Bioinspired Popcorn‐Like Nitrogen‐Doped Nickel Sulphide as Superoxide Dismutase Mimicking Nanozyme Toward Selective Electrochemical Detection of Superoxide Anions

Superoxide anion radicals (O₂ ^•-) belong to the family of reactive oxygen species, which act as a biomarker and regulate vital physiological and pathological functions. Any deviation in its concentration is known to cause several detrimental diseases and therefore, detection of O₂ ^•- is crucial for health screening and early disease diagnosis. Electrochemical biosensors for O₂ ^•- sensing using superoxide dismutase (SOD) enzyme tend to denature under harsh physiological conditions, thereby limiting their real-time application. To date, nanozymes are in the spotlight owing to their ability to overcome the drawbacks faced by traditional enzymes. Accordingly, judicious design of nanozymes that could mimic natural SOD enzyme, and employing it toward the detection of O₂ ^•- is of great significance. Herein, we have synthesized popcorn-like, nitrogen-doped nickel sulphide microspheres as a nickel-superoxide dismutase mimetic, and employed it toward electrochemical detection of O₂ ^•-. The fabricated nanozyme sensor portrayed remarkable sensing toward O₂ ^•- with a linear range of 20 µM to 1.2 mM and a detection limit of 5.31 µM. The sensor was also employed toward real-time detection of O₂ ^•- in human serum samples, where it showed good recovery rates, and further established excellent operational and long-term stability.