A dual-functional fluorescence probe for detection of Aβ aggregates and hydroxyl radicals

Synchronous detection of Aβ aggregates and reactive oxygen species (ROS) would provide direct insight to reveal the complicated correlations between the two crucial Alzheimer's disease (AD) hallmarks. Herein, the first fluorescence probe (Quin-HCy) for dual-functional detection of Aβ aggregates and the highly destructive ROS hydroxyl radicals (•OH) is developed. Quin-HCy is designed with a blood-brain barrier (BBB) permeable quinoline fluorophore and a •OH-responsive hydrocyanine moiety. Quin-HCy shows obvious fluorescence increases in response to Aβ aggregates and •OH at 450 nm and 770 nm, respectively. The large spectral shift (∼ 320 nm) is advantageous for the independent detection of these two analytes in two distant channels. Quin-HCy has been used to image •OH in cells through the addition of Fenton reagents, stimulation with PMA and induction of ferroptosis. Most importantly, fluorescence imaging with Quin-HCy shows that significant •OH is generated in Aβ aggregate-treated neuron cells, which provides direct evidence for the high dependence between Aβ aggregates and •OH in the etiology of AD. Besides, Quin-HCy has favorable BBB permeability, and is able to image Aβ plaques and •OH in AD mice brain slices.