Fluorescence of europium activated by molecular-like silver clusters for the detection of alkaline phosphatase activity

Alkaline phosphatase (ALP) is abnormally expressed in some cancers and promotes the growth, metastasis, and invasion of cancer cells. The detection of ALP is of great significance for both pathological study and clinical detection. In this work, a europium (Eu)-based fluorescence detection sensor was prepared in a mild reaction condition. LaF 3 :Eu nanoparticles was mixed with ethylene imine polymer (PEI) and Ag + ions. PEI was used as stabilizer and reducing agent, and Ag + ions were reduced as molecular-like silver clusters (ML-Ag NCs). The fluorescence of LaF 3 :Eu nanoparticles was enhanced by ML-Ag NCs through energy transfer. When ascorbic acid 2-phosphate (AAP) was hydrolyzed to ascorbic acid (AA) in the presence of ALP, AA reduced Ag + ions to silver nanoparticles (Ag NPs) and quenched the fluorescence of LaF 3 :Eu/PEI/Ag. The activity of ALP was detected by measuring the fluorescence intensity of Eu 3+ at 618 nm. In the concentration range from 2.0 to 16.0 U/L, the fluorescence intensity ratio ((F 0 –F)/F 0 ) had a linear relationship with the logarithm of ALP concentration. The limit of detection (LOD) was 1.3 U/L. Moreover, the ALP activity was detected successfully in cancer cells by this method. The sensing platform has application potential in the detection of ALP activity in biological systems.