Disclosed are methods, compositions, devices, and kits for the isolation of brain- specific exosomes. Specifically, methods, compositions, devices, and kits comprising an isolated brain-specific extracellular vesicle or exosome joined to a first binding agent that is specific for tau, β-amyloid, S100 β, neuron-specific enolase, glycoprotein A2B5, CD133, NQ01, synaptophysin, neuronal nuclei, MAB1569, polysialic acid-neural cell adhesion molecule (PSA-NCAM), or neurogenic differentiation 1 (NeuroD or Beta2), or glycosylated or phosphorylated forms of these molecules, are provided.
