An electrochemical biosensor based on electroactive peptide nanoprobes for the sensitive analysis of tumor cells

Peptides possess many appealing and desirable features, which have attracted increasing attention in the field of electrochemical biosensing. However, peptides hardly produce noticeable electronic signals in response to target binding events. In this work, amphipathic peptides FFFGGGGRGDS with both target recognition and self-assembly capabilities are designed to be co-assembled with the electroactive species ferrocenecarboxylic acid (FcCOOH). Furthermore, the resultant electroactive peptide nanoprobes (ePNPs) are applied for sensitive electrochemical analysis of tumor cells. Specifically, tumor cells are captured by the electrode modified with the corresponding DNA aptamers, and ePNPs can then selectively bind to integrin proteins on the cell surface, thereby accompanied by a remarkable increase of electrochemical signal. Taking the assay of MDA-MB-231 cells, the fabricated biosensor can detect cancer cells with a detection limit of 7 cells mL^-1. Moreover, the ePNPs can act as a universal probe for the detection of different cell lines. Given the merits of easy synthesis, convenient operation, and favorable analytical performance, the proposed biosensor exhibits great potential in developing peptide-based electrochemical biosensing for clinical applications.