Monitoring the activity and inhibition of alkaline phosphatase via quenching and restoration of the fluorescence of carbon dots

Abstract

We report that the fluorescence of carbon dots (C-dots) in water is quenched by the addition of Cu 2+ ions, and that the subsequent addition of pyrophosphate (PPi) restores fluorescence. This is likely to be due to the coordination of Cu 2+ by PPi. This effect forms the basis for a method to determine the activity and inhibition of the enzyme alkaline phosphatase (ALP). If ALP is added to a system composed of C-dots, Cu 2+ and PPi, fluorescence will decrease over time because ALP catalyzes the hydrolysis of PPi to form orthophosphate (Pi). This results in a release of the quencher Cu 2+ . The decrease in fluorescence is related to the activity of ALP. The method is simple and displays good sensitivity (with a limit of detection of 1 units per L) and selectivity. The method was successfully applied to the determination of ALP in serum samples. We also have studied the inhibitory effect of Pi on the activity of ALP. We presume that this method holds a large potential in terms of diagnosis of ALP-related diseases, to evaluate the function of ALP in biological systems and in screening for potential inhibitors of ALP.

Carbon dots: synthetic methods and applications as fluorescent probes for the detection of metal ions, inorganic anions and organic molecules

“…These CDs got a detection limit of 115 nM over a broad concentration range of Cu 2+ from 0.333 to 66.6 μM. Kang's group synthesized CDs by nitric acid oxidation of glucose for Cu 2+ detection [60]. Similarly, the fluorescence of CDs was quenched with Cu 2+ because of the cupric amine complexes between Cu 2+ and amine groups of CDs.…”

Gold Nanocluster-catalyzed Luminol Chemiluminescent Sensing Method for Sensitive and Selective Detection of Alkaline Phosphatase

“…7 Therefore, the development of simple and sensitive methods for the detection of ALP activity is of great importance. Over the past few years, a variety of methods including colorimetry, 8,9 fluorescence, [10][11][12] surface-enhanced Raman scattering, 13 electrochemistry, 14,15 photoelectrochemistry, 16 and electrochemiluminescence, 17 have been established for the detection of ALP activity. Although the reported colorimetric methods for ALP detection are simple, the detection sensitivity is poor.…”

Pyrophosphate as substrate for alkaline phosphatase activity: A convenient flow‐injection chemiluminescence assay

“…Recent colorimetric methods usually take advantage of the aggregation or disaggregation induced changes in the solution color of gold or silver nanoparticles. Quantum dots, conjugated polyelectrolytes, small molecular probes, nanoclusters and carbon dots have been employed successfully for monitoring ALP activity using their specific fluorescence. Electrochemistry‐based methods using electro‐active materials have been adopted to detect ALP activity .…”