Noninvasive label-free nanoplasmonic optical imaging for real-time monitoring of in vitro amyloid fibrogenesis.

It is important to develop a noninvasive label-free detection method to monitor dynamic phenomena in biology and medicine. Here, we utilize nanoplasmonic optical imaging as the noninvasive and label-free method in order to monitor in vitro amyloid fibrogenesis in real-time, which is considered as the primary pathological mechanism of Alzheimer's disease. Using Rayleigh scattering of gold nanoplasmonic probes (GNPs), which have an enhanced scattering optical cross-section due to the surface plasmon resonance, we accomplished efficient tracking of the random movements of the GNPs in Aβ solution, and quantified the kinetics of the fibrogenesis. We expect that this noninvasive and label-free in vitro method can be utilized in monitoring in a wide range of other research fields as well. As future applications, we can envision long-term monitoring in neuronal cells to elucidate the mechanism of amyloid growth and NIR-based in vivo imaging with nanoplasmonic optical antennas for gene delivery, photonic gene circuits, and monitoring toward the theranostics of neurodegenerative diseases.