Adsorption of β-amyloid oligomers on octadecanethiol monolayers

Abstract

Hypothesis: β-Amyloid oligomers of different aggregation and physiological functions exhibit distinct adsorption behavior allowing them to be discriminated in preparations.

Experiments: Two forms of amyloid oligomers, small 1-4 nm and large 5-10nm were formulated using synthetic 42 amino acids β-amyloid peptide. Forms differ in their size and physiological function. A systematic study of adsorption of these amyloid species on self-assembled monolayers of octadecanethiol on gold was performed. Structural changes upon adsorption of oligomers were interrogated by the reflection absorption infrared spectroscopy.

Findings: The amount of adsorbed peptide material, as detected by surface plasmon resonance spectroscopy, is similar in case of both small and large oligomers. However, adsorption of small oligomers leads to a transformation from beta sheet rich to beta sheet depleted secondary structure. These changes were accompanied by the unique morphology patterns detectable by atomic force microscopy (AFM), while the quartz microbalance with dissipation indicated a formation of a compact adsorbate layer in case of small oligomers. These effects may be integrated and utilized in bioanalytical systems for sensing and detection of Alzheimer's disease related peptide forms in artificial, and possibly, real preparations.

Keywords: Adsorption; Alzheimer’s; Amyloid; Atomic force microscopy; Hydrophobic surfaces; Oligomers; Quartz microbalance; RAIRS; Self-assembled; Surface plasmon resonance spectroscopy.