Fluorescent and colorimetric dual-mode assay of alkaline phosphatase activity via destroying oxidase-like CoOOH nanoflakes $(document).ready(function() { if (!$("html").hasClass("ie8")) { $.ajax({ url: "https://crossmark-cdn.crossref.org/widget/v2.0/widget.js", dataType: "script", cache: true }).done(function() { $(".crossmark-button").addClass("visible"); }); } });

Abstract

Nanozymes are increasingly exploited as components in bioanalysis and diagnostics. Here, we report a fluorescent and colorimetric dual-mode assay for alkaline phosphatase (ALP) activity employing oxidase-like cobalt oxyhydroxide (CoOOH) nanoflakes. Colorless o-phenylenediamine (OPD), a substrate for oxidase, can be oxidized to a product (OxOPD) with yellow color and orange fluorescence in CoOOH nanoflake solution. But ascorbic acid (AA) is able to reduce CoOOH to cobalt ion (Co2+), which causes decomposition and collapse of the CoOOH nanoflakes, and thereby the CoOOH nanoflakes would be deprived of the oxidase-like property. Based on the principle, fluorescent and colorimetric dual-mode detection of AA was achieved. Alkaline phosphatase (ALP) can make L-ascorbic acid-2-phosphate (AAP) hydrolyze to yield AA. As a result, with the assist of AAP, the selective and sensitive dual-mode assay of ALP activity has been realized successfully by using fluorescence and UV-vis absorption spectroscopy. Quantitative analysis of ALP in human serum samples and ALP inhibitor investigation were performed by this sensing system. Given the economical and sensitive properties, the proposed method based on the CoOOH nanoflakes has great potential for not only probing ALP activity in biological system but also screening potential ALP inhibitors. Meanwhile, in this study, a new insight has been provided for the application of CoOOH nanoflakes to develop sensitive and convenient sensors.