Electrochemical Response of α/β-peptides: Influence of the Peptide Length, Stereochemistry and Self-Assembly on the Performance of Peptide-Based Electrochemical Sensors

The electrochemical response of α/β-peptides with (L-Ala-β-Fpg)_n sequence, where β-Fpg refers to syn 3-amino-2-(2-fluorophenyl)-3-phenylpropanoic acid, has been investigated examining the effects of the peptide length (n = 1–3), the stereochemistry of the β^2,3-diaryl-amino acid and their self-assembly. α/β-Peptides have been deposited by drop-casting on a conducting polymer (CP) film, which is previously electropolymerized on a stainless steel conducting substrate. The current-potential response of the CP coated by the different studied peptides suggests that, for α/β-peptides, the role played by the electron transport through intermolecular stacking of aromatic side groups prevails over peptide length and stereochemistry. In order to prove such a hypothesis, the experimental conditions used to achieve an ordered self-assembly are optimized for one of the α/β-peptides. The achieved self-assembled structures, which consist of well-defined long microfibers, considerably improve the electrochemical response of the CP. Finally, the prepared α/β-peptide-based electrodes are used to electrochemically detect the oxidation of nicotinamide adenine dinucleotide (NADH). The analytical parameters are better for electrodes with well-defined peptide microfibers than for uncoated CP, corroborating the importance of π-π stacking interactions in the response of α/β-peptides.