Immobilization of superoxide dismutase on Pt–Pd/MWCNTs hybrid modified electrode surface for superoxide anion detection

Monitoring of reactive oxygen species like superoxide anion (O 2 ∙− ) turns to be of increasing significance considering their potential damages to organism. In the present work, we fabricated a novel O 2 ∙− electrochemical sensor through immobilizing superoxide dismutase (SOD) onto a Pt–Pd/MWCNTs hybrid modified electrode surface . The Pt–Pd/MWCNTs hybrid was synthesized via a facile one-step alcohol-reduction process, and well characterized by transmission electron microscopy , X-ray photoelectron spectroscopy and X-ray diffraction. The immobilization of SOD was accomplished using a simple drop-casting method, and the performance of the assembled enzyme-based sensor for O 2 ∙− detection was systematically investigated by several electrochemcial techniques. Thanks to the specific biocatalysis of SOD towards O 2 ∙− and the Pt–Pd/MWCNTs – promoted fast electron transfer at the fabricated interface, the developed biosensor exhibits a fast, selective and linear amperometric response upon O 2 ∙− in the concentration scope of 40–1550   μM ( R 2 =0.9941), with a sensitivity of 0.601   mA   cm −2   mM −1 and a detection limit of 0.71   μM ( S / N =3). In addition, the favorable biocompatibility of this electrode interface endows the prepared biosensor with excellent long-term stability (a sensitivity loss of only 3% over a period of 30 days). It is promising that the proposed sensor will be utilized as an effective tool to quantitatively monitor the dynamic changes of O 2 ∙− in biological systems.