Investigations of poly(p-phenylene) modified with ferrocene and their application in electrochemical DNA sensing

Abstract Hybrid polymer based on poly(p-phenylene) PPP modified with ferrocene groups, as side chains, has been synthesized. The optical study, investigated in solution by UV–visible spectroscopy, has revealed a band gap of 3 eV which is lower than the same structure of modified PPP without ferrocene as pendant group. The electrochemical properties of the formed polymer membrane were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The kinetic analysis of such polymers demonstrated a rate of electron transfer of 68 s −1 . The results show that the polymer has both electronic and ionic conductivity due to the electronic structure of such materials where the polymer PPP is attached to ferrocenyl group through unsaturated side chain. Membranes based on this polymer deposit on surface, were used as electrochemical transducer for DNA sensing. The chemical modification of the polymer backbone has been performed by innovative approach where the electrodeposition of β-alanine though amine oxidation and their covalent attachment on poly(p-phenylene) has been demonstrated through FT-IR and XPS measurement. DNA attachment was then realized through the reaction of their terminal amine group on 5′ position following EDC/NHS chemistry. The biolayer properties through DNA sensing of hepatitis C as model were followed by redox signal of the polymer layer. We demonstrated that hybridization reaction of DNA on the polymer (Fc-PPP) surface leads to a variation of the redox properties of the attached ferrocene on side group of PPP. High sensitivity with a limit of detection (LOD) of 30 fM and wide linear range of detection from 1 fM to 10 pM has been demonstrated. Through this study we demonstrate that Fc-PPP present high potential as electrochemical transducer to follow the molecular recognition of biological reaction such as DNA hybridization.