Fabrication of an electrochemical immunosensor with self-assembled peptide nanotubes

Fabrication and notably improved performance of composite electrodes based on the peptide nanotubes is described. Peptide nanotubes were constructed by self-assembly of cyclic peptides consisted of alternated d- and l-amino acid residues. The self-assembled peptide nanotubes were deposited onto the screen-printed carbon paste electrode prepared by a sol–gel method. The antibodies against Escherichia coli O157:H7 were reacted by themselves onto the peptide nanotubes. The binding of peptide nanotubes and antibodies was confirmed by fluorescence microscopy. The E. coli O157:H7 cells were attached onto the antibody-modified electrode using the antigen-antibody interaction. Direct measurement with cyclic voltammetry (CV) in the presence of [Fe(CN)6]3−/4− as a redox probe showed that the immobilization of antibodies and the binding of E. coli cells to the peptide nanotube modified electrode increased the electron-transfer resistance.