(1) MUS:OT NPs Successfully Label Different Polymorphs of Amyloid Fibrils.(2) MUS:OT NPs Enable Rapid Profiling and Characterization of the Polymorphism of the AD-Associated Aβ40 and Tau-Derived R2 Peptides.(3) MUS:OT NPs Successfully Label Minute Amounts of Ex Vivo Samples and Allow Determination of Polymorph Distribution in HumanDerived Samples.