A peptide nucleic acid (PNA)-DNA ferrocenyl intercalator for electrochemical sensing

A ferrocenyl intercalator was investigated to develop an electrochemical DNA biosensor employing a peptide nucleic acid (PNA) sequence as capture probe. After hybridization with single strand DNA sequence, a naphthalene diimide intercalator bearing ferrocene moieties (FND) was introduced to bind with the PNA-DNA duplex and the electrochemical signal of the ferrocene molecules was used to monitor the DNA recognition.
Electrochemical impedance spectroscopy was used to characterize the different modification steps. Differential pulse voltammetry was employed to evaluate the electrochemical signal of the FND intercalator related to its interaction with the complementary PNA-DNA hybrid. The ferrocene oxidation peaks were utilised for the target DNA quantification.
The developed biosensor demonstrated a good linear dependence of FND oxidation peak on DNA concentration in the range 1 fM to 100 nM of target DNA, with a low detection limit of 11.68 fM. Selectivity tests were also investigated with a non-complementary DNA sequence, indicating that the FND intercalator exhibits a selective response to the target PNA-DNA duplex.