Highly Active Oxidase-like N-Mn₃O₄ Nanoparticles from Amino Acid Nitrogen Source for Dual-Mode Detection of Acid Phosphatase

Defect-engineered nanomaterials have been found to improve catalytic activity, making them highly desirable for biosensor preparation. Nitrogen doping is an effective method for introducing defects in nanomaterials, and amino acids containing nitrogen atoms can be used as a nitrogen source for doping nanozymes. In this study, nitrogen-doped N-Mn 3 O 4 nanoparticles (NPs) were synthesized using various amino acids as nitrogen sources. The results indicate that N-Mn 3 O 4 NPs doped with histidine as a nitrogen source exhibit the highest oxidase-like activity. Additionally, N-Mn 3 O 4 NPs have a V max that is 5.4-fold higher and a K m that is 1/2-fold lower than Mn 3 O 4, suggesting that histidine-doped N-Mn 3 O 4 NPs can be used to create highly active oxidase-like enzymes. A dual-modal sensor utilizing both ratiometric fluorescence and smartphone-based colorimetry method with a smartphone has been developed for the detection of acid phosphatase, based on N-Mn 3 O 4 NPs with high enzymatic activity. This study presents an approach to constructing highly active oxidase-like and realizing a highly sensitive assay for detecting acid phosphatase with high interference resistance. The mechanisms underlying the improved performance of nitrogen-doped nanomaterials and their potential applications in biosensor fields were also discussed.