A novel near-infrared viscosity probe based on synergistic effect of AIE property and molecular rotors for mitophagy imaging during liver injury

Mitophagy, a specialized form of autophagy, holds the key to cellular metabolism and physiology. Viscosity is a significant marker for visualization of the mitophagy process in real-time. Hence, development of well-performing viscosity probe is beneficial to study mitophagy-related dynamic physiological and pathological processes. Here, a new strategy was proposed by combination of AIE property and molecular rotors to design novel viscosity probe. The probe named TPA-Py was obtained by Knoevenagel condensation reaction of AIE unit and pyridine salt, which giving the probe excellent near-infrared emission, good water-solubility and mitochondrial targeting ability. Most importantly, TPA-Py owns two rotatable parts of triphenylamine and double bond, enabling the probe to equip with AIE property and sensitive recognition units for viscosity. With the environmental viscosity increasing, the rotation of the molecular rotor and the AIE unit is restricted effectively, the probe displayed strong fluorescence. Then, TPA-Py was successfully employed for monitoring the mitophagy process in A549 cells by imaging viscosity alterations. As mitophagy constitutes an important consideration in the pathogenesis of drug-induced liver injury, TPA-Py was also applied to explore the variation of viscosity in production and remediation pathways of APAP-induced liver injury. These results demonstrated that TPA-Py was a highly sensitive viscosity probe which holds great potential of biological applications.