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Evaluation of Redox Peptide Modified Surfaces for Biosensing Applications
* 1 , 2 , 1 , 2 , 1
1  Department of Biochemistry and Organic Chemistry, Institute of Chemistry, UNESP - Univ Estadual Paulista, São Paulo, Brazil
2  Department of Physical Chemistry, Nanobionics Research Group, Institute of Chemistry, UNESP - Univ Estadual Paulista, São Paulo, Brazil (registering DOI)

Peptides are promising tools for designing sensitive and stable biosensors. For example, the redox self-assembled monolayer (SAM) based on the sequence Fc-Glu-(Ala)2-Cys-NH2 was successful evaluated as transducing interface in electrochemical biosensors. The design of such peptides includes: 1) cysteine to bind covalently the peptide to the gold electrode; 2) glutamic acid in N-terminal position to bind the ferrocene (Fc) in the amine group, and the antibody in the δ-carboxyl group, and 3) alanine to form a hydrophobic layer. Herein, we present the solid-phase synthesis of three different peptides with structure Fc-Glu-(X)2-Cys-NH2 (X=Ser, Gly or Phe) and the electrochemical behavior of the obtained SAMs. The Gly was chosen because of its smallest side chain, while Ser and Phe present hydroxyl groups (for H-bonds) and aromatic (for π-π interaction), respectively. The synthesis successful of the HPLC purified peptides were confirmed by mass spectroscopy. From cyclic voltammetry and impedance-derived electrochemical capacitance spectroscopy results, all peptides present reversible redox processes, and electron transfer rates (kET ) ranging from 17 to 31 s-1. Since the peptide with Gly residues presented both the highest surface coverage (Γ = 2.6x10-10 mol/cm2) and electrochemical capacitance (Cµ = 270 µF/cm2) values, it can be potentially applied for biosensors designing.

Keywords: Self-assembled monolayer; Biosensor; Ferrocene-tagged Peptide; Electroactive peptide