Noninvasive real-time monitoring of amyloid-βfibrillization via simultaneous label-free dielectric relaxation spectroscopy dark-field imaging

Accumulated evidence suggests that amyloid-βhas a critical role in chronic neurodegenerative disorders such as Alzheimer's disease. Therefore, understanding of amyloid-βfibrillization is a focus of interest for the Development of innovative therapeutic and diagnostic applications. The fibrillization of amyloidβhas similar growth characteristics of polymeric nanoparticles and current monitoring methods show only qualitative or static information. Here we describe a noninvasive real-time monitoring of nanoscale amyloidβfibrillization by simultaneous Dielectric Relaxation Spectroscopy (DRS) and label-free dark-field imaging. First, the hydrodynamic radius is characterized by DRS, which can reflect the averaged radius of fibrilized amyloidβ, and we observe an increase from 19 to 21 nm during 48 h. Scattering intensity from dark-field imaging allowed us to visualize and quantify the fibrillization with respect to the incubation time of amyloidβ. Consequently, real-time observation and quantification of changes in both hydrodynamic radii and optical properties (i.e., scattering intensity) were performed simultaneously. Such a dual-mode technique may prove valuable for elucidating the mechanism of amyloid fibrillization and ultimately for designing possible diagnostic methods.