A NIR fluorescent probe for viscosity detection and its application to spinal cord imaging in mice with multiple sclerosis.

Cellular microenvironment viscosity, as a key biophysical parameter, is significantly associated with disease processes such as tumors, atherosclerosis, and multiple sclerosis (MS). The core pathological mechanism of MS involves neuroinflammation-mediated demyelination and axonal degeneration, which ultimately leads to multi-system neurological dysfunction. In this study, we developed a novel near-infrared fluorescent probe, CABT (based on a dimethylaminobenzene-benzothiazole dye), which achieves viscosity-responsive fluorescence enhancement through an intramolecular single-bond rotationally restricted mechanism. With high selectivity, deep tissue penetration and low background interference properties, the probe was successfully applied to HT22 cell imaging and visualization of LPS-activated BV2 microglia. The probe also enables the detection of inflammatory infiltration in experimental autoimmune encephalomyelitis (EAE) models, providing a novel molecular tool for early diagnosis and treatment of MS.