Combination of hematin and PEDOT via 1-pyrenebutanoic acid: A new platform for direct electrochemistry of hematin and biosensing applications

In this work, we prepare a novel platform based on poly(3,4-ethylenedioxythiophene) (PEDOT) and 1-pyrenebutanoic acid (PBA). PEDOT is a conductive material of heteroatom doping, which can connect with PBA through π-π stacking. The feasibility of the film is verified via fabricating it on a glassy carbon electrode (GCE); then, hematin is linked with PBA via carboxylate-zirconium-carboxylate coordination bond to prepare a GCE/PEDOT-PBA-hematin biosensor. The electrochemical performance of the biosensor has been tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and current-time curve method (I-T). From CV, a pair of well-defined and quasi-reversible redox peaks, corresponding to the hematin Fe(iii)/Fe(ii) redox couple, is observed, and the surface coverage (Γ∗) of hematin on GCE has been calculated to be 1.2 × 10^-9 mol cm^-2, which is almost 20 times larger than the monolayer coverage of hemin. This value shows that the PEDOT and PBA composite results in a better loading of hematin on the surface of the GCE. In addition, the GCE/PEDOT-PBA-hematin biosensor exhibits strong electro-catalysis activity for H₂O₂ and displays a linear response for the reduction of H₂O₂ in the range of 0.005 to 1.322 mmol L^-1 with a detection limit of 0.03 μmol L^-1 and a high sensitivity of 2.83 μA mM^-1 cm^-2. In addition, the sensor has been applied to the determination of H₂O₂ in real samples, and the response is in the ideal range, which implies that the GCE/PEDOT-PBA-hematin biosensor has promising future applications.