Tip-enhanced Raman spectroscopy of Aβ(1-42) fibrils

Highlights: • Tip-enhanced Raman spectroscopy (TERS) imaging is performed on Aβ(1-42) fibrils. • The TERS lateral spatial optical resolution is ~ 16 nm. • Aromatic amino acid residues, β-sheet and random coil secondary structures can be identified. • TERS measurements prove that the surface and the core of fibrils are probed. • Several β-sheet and disordered fibril regions with different hydrophilicity are evidenced. Using tip-enhanced Raman spectroscopy (TERS) imaging with a lateral optical resolution of ~16 nm, the heterogeneity of Aβ(1-42) fibrils implicated in Alzheimer's disease is investigated. The amount and spatial distribution of TERS bands assigned to aromatic amino acid residues (histidine, tyrosine and phenylalanine) and to parallel β-sheet and random coil secondary structures suggest that both the surface and core of Aβ(1-42) fibrils are probed, confirm the twisted nature of the fibrils and reveal the presence of several β-sheet and disordered fibril regions with different hydrophilicity. This study completes and bears out literature TERS data on Aβ(1-42) amyloid fibrils.