Cellular senescence, a process that halts cell cycle, is a cellular stress response to various stimuli. However, there is lack of sufficient understanding of senescence in living organisms, largely due to the shortage of detection tools for senescent cells in tissues and organs. Herein, we developed a self-immobilizing NIR Probe NIR-BG2 using quinone methide chemistry for imaging cellular senescence in vivo. The probe possesses a NIR fluorophore and an anchoring group enabling deep tissue imaging and signal retention. In this work, our designed probe exhibited a dramatic NIR fluorescent response upon activation of β-galactosidase. In order to confirm the attachment of NIR fluorescent tag with β-galactosidase via a covalent bond, fluorescent western blot experiment was carried out. The NIR signal from our probe could be clearly visualized on the band of β-galactosidase. By contrast, no NIR signal was overserved in the control probe NIR-BG1 lacking the anchoring group. These results validated that quinone methide chemistry functionalized the anchoring ability. Next, we examined the fluorescent imaging in both CT26.CL25 cells with a LacZ gene, and camptothecin (CPT)-treated HeLa cells, in which a biomarker for senescent cells, senescence–associated β–galactosidase (SA-β-Gal) was induced after treatment with CPT. As expected, in these two groups NIR-BG2 manifested a higher fluorescence intensity compared to its control probe NIR-BG1. The fluorescence discrepancy can also be further distinguished by flow cytometry. After evaluating the capability of this probe for imaging drug-induced senescence in vitro, we examined its capability of detecting cellular senescence in mice bearing human tumor xenografts treated with CPT. After 6 h post tail injection of NIR-BG1 and NIR-BG2, the fluorescent NIR signal could be detected in both groups, while a higher signal was observed with NIR-BG2 due to the presence of anchoring group. Taken together, the data indicated that our probe was an efficient tool for in vivo imaging of cellular senescence with long-time signal retention.

Self-immobilizing NIR probe for imaging of cellular senescence in vivo

2019 Spring National Meeting

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