A far-red/near-infrared fluorescence probe with large Stokes shift for monitoring butyrylcholinesterase (BChE) in living cells and in vivo.

Accurate detection of butyrylcholinesterase (BChE) activity is imperative to understand its biological function and diagnose related disease. Far-red (FR)/Near-Infrared (NIR) fluorescent probe with large Stokes shift for BChE detection is extremely important. In this study, we reported a new "off-on" FR/NIR fluorescent probe (DX-2) with large Stokes shift (110 nm). DX-2 was constructed through cyclopropionate to pull-push the optical tuable hydroxyl group of chloro-substituted dicyanoisophorone fluorophore. DX-2 (λex/λem = 555/665 nm) featured high sensitivity (LOD∼0.08 U/mL) and selectivity, good pH practicability, low toxicity and good cell membrane permeability with a bright emission triggered by BChE. Furthermore, DX-2 exhibited good optical performance to image BChE activity in living cells. More importantly, the FR/NIR probe DX-2 was successfully applied to real-time monitor BChE in live tumor-bearing mouse model. These studies suggest that probe DX-2 has potential applicable value for detecting BChE in living biological systems and diagnosing BChE-related diseases.