A novel sensor for the detection of alkaline phosphatase activity based on the self-assembly of Eu3+-doped oxide nanoparticles and heptamethine cyanine dye

A non-fluorescent self-assemblage of Y0.6Eu0.4VO4 nanoparticle (NP) and heptamethine cyanine dye bearing phosphate group p-Cy7-A, NP-p-Cy7-A, was the first constructed and used as an alkaline phosphatase (ALP) sensor. Herein, Y0.6Eu0.4VO4 NP and new synthesized p-Cy7-A were employed respectively as donor and acceptor of Fluorescence Resonance Energy Transfer. With the help of phosphate group, p-Cy7-A as a dark quencher was captured on Y0.6Eu0.4VO4 NP surface to form non-fluorescent NP-p-Cy7-A in situ. The disintegration of NP-p-Cy7-A was triggered by the removal of phosphate group in p-Cy7-A catalyzed by ALP, and released fluorescent Y0.6Eu0.4VO4 NP. Thus NP-p-Cy7-A assemblage as a selective and sensitive sensor can very well responded to the amount and activity of ALP by measuring the fluorescent intensity at 620 nm (excited at 270 nm). This sensor can not only accurately measure the concentration of ALP (0.03-1.65 U/mL), but also be applied to detect the activity of ALP and screen its inhibitor by a simple mix-and-measure manner.