Investigating the oxidase-like activity of a Co–Fe Prussian blue analogue nanocube prepared in situ and its applications in the colorimetric detection of ascorbic acid, alkaline phosphatase, α-glucosidase, and ascorbic acid oxidase

Abstract

Herein, a Co–Fe Prussian blue analogue nanocube (Co–Fe PBA NC) was prepared in situ via a simple and rapid coprecipitation method at room temperature, and the synthesized nanocube was systematically characterized. The Co–Fe PBA NC was proven to have intrinsic oxidase-like activity, which can catalyze the production of reactive oxygen species, such as superoxide anions (O₂˙⁻), hydroxyl radicals (˙OH), and singlet oxygen (¹O₂), in a dissolved oxygen system without the presence of hydrogen peroxide (H₂O₂). By making full use of the oxidase-like activity of the Co–Fe PBA NC and using the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB), a colorimetric sensor was fabricated for the detection of ascorbic acid (AA) and its related biological enzymes’ activities, including alkaline phosphatase (ALP), α-glucosidase (α-Glu), and ascorbic acid oxidase (AAO), in human serum. This study presents an oxidase mimic that can be synthesized via a simple, rapid, and low-cost method, which overcomes the defects of cumbersome and time-consuming synthetic process, dependence on professional instruments and high cost of some previously reported nanozymes. In addition, this study provides a new multifunctional colorimetric sensing platform for AA and its related biological enzymes, showing great potential in biological assays.