Aβ42 fibril and non-fibril oligomers characterization using a nanopipette.

The Aβ42 aggregates with different structures and morphology was investigated through a single molecule label-free technique. To this end, the quartz nanopipettes were functionalized with polyethylene glycol. The set of Aβ42- epigallocatechin-3-gallate fibrils with length (from 85 nm to 250 nm) obtained by sonication was detected. The comparison of experimental and computed value of the amplitude of relative current blockade using a geometrical model show that for fibrils longer than 80 nm, the discriminating parameter is their diameter. Then, non-fibril oligomers obtain from Aβ42(Osaka) aggregation at different time seed was investigated. The analysis of the amplitude of relative current blockade shows that detected oligomers are smaller than 30 nm regardless the aggregation time. In addition, the wide distributions of the dwell time suggests the polymorph character of the sample.