Nanozyme-Based Detection of Alkaline Phosphatase

Herein, a colorimetric detection strategy for alkaline phosphatase (ALP) activity was established based on an Fe-doped carbon-based nanozyme. By doping Fe into a Zn MOF and introducing dicyandiamide for pyrolysis, we obtained a two-dimensional carbon nanosheet with exceptional peroxidase-mimicking activity (Fe/C NS). The Fe/C NS has superior affinity to H2O2, can decompose H2O2 into reactive oxygen species, and further oxidize reducing substances such as phenol. ALP can hydrolyze disodium phenyl phosphate into phenol, while the Fe/C NS can promote the reaction between phenol and 4-aminoantipyrine in the presence of H2O2 to produce red quinone imine. Based on the changes of absorbance of the reaction system, ALP activity can be detected in a range of 0.05–6.00 U·L–1 with a detection limit of 0.03 U·L–1. Furthermore, we developed a quantitative relationship between ALP activity and color characteristic values by recording the RGB (red, green, and blue) values of color changes under different ALP concentrations, realizing the convenient determination of ALP activity without specific analytical equipment. This work can effectively broaden the application of nanozymes in biological analysis.