Electrochemical “Signal-On” Reporter for Amyloid Aggregates

Authors

  • Samaneh Beheshti,

    1. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1 A4 (Canada)
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  • Dr. Sanela Martić,

    1. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1 A4 (Canada)
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  • Prof. Heinz-Bernhard Kraatz

    Corresponding author
    1. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1 A4 (Canada)
    • Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1 A4 (Canada)
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Abstract

The synthesis and characterization of four new Ferrocene (Fc) bioconjugates, bearing a podant (Lys)-Leu-Val-Phe-Phe motif, namely the hydrophobic sequence of amyloid-β-peptides (Aβ), is reported. The Fc-peptide conjugates are characterized by a reversible redox activity and the ability to undergo hydrophobic and hydrogen bonding interactions. Biomolecular interactions between Fc-bioconjugates with Aβ12–28 fragments were studied by circular dichroism (CD), transmission electron microscopy (TEM), and electrochemistry. All four Fc-peptides interacted favourable with Aβ12–28 and prevented fibril formation, the extent of which depended on the length of the peptide and the nature of the C-terminal group. The aggregates obtained for the Aβ12–28/Fc-peptide mixtures range from short fibrils to spherical aggregates. We demonstrated that in solution the peptide sequence and peptide charge affect the biomolecular interactions. Fc-peptide interactions with immobilized Aβ12–28-Cys films on Au surfaces were detected by measuring the current response of the Fc redox process. The formal redox potential, E0, at ∼440 (10) mV and ipc/ipa at 0.9 were observed characteristic for the monosubstituted Fc-derivative undergoing a one-electron redox process. On the surface, methyl ester-protected Fc-peptides (1 and 3) interacted only weakly with Aβ12–28-Cys films, giving rise to minimal redox activity. In contrast, charged Fc-peptides (2 and 4) gave a significant electrochemical readout following the interaction with Aβ12−28-Cys films. Interestingly, the Fc-peptide charge dictates the surface-assisted interactions, while hydrophobic and ionic effects contribute to the overall solution behaviour of the Fc-bioconjugates with Aβ12–28.

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