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Updated: Oct 7, 2025
Characterizing Individual Protein Aggregates by Infrared Nanospectroscopy and Atomic Force Microscopy
Published on: September 12, 2019
In Situ Monitoring the Aggregation Dynamics of Amyloid-β Protein Aβ42 in Physiological Media via a Raman-Based
Wenfeng Zhu1,2, Yibing Wang3, Dan Xie1
1CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Shijingshan District, Beijing 100049, China.
Abstract:
Amyloid-β protein (Aβ) is a major biomarker candidate for the diagnosis of Alzheimer's disease (AD). It is known that the core segment of Aβ42 tends to aggregate into neurotoxic soluble oligomeric species and finally into fibrillar structures associated with AD; however, much remains to be learned about the conformational changes and dynamic aggregation processes of Aβ protein in solution. Herein we exploit the selectivity of affinity peptides, singled out by biopanning a phage display library, to recognize and capture Aβ42 and its fibers. The sensitivity of surface-enhanced Raman spectroscopy (SERS) to subtle electronic changes of a Raman reporter upon Aβ42 binding, that is, the frequency shift SERS assay, is employed to develop a reliable sensor for both in situ Aβ42 aggregation monitoring and Aβ42 monomers and fibers detection. Atomic force microscope (AFM) imaging is used to investigate the dynamic aggregation processes of Aβ42 on mica and confirms the conclusions of the SERS studies. Finally sensing of Aβ42 and its fibers in fetal bovine serum (FBS) solution is shown to have a limit of detection of ∼10-9 mol/L.
Insights
Researchers developed a new sensor to detect amyloid-beta protein (Aβ) and its aggregation, crucial for Alzheimer's disease (AD) diagnosis. This method uses affinity peptides and SERS for sensitive detection of Aβ42 monomers and fibers.
Area of Science:
- Biochemistry
- Neuroscience
- Biomaterials
Background:
- Amyloid-beta protein (Aβ) aggregation, particularly Aβ42, is central to Alzheimer's disease (AD) pathogenesis.
- Understanding the dynamic aggregation processes and conformational changes of Aβ in solution is critical for developing diagnostic and therapeutic strategies.
- Current methods for detecting Aβ species and monitoring aggregation require further refinement for sensitivity and in situ analysis.
Purpose of the Study:
- To develop a novel sensor for the detection and in situ monitoring of amyloid-beta protein (Aβ) aggregation.
- To utilize affinity peptides and surface-enhanced Raman spectroscopy (SERS) for sensitive and selective recognition of Aβ42 monomers and fibers.
- To investigate the dynamic aggregation processes of Aβ42 using complementary techniques.
Main Methods:
- Phage display biopanning to select affinity peptides that recognize Aβ42 and its fibers.
- Frequency shift SERS assay to detect subtle electronic changes upon Aβ42 binding.
- Atomic force microscope (AFM) imaging to visualize Aβ42 aggregation dynamics on mica surfaces.
Main Results:
- Successfully identified affinity peptides capable of capturing Aβ42 and its aggregated forms.
- Developed a sensitive SERS-based sensor demonstrating frequency shifts upon Aβ42 binding.
- AFM imaging corroborated SERS findings, providing insights into Aβ42 aggregation pathways.
- Achieved a limit of detection of approximately 10-9 mol/L for Aβ42 and its fibers in fetal bovine serum.
Conclusions:
- The developed affinity peptide-SERS sensor provides a reliable platform for in situ monitoring of Aβ42 aggregation.
- The sensor enables sensitive detection of both Aβ42 monomers and fibers, offering potential for early Alzheimer's disease diagnosis.
- Combined SERS and AFM approaches offer a comprehensive understanding of Aβ42 aggregation dynamics.
