Near-infrared fluorescent probe based on aggregation-induced emission for in vivo viscosity imaging

The functions of mitochondria, the powerhouses of the cell, depend intimately on the intracellular and extracellular physicochemical environment. Viscosity plays a critical regulatory role in mitochondrial activities across multiple physiological processes. Abnormal viscosity not only disrupts mitochondrial function, leading to dysregulation of cellular energy metabolism homeostasis, but is also closely associated with various pathological mechanisms. Herein, we innovatively designed and synthesized a near-infrared fluorescent probe, WG-1, based on a triphenylamine scaffold. Fluorescence spectral characterization revealed that WG-1 exhibits exceptional viscosity-responsive properties, a strong logarithmic linear correlation (R₁² = 0.99, R₂² = 0.996), and prominent aggregation-induced emission characteristics. Notably, the probe exhibited outstanding selectivity and anti-interference capability, with fluorescence signals remaining unaffected by changes in pH and polarity as well as the presence of diverse ions. Cellular experiments demonstrated that in addition to possessing excellent biocompatibility, WG-1 achieved precise mitochondrial localization and dynamic tracking of fluctuations in viscosity. In vivo experiments further verified that WG-1 enables the real-time monitoring of mitochondrial viscosity in zebrafish and detects notable viscosity-responsive signals in a murine liver disease model. Collectively, WG-1 provides a robust tool for in-depth exploration of disease mechanisms linked to mitochondrial viscosity dysregulation.