Rotor-Tuning Boron Dipyrromethenes for Dual-Functional Imaging of Aβ Oligomers and Viscosity

Abstract

Alzheimer's disease (AD), known as a common incurable and elderly neurodegenerative disease, has been widely explored for accurate detection of its biomarker (Aβ oligomers) for early diagnosis. Although great efforts have been made, it is still of great importance to develop fluorescence probes for Aβ oligomers with good selectivity and low background. Herein, starting from BODIPY493/503 (a commercial dye for neutral lipid droplets), which exhibited a small Stokes shift and no response toward Aβ peptides, two fluorescence probes <b>5MB-SZ</b> and <b>B-SZ</b> with a benzothiazole rotor at the 2-position of the BODIPY core and a methyl or benzyl group at the meso position have been designed and synthesized, which exhibited excellent optical properties/stability and could successfully image β-amyloid fibrils and viscosity. Upon exposure to Aβ oligomers, the fluorescence intensity of <b>5MB-SZ</b> was enhanced by 43.64-fold with the corresponding fluorescence quantum yields changing from 0.85% to 27.43%. Meanwhile, probe <b>5MB-SZ</b> showed a highly sensitive viscosity response in both solutions and living cells. In vitro and in vivo experiments confirmed that probe <b>5MB-SZ</b> exhibited an excellent capacity for imaging β-amyloid fibrils. Therefore, <b>5MB-SZ</b>, as a rotor-tuning BODIPY analogue, could possibly serve as a highly potential and powerful fluorescence probe for early diagnosis of AD.