Efficient ratiometric fluorescence probe based on dual-emission luminescent lanthanide coordination polymer for amyloid β-peptide detection

Abstract

As an important biomarker for early Alzheimer’s disease (AD) diagnostics and a valuable therapeutic target, amyloid β peptide (Aβ) in blood has attracted extensive attention concerning its detection and monitoring. The tough challenges for monitoring subtle changes of Aβ in blood are low expression and high interference from environmental factors. Here, we constructed a ratiometric sensor based on dual-emission luminescent lanthanide metal–organic coordination polymer (DE-LMOCP) as fluorescence probe for simple, sensitive and accurate detection of Aβ. The DE-LMOCP (luminol-Tb-GMP-Cu) fluorescent probe was composed of terbium ion(Tb3+) as the center metal ions, cupric ion(Cu2+) as a cofactor for Tb3+ fluorescence silence, guanine monophosphate (GMP) as a bridging ligand can strengthen the fluorescence of Tb3+, and luminol as an auxiliary ligand. In the DE-LMOCP fluorescent probe, the fluorescence of the GMP-Tb is quite weak because the existing cofactor Cu2+ prevents the energy transfer of intramolecular between GMP and Tb3+ and results in the quench of GMP-Tb fluorescence. The fluorescence of luminol acts as inner reference. In the presence of Aβ, the high binding affinity of Aβ for Cu2+ causes a remarkable emission enhancement of GMP-Tb and suppresses the quenching effect. However, the fluorescence emission of luminol remains constant as inner reference. Hence, sensitive and accurate determination of Aβ were performed by the ratio of the fluorescence of luminol (F430) to the Tb3+(F547). With this ratiometric probe, Aβ was determined with sensitivity down to 20 pM. Moreover, the ratiometric probe was successfully used to the detection of Aβ in human plasma with satisfactory results due to its capability to eliminate auto-fluorescence. Significantly, it exhibited sound specificity and selectivity to recognize Aβ1−40, and successfully applied to visual detection of Aβ, which validates the potential on-site application. Given the analytical characteristics with high sensitivity, specificity, and accuracy, the ratiometric fluorescence sensor may have great potential in applications of Aβ1−40 detection and the early diagnosis of Alzheimer’s disease, as well as point-of-care tests.