Investigation of Nucleobase-Metal Complex-Based Nanozyme and the Application for Nitrite Detection

Nanozymes possess the features of high catalytic efficiency and stable physical and chemical properties, which are widely applied for building novel biosensing systems. We herein screen nucleobase-metal-complex-based nanozymes and develop a simplified method for nitrite detection. Four nucleobases are coupled with five common metal ions (Cu⁺, Cu²⁺, Fe³⁺, Zn²⁺, and Mn²⁺). Twenty nucleobase-metal complexes are thus synthesized as nanozyme candidates. By the evaluation of the TMB/H₂O₂ chromogenic system, adenine-copper (A-Cu²⁺) is found to exhibit excellent peroxidase-like activity, and the kinetic performance is well investigated. Thus, we select A-Cu²⁺ as the nanozyme and develop a ratiometric colorimetric biosensor for highly sensitive detection of nitrite. The utility in tap water, pickled cabbage, and sausage samples is well demonstrated. These findings not only indicate good catalytic efficiency of the screened A-Cu²⁺ but also provide a practical nitrite assay for the applications of food safety and environmental protection.