Fluorescence assay for alkaline phosphatase activity based on energy transfer from terbium to europium in lanthanide coordination polymer nanoparticles

Abstract

In this study, bimetallic lanthanide coordination polymer nanoparticles (Tb-GMP-Eu CPNs) were developed for sensing alkaline phosphatase (ALP) by utilizing guanine monophosphate (GMP) as the bridge ligand to self-assemble with Tb³⁺ and Eu³⁺ in Tris–HCl buffer solution. In this polymer framework, an efficient energy transfer from Tb³⁺ to Eu³⁺ occurred because the emission energy of Tb³⁺ matched well with the absorption energy of Eu³⁺. As a result, the synthesized Tb-GMP-Eu CPNs exhibited the characteristic red emission of Eu³⁺ when excited at 290 nm. When ALP was introduced into the Tb-GMP-Eu CPNs system, it would destruct the combination between Tb and GMP by a dephosphorylation process, resulting in interruption of energy transfer from Tb³⁺ to Eu³⁺ and therefore the fluorescence quenching of Eu³⁺. Based on these facts, a fluorescence assay based on bimetallic lanthanide coordination polymer nanoparticles for ALP detection was developed. Such a Tb-GMP-Eu CPNs sensor exhibited sensitive response to ALP with a detection limit down to 0.004 U L⁻¹. Moreover, the successful application of ALP inhibitor evaluation and determination of ALP in serum samples have been demonstrated. Therefore, the proposed method has great potential application for ALP detection in biological and clinical diagnosis.