Electrochemical “Signal‐On” Reporter for Amyloid Aggregates

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 Aβ(12-28) fragments were studied by circular dichroism (CD), transmission electron microscopy (TEM), and electrochemistry. All four Fc-peptides interacted favourable with Aβ(12-28) 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 Aβ(12-28)/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 Aβ(12-28)-Cys films on Au surfaces were detected by measuring the current response of the Fc redox process. The formal redox potential, E(0), at ~440 (10) mV and i(pc)/i(pa) 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 Aβ(12-28)-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 Aβ(12-28)-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 Aβ(12-28).

Electrochemical Methods for the Analysis of Clinically Relevant Biomolecules

“…A signal-ON voltammetric sensor for Aβ (12−28) was fabricated using Aβ (12−28) -Cys immobilized onto the surface of a gold electrode. 927 Ferrocene bioconjugates, bearing a podant (Lys)-Leu-Val-Phe-Phe motif, interacted with the immobilized Aβ (12−28) -Cys film on the gold surface followed by measuring the current response of the ferrocene redox process.…”

Electrochemistry of Nonconjugated Proteins and Glycoproteins. Toward Sensors for Biomedicine and Glycomics

“…The EC response enabled monitoring the kinase activity and its substrate, as well as the effect of small molecule inhibitors on protein phosphorylation. The authors developed peptide biosensors, for example, for papain, protein kinase C, serine/threonine kinase, sarcoma-related kinase, , HIV enzymes, , STAT3 dimerization, or even amyloid β peptides . More recently, this strategy was extended to an immunoarray format, in which authors utilized anti-Fc antibodies for visualization of the protein kinase-driven transfer of the phosphate group from Fc-ATP to the hydroxyl group of peptides or proteins …”

Electroanalytical Sensors and Methods for Assays and Studies of Neurological Biomarkers

“…For example, Kraatz and coworkers synthesized several Fc‐tagged peptides containing the hydrophobic sequence (LVFF) of Aβ. These Fc‐tagged peptides were allowed to interact with immobilized Aβ(12–28) films at Au electrodes and subsequently detected by measuring the current response of the Fc tag 38. Our group recently reported the synthesis of a water‐soluble ferrocene(Fc)‐tagged β‐sheet breaker peptide, Fc‐KLVFFK 6 and its application as an electrochemical probe for kinetic studies of the inhibition of the Aβ(1–42) fibrillation process.…”