Ultrasensitive detection of superoxide anion released from living cells using a porous Pt–Pd decorated enzymatic sensor

Considering the critical roles of superoxide anion (O 2 ∙− ) in pathological conditions, it is of great urgency to establish a reliable and durable approach for real-time determination of O 2 ∙− . In this study, we propose a porous Pt–Pd decorated superoxide dismutase (SOD) sensor for qualitative and quantitative detection O 2 ∙− . The developed biosensor exhibits a fast, selective and linear amperometric response upon O 2 ∙− in the concentration scope of 16 to 1536   μM ( R 2 =0.9941), with a detection limit of 0.13   μM (S/N=3) and a low Michaelis–Menten constant of 1.37   μM which indicating a high enzymatic activity and affinity to O 2 ∙− . Inspiringly, the proposed sensor possesses an ultrahigh sensitivity of 1270   μA   mM −1   cm −2 . In addition, SOD/porous Pt–Pd sensor exhibits excellent anti-interference property, reproducibility and long-term storage stability. Beyond our expectation, the trace level of O 2 ∙− released from living cells has also been successfully captured. These satisfactory results are mainly ascribed to (1) the porous interface with larger surface area and more active sites to provide a biocompatible environment for SOD (2) the specific biocatalysis of SOD towards O 2 ∙− and (3) porous Pt–Pd nanomaterials fastening the electron transfer . The superior electrochemical performance makes SOD/porous Pt–Pd sensor a promising candidate for monitoring the dynamic changes of O 2 ∙− in vivo .