Ultrasensitive Detection of Aß42 Seeds in Cerebrospinal Fluid with a Nanopipette-Based Real-Time Fast Amyloid Seeding and Translocation Assay.

In this work, early-stage Aß42 aggregates were detected using a real-time fast amyloid seeding and translocation (RT-FAST) assay. Specifically, Aß42 monomers were incubated in buffer solution with and without preformed Aß42 seeds in a quartz nanopipette coated with L-DOPA. Then, formed Aß42 aggregates were analyzed on flyby resistive pulse sensing at various incubation time points. Aß42 aggregates were detected only in the sample with Aß42 seeds after 180 min of incubation, giving an on/off readout of the presence of preformed seeds. Moreover, this RT-FAST assay could detect preformed seeds spiked in 4% cerebrospinal fluid/buffer solution. However, in this condition, the time to detect the first aggregates was increased. Analysis of Cy3-labeled Aß42 monomer adsorption on a quartz substrate after L-DOPA coating by confocal fluorescence spectroscopy and molecular dynamics simulation showed the huge influence of Aß42 adsorption on the aggregation process.