Oligomer sensitive in-situ detection and characterization of gold colloid aggregate formations observed within the hippocampus of the Alzheimer's disease rat.

In order to better understand the dynamics governing the formation of pathological oligomers leading to Alzheimer's disease (AD) in a rat model the present study examined the protein aggregates accumulating on gold colloids in the hippocampus. Sections of the hippocampus of the Long Evans Cohen's AD(+) rat model were mixed with gold colloids and the resulting aggregates were examined by Surface Enhanced Raman Scattering (SERS) imaging. Compared to AD(-) rat tissues, the AD(+) rat hippocampal tissues produced a larger sized gold colloid aggregates. The SERS spectrum of each hippocampal section exhibited similar spectral patterns in the Amide I, II, and III band regions, but showed distinct spectral patterns in the region between 300 cm - 1250 cm in AD(+) rat tissues, respectively. Amyloid fibrils with a β-sheet conformation were previously reported to form gold colloid aggregates in mouse and human AD brain tissues. The gold colloid aggregates in the AD (+) rat hippocampal brain sections showed distinct morphological traits compared to those observed in AD(-) rats. This suggests that there is a spatial distribution of oligomer concentration in the hippocampus, which induces fibril formation to disrupt neuronal networks within the hippocampus and between other parts of the brain.