Advances in Fluorescent Probes Targeting Senescence‐Associated β‐Galactosidase for Senescence Imaging

Aging is a systemic biological process that spans multiple levels, including molecules, cells, tissues, and organs. Cellular senescence is regarded as one of the key mechanisms driving functional decline, chronic inflammation, and the onset and progression of age‐related diseases. Among the numerous biomarkers of senescence, senescence‐associated β‐galactosidase (SA‐β‐gal) has become one of the most widely used classical indicators in cellular senescence research. However, conventional X‐gal staining and lysate‐based assays largely rely on endpoint, ex vivo, or semi‐quantitative readouts, making it difficult to meet the growing demand for real‐time, in situ, dynamic, and highly sensitive visualization of senescent states in live cells, tissue sections, and living organisms. The development of fluorescence imaging technologies, particularly near‐infrared fluorescence imaging, has provided a new toolkit for detecting SA‐β‐gal activity. Fluorescent probes containing a β‐D‐galactose unit can be activated by β‐galactosidase, resulting in the recovery or change of fluorescence signals. This review systematically summarizes recent advances in senescence imaging targeting SA‐β‐gal, including turn‐on probes, ratiometric probes, AIE‐based probes, and nanoprobes. In particular, we highlight strategies to improve the specificity of SA‐β‐gal imaging, enhance the ability to distinguish SA‐β‐gal activity in senescent cells from that in non‐senescent tumor cells, and further discuss the challenges and opportunities in this field.