Affiliations: [a] Forschungszentrum Jülich, ICS-6, Institut für Strukturbiochemie, Jülich, Germany | [b] Forschungszentrum Jülich, ZEA-3, Zentralinstitut für Engineering, Elektronik und Analytik, Jülich, Germany | [c] Heinrich-Heine-Universität Düsseldorf, Institut für Physikalische Biologie, Düsseldorf, Germany
Correspondence:
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Correspondence to: Prof. Dr. Dieter Willbold, ICS-6, Institut für Strukturbiochemie, Forschungszentrum Jülich, 52428 Jülich, Germany. Tel.: +49 2461 61 2100; Fax: +49 2461 61 2023; E-mail: d.willbold@fz-juelich.de.
Note: [1] Current address: Albert Einstein College of Medicine, Institute of Anatomy and Structural Biology, Laboratory of Molecular and Cellular Biophysics, New York City, USA.
Abstract: Amyloid-β (Aβ) oligomers represent a promising biomarker for the early diagnosis of Alzheimer’s disease (AD). However, state-of-the-art methods for immunodetection of Aβ oligomers in body fluids show a large variability and lack a reliable and stable standard that enables the reproducible quantitation of Aβ oligomers. At present, the only available standard applied in these assays is based on a random aggregation process of synthetic Aβ and has neither a defined size nor a known number of epitopes. In this report, we generated a highly stable standard in the size range of native Aβ oligomers that exposes a defined number of epitopes. The standard consists of a silica nanoparticle (SiNaP), which is functionalized with Aβ peptides on its surface (Aβ-SiNaP). The different steps of Aβ-SiNaP synthesis were followed by microscopic, spectroscopic and biochemical analyses. To investigate the performance of Aβ-SiNaPs as an appropriate standard in Aβ oligomer immunodetection, Aβ-SiNaPs were diluted in cerebrospinal fluid and quantified down to a concentration of 10 fM in the sFIDA (surface-based fluorescence intensity distribution analysis) assay. This detection limit corresponds to an Aβ concentration of 1.9 ng l–1 and lies in the sensitivity range of currently applied diagnostic tools based on Aβ oligomer quantitation. Thus, we developed a highly stable and well-characterized standard for the application in Aβ oligomer immunodetection assays that finally allows the reproducible quantitation of Aβ oligomers down to single molecule level and provides a fundamental improvement for the worldwide standardization process of diagnostic methods in AD research.
