In-situ atomic force microscopy study of β-amyloid fibrillization

We report the use of atomic force microscopy to observe the initial stages of β-amyloid fibrillization in situ. The growth of individual β-amyloid protofibrils on a mica substrate was followed over several hours. The first in situ visualization of protofibril formation from single aggregate units of β-amyloid is reported. The growth of these protofibrils through the subsequent addition of these aggregate units is also observed. Growth of the protofibrils is bi-directional and the outgrowth of protofibrils from a common amyloid/heterogeneous core is also observed. Elongation also occurred by the addition of protofibrils from solution. This data provides an exciting insight into the early stages of β-amyloid fibrillization and can be used to enhance the understanding of the mechanism(s) by which β-amyloid fibrillizes and may consequently enable inhibition of one or more stages of fibrillization as a potential therapeutic strategy.