A fluorescent assay for alkaline phosphatase activity based on phosphorylation protection and DNAzyme-assisted amplification

[Display omitted] •A fluorescent ALP detective method with considerable LOD of 0.0017 U L−1 and wide linear range of 0.0025–250 U L−1.•DNAzyme catalyzed cleavage and exo I mediated degradation were combined to extensively enhance the signal.•This method was applicable for analysis of cell lyses and inhibitor screening. Alkaline phosphatase is one of the most important tool enzymes and diseases indicator, monitoring ALP activity with convenient, precise, efficient and sensitive methods plays a fundamental role in modern life and healthcare industries. In this study, we described a novel method for ALP analysis based on Pb2+ dependent DNAzyme. By modifying DNAzyme sequence with terminal phosphate group and introducing exonuclease I (exo I), we managed to analyze ALP by utilizing its causal function of DNAzyme probe from exo I mediated degradation and function of triggering the subsequent cleavage of the hairpin reporting probe. Other than one amplificative strategy by DNAzyme mediated cleavage and cycle, this system also involved an exo I mediated degradation to further reduce the background noise. Combining stepwise fluorimetry and electrophoresis, we verified the detective mechanism of this proposed method. Further, after selectivity demonstration, this method achieved a considerable LOD of 0.0017 U L−1 and linear range of 0.0025 U L−1 to 250 U L−1. For potential of practical application, this method also exhibited excellent performances in inhibitor screening and intracellular ALP assay, both with a linear fitting equation. Based on these results, this method should be highly committed for improving ALP analysis in modern life industry.