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

Considering the critical roles of superoxide anion (O2∙−) in pathological conditions, it is of great urgency to establish a reliable and durable approach for real-time determination of O2∙−. In this study, we propose a porous Pt-Pd decorated superoxide dismutase (SOD) sensor for qualitative and quantitative detection O2∙−. The developed biosensor exhibits a fast, selective and linear amperometric response upon O2∙− in the concentration scope of 16 to 1536 μM (R2=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 O2∙−. 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 O2∙− 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 O2∙− 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 O2∙−in vivo.