A rapid-response near-infrared fluorescent probe with a large Stokes shift for senescence-associated β-galactosidase activity detection and imaging of senescent cells

Detection of senescence-associated β-galactosidase (SA-β-gal) activity at an increased lysosomal pH is one of the most reliable approaches for probing senescent cells. Herein, we developed a novel near-infrared fluorescent probe (KSL0401) for sensing SA-β-gal activity and applying in visualization of aging. This probe was designed by connecting a cleavable d-galactose residue to the coumarin-dicyanoisophorone hybrid fluorophore KSL0401-OH via a β-glycosidic bond. The spectral properties of KSL0401 reaction with β-gal were measured in aqueous solution at pH 6.0, and a remarkable enhancement of fluorescence emission at 706 nm was observed, along with a visible colorimetric change. Probe KSL0401 was highly selective and sensitive to SA-β-gal, and displayed large Stokes shift (218 nm) and good biocompatibility. Moreover, it exhibited extremely rapid response to β-gal within 80 s, which surpassed most of the reported SA-β-gal probes. Additionally, KSL0401 also enabled to detect the endogenous SA-β-gal activity in living cells, and distinguish between senescent cells and non-senescent cells and qualify the degree of aging. These findings demonstrate that KSL0401 is a potential detection tool in the imaging research of aging.