Carbon dots sensitized lanthanide infinite coordination polymer nanoparticles: Towards ratiometric fluorescent sensing of cerebrospinal Aβ monomer as a biomarker for Alzheimer's disease

Herein, a novel ratiometric fluorescent probe based on CDs@Eu/GMP ICP nanoparticles was developed for the detection of A beta monomer in rat as a biomarker for Alzheimer's disease (AD) by fully exploring the competitive coordination interaction and by taking advantage of excellent optical property of carbon dots sensitized lanthanide infinite coordination polymer (ICP) nanoparticles. The carbon dots (CDs) with abundant functional groups were encapsulated into Eu/GMP ICPs through self-adaptive chemistry, which could not only sensitize the red fluorescence of Eu/GMP ICPs effectively, but also act as an internal reference for self-correction. In the absence of Cu2+, the as-formed CDs@Eu/GMP ICPs exhibited the characteristic emission of CDs at 400 nm and strong emission of Eu3+ at 592 nm, 615 nm, 650 nm and 694 nm. With the addition of Cu2+, the red fluorescence of Eu3+ decreased due to the coordination interaction between CDs and Cu2+, thus destroyed the antenna effect. After the subsequent addition of Ab monomer, the specific binding occurred between Cu2+ and A beta monomer, and then the red fluorescence of Eu3+ restored again. During this process, the fluorescence of CDs remained unchanged, thus could be used as an internal reference to cancel out the environmental fluctuation and was more adaptive for the detection of A beta monomer in biological fluids. The method demonstrated here was highly sensitive, free from the interference of other species in rat brain, the in vivo analysis of A beta monomer in CSF and different brain regions from normal rats and Alzheimer's rats could be realized, which was of great significance for better understanding the mechanism of AD and paving the way to understand the chemical essence involved in AD. (C) 2020 Elsevier B.V. All rights reserved.