Visualization of endoplasmic reticulum viscosity in the liver of mice with nonalcoholic fatty liver disease by a near-infrared fluorescence probe

Nonalcoholic fatty liver disease (NAFLD) can cause serious liver damage. Early diagnosis and effective treatment of NAFLD can greatly improve treatment rates. The initiation and development of NAFLD has been closely linked to endoplasmic reticulum (ER) stress, which might cause ER viscosity variations. Therefore, if the internal relationship between ER viscosity and NAFLD is clarified, an effective approach for early diagnosis may result. Herein, we fabricated a novel near-infrared (NIR) fluorescence imaging probe, Er-V, for monitoring ER viscosity through a molecular rotor strategy. Er-V exhibited a strong NIR fluorescence signal (at 626 nm) when the environmental viscosity hindered the rotation of the malononitrile group. Using Er-V, we successfully observed a significant enhancement in viscosity in the liver of mice with NAFLD. Therefore, this imaging method based on Er-V is expected to provide a new approach for early detection and diagnosis of NAFLD.