Preparation of fluorescent polydopamine nanoparticles regulated by CoOOH nanosheets for detection of alkaline phosphatase activity

Abstract

Alkaline phosphatase (ALP) is an important enzyme which is widely distributed in organisms and participate in the vital process of dephosphorylation, often serve as a common biomarker for clinical diagnosis and treatment of human diseases. Herein, we reported a novel and simple strategy for the preparation of polydopamine nanoparticles (PDANPs) by employing CoOOH nanosheets as an oxidant. In the presence of CoOOH nanosheets, dopamine is easy to be oxidized and self-polymerize into fluorescent PDANPs. By employing the synthesized PDANPs as an effective fluorescence indicator, a fluorescence biosensor was established for label-free and sensitive determination of ALP activity based on the redox reaction between CoOOH nanosheets and the ALP hydrolysis product ascorbic acid (AA), and the dependence of CoOOH nanosheets concentration for formation of PDANPs. In the presence of ALP, the substrate ascorbic acid 2-phosphate (Asc-2P) was catalytically hydrolyzed and released free ascorbic acid, which could in situ reduction of Co(III) of CoOOH to Co(II) ions, resulting in the suppression of oxidation ability of CoOOH nanosheets, thus preventing the synthesis of fluorescent PDA. Therefore, the activity of ALP can be feasibly detected according to the changes of fluorescence peak at 490 nm of PDANPs. The sensor displays a linear range from 0.5 U/L to 300 U/L with a detection limit of 0.1 U/L. Moreover, the developed strategy exhibits good selectivity over other potential interference existing in human serum sample. The synthesis process of fluorescence PDANPs was facile and cost-effective, the proposed convenient and label-free fluorescence PDANPs detection platform shows potential applications in clinical diagnosis and provides a new paradigm for biological analysis.