Abstract
In this paper, we propose a simple colorimetric method for the sensitive and selective detection of alkaline phosphatase (ALP) activity based on the turn off/turn on oxidase mimic activity of His@AuNCs. His@AuNCs/graphene oxide hybrids (His@AuNCs/GO) were easily obtained using the self-assembly method with poly (diallyldimethylammonium chloride) (PDDA)-coated GO and showed high oxidase-like activity compared with His@AuNCs. We found that the pyrophosphate ion (P2O74−, PPi) could effectively inhibit the oxidase mimic activity of His@AuNCs/GO, and the hydrolysis of PPi by ALP restored the inhibited activity of His@AuNCs/GO, enabling them to efficiently catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate the blue oxidized product oxTMB. The intensity of the color showed a linear dependency with the ALP activity. ALP was detected in the linear range of 0–40 mU/mL with a low detection limit (LOD) of 0.26 mU/mL (S/N = 3). The proposed method is fast, easy, and can be applied to monitor the ALP activity in serum samples accurately and effectively, which suggests its practicability and reliability in the detection of ALP activity in clinical practice.
Highlights
Alkaline phosphatase (ALP) is widely present in the tissues and organs of biological organisms and can catalyze the hydrolysis and transphosphorylation of a variety of phosphate compounds, including DNA, proteins, and other small molecules [1,2]
ALP was used as the catalyst in the hydrolysis of ascorbic acid-2-phosphate (AA-P) to ascorbic acid (AA); the AA was used to reduce the silver ions to generate a silver shell on the Au nanoclusters (AuNCs), which led to a perceptible color change producing the signal readout [14]
As the proposed method was based on the modulation of the oxidase-like activity of His@AuNCs/graphene oxide (GO), we first investigated the inhibitory effects of pyrophosphate ion (PPi) on the activities of
Summary
Alkaline phosphatase (ALP) is widely present in the tissues and organs of biological organisms (e.g., bones, liver, intestine, kidneys, and placenta) and can catalyze the hydrolysis and transphosphorylation of a variety of phosphate compounds, including DNA, proteins, and other small molecules [1,2]. Using plasmonic gold nanorods, Gao et al designed a colorimetric assay to determine the ALP activity In this method, ALP was used as the catalyst in the hydrolysis of ascorbic acid-2-phosphate (AA-P) to ascorbic acid (AA); the AA was used to reduce the silver ions to generate a silver shell on the Au nanoclusters (AuNCs), which led to a perceptible color change producing the signal readout [14]. ALP was used as the catalyst in the hydrolysis of ascorbic acid-2-phosphate (AA-P) to ascorbic acid (AA); the AA was used to reduce the silver ions to generate a silver shell on the Au nanoclusters (AuNCs), which led to a perceptible color change producing the signal readout [14] These approaches can provide a simple and visual detection of ALP, plasmonic nanomaterials suffer from non-specificity of ions in complex biological samples [22], resulting in poor sensitivity and a limited linear range. Materials and Methods proposed method shows a good linear relationship in the range of 0–40 mU/mL with a
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