Probing Interfacial Charge Transfer between Amyloid-β and Graphene during Amyloid Fibrillization Using Raman Spectroscopy

Abstract

Charge transfer plays a key role in the structural transformation of amyloid-β proteins (Aβs), as it fibrillizes from small monomers to intermediate oligomers and to ordered fibrils. While the protein fibrillization states have been identified using cryo-electron microscopy, X-ray diffraction, Raman, infrared, terahertz spectroscopies, etc., there is little known about the electronic states during the fibrilization of Aβ protein. Here, we probe the charge transfer of Aβ42 proteins at different aggregation stages adsorbed on monolayer graphene (Gr) and molybdenum disulfide (MoS2) using Raman spectroscopy. Monomers, oligomers, and fibrils prepared in buffer solutions were deposited and dried separately on Gr and MoS2 where well-established characteristic Raman modes (G, 2D for Gr and E2g, A1g for MoS2) were monitored. The shifts in Raman parameters showed that the small Aβ monomers withdraw electrons, whereas fibrils donate electrons to Gr and MoS2. Oligomers undergo transient charge states near the neutrality point. This is explained in terms of modulated carrier concentration in Gr and MoS2. This finding provides insight into the electronic properties of Aβs that could be essential to identifying the onset of toxic fibril forms and developing a straightforward, label-free diagnosis using Gr and MoS2.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective

“…Although the surface contact of the organs to the 2D materials is likely very limited, we suggest the scientific community to carry out toxicity studies about the potential undesired effects on tissues beyond biomarker sensing. 483,484 In the present review, we have also discussed "green" chemistry approaches to minimize the environmental footprint of 2D materials. This aligns well with the "safe-and-sustainableby-design" (SSbD) concept that is embedded in the European Commission's Chemicals Strategy for Sustainability (CSS).…”

“…In certain cases, tissues from different organs might come into direct contact with the materials embedded into these devices. Although the surface contact of the organs to the 2D materials is likely very limited, we suggest the scientific community to carry out toxicity studies about the potential undesired effects on tissues beyond biomarker sensing. , …”

Current Trends of Raman Spectroscopy in Clinic Settings: Opportunities and Challenges

“…[ 118 ] Graphene‐assisted Raman spectroscopy has been applied to rapid biomarker screening for AD, where accurate detection and identification of specific biomarkers have been achieved by enhancing the Raman signals in samples. [ 119 ] Graphene has also been used to study the charge transfer process between amyloid β and graphene and the fibrillation process of amyloid β. [ 120,121 ] This study demonstrates the key role of graphene in probing protein interactions and molecular structural changes, providing detailed information for a deeper understanding of biomolecular properties.…”

Trapping Hydrogen Molecules between Perfect Graphene

“…We calculate the strain value dependence on the actual shape of the bubbles (Figure e). The strain of the bubble center here is considered to be the average strain, which strongly corresponds to the h max / R . , …”

“…The strain of the bubble center here is considered to be the average strain, which strongly corresponds to the h max /R. 22,42 We further characterize the bubbles with different heights from 25 to 244 nm by Raman spectra. When the diameter of the bubble is much smaller than the laser spot of Raman, we cannot detect the Raman characteristic peaks of the bubble domes, just like the bubble with 25 nm height, as shown in Figure 2f.…”