sample preparation.
authors.affiliation: Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Nuffield Department of Clinical Neurosciences, University of Oxford , John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: George K
authors.initials: GK
authors.lastname: Tofaris
authors.affiliation: Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.forename: Jason J
authors.identifier: 0000-0001-7734-1709
authors.initials: JJ
authors.lastname: Davis
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D058266:Dielectric Spectroscopy; D004566:Electrodes; D055354:Exosomes / Q000378:metabolism*; D006046:Gold / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D057230:Limit of Detection; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism; D053676:Syntenins / Q000032:analysis; D059470:Tetraspanins / Q000032:analysis
chemical_list: D015415:Biomarkers; D053676:Syntenins; D059470:Tetraspanins; D006046:Gold