Abstract
Plasmon-assisted effects were used in this work to study the dynamical behavior of amyloid β peptides (Aβ), in particular Aβ(25–35), on silver nanoparticles. Amyloid peptides derive from the proteolytic cleavage of the glycoprotein named amyloid precursor protein (APP). Aβ(25–35) represents the sequence that concentrates the biological active region of all of the amyloid peptide family, being the shortest fragment of Aβ that retains the toxicity of the full length. The plasmon effects employed in this work were the localized surface plasmon resonance (LSPR), the plasmon hybridization resulting from plasmonic NPs aggregation, and the enhancement of electric field leading to the so-called surface-enhanced Raman scattering (SERS) spectroscopy on nanostructures. While LSPR and plasmon hybridization of nanoparticles are highly sensitive to adsorption and dynamical processes undergone by these peptides on the metal surface, direct nonlabeled SERS spectra provided valuable information regarding the secondary structure of peptides. Specifically, SERS revealed the interaction mechanism of peptides with the metal and the structural rearrangement processes involved in the self-aggregation leading to fibrillation. These effects were also followed at different peptide concentrations. Plasmon resonance and SERS results were obtained with transmission electron microscopy (TEM) images that also corroborated the self-aggregation processes undergone by these peptides leading to the formation of supramolecular aggregates at different concentrations. Nanospheres and protofibrils formed in the first stages of the amyloid assembly were identified by TEM. The physicochemical information provided by this work will be of great importance to design plasmon-based nanoplatforms for simultaneous amyloid detection and structural characterization. Furthermore, these platforms have promising applications in the detection of Alzheimer’s disease and its treatment based on the bioaccumulation of these toxic peptides on NPs, where they can be trapped and removed from biological systems, thus reducing their neurotoxicity.
Highlights
The accumulation and aggregation of amyloid β peptides (Aβ) are considered as the beginning of all of the molecular and cellular effects that cause Alzheimer’s disease (AD) according to the amyloid hypothesis.[1]
This enhancement is of a shortrange character since the electric field on the NP surface varies with the distance to the metal surface in a nanosphere as
The dynamical behavior of Aβ(25−35) on AgNPs can be followed by changes in the localized surface plasmon resonance produced, either by LSPR shifts induced by peptide adsorption and self-assembly or by plasmon hybridization resulting from the NPs approaching and aggregation
Summary
The accumulation and aggregation of amyloid β peptides (Aβ) are considered as the beginning of all of the molecular and cellular effects that cause Alzheimer’s disease (AD) according to the amyloid hypothesis.[1]. Aβ peptides are produced after proteolytic cleavage of a larger glycoprotein named amyloid precursor protein (APP).[3] Among the APP cleavage degradation products, the amyloid β-peptides Aβ(1−42) and Aβ(1−40) (Figure 1) are the most studied, since they can form insoluble aggregates that have been shown to be associated with AD. In addition to these amyloids, other shorter related peptides can be found in AD plaques. This undecapeptide has been considered as the actual functional domain of Aβ peptides that concentrates the biological active region of all of the amyloid peptide family, representing the shortest fragment of Aβ retaining the toxicity of the fulllength peptide.[4−6] This particular peptide can be naturally produced in the organism, and under mono/oligomer forms, it Received: January 12, 2021 Accepted: March 30, 2021 Published: April 13, 2021
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