Sensitive fluorometric detection of alkaline phosphatase using a water-soluble conjugated polymer

Abstract

In this paper, we developed a new fluorescence method for highly sensitive and selective detection of the alkaline phosphatase (ALP) activity with phenyl phosphate (PP) as the enzyme substrate and water-soluble conjugated polymer PPESO3 as a fluorescent probe. Phenyl phosphate could be hydrolyzed to phenol via the ALP-catalyzed reaction. In the presence of horse radish peroxidase (HRP) and H2O2, phenol was rapidly oxidized to quinone which could efficiently quench the fluorescence of the conjugated polymer PPESO3. The fluorescence intensity change of PPESO3 is proportional to the concentration of ALP. Thus, we established a fluorescence method for ALP activity detection based on a water-soluble fluorescent conjugated polymer–enzyme hybrid system. Under the optimized conditions, a linear correlation was established between the fluorescence intensity ratio I/I0 (I0 and I were the fluorescence intensity of the sensing system in the absence and presence of ALP, respectively) and the concentration of ALP in the range of 0–30 U L−1, and the detection limit for ALP was 0.5 U L−1. The present method was applied to the determination of ALP in spiked human serum samples with satisfactory results.