Cellular senescence imaging and senolysis monitoring in cancer therapy based on a β-galactosidase-activated aggregation-induced emission luminogen.

Cellular senescence is a permanent state of cell cycle arrest characterized by increased activity of senescence associated β-galactosidase (SA-β-gal). Notably, cancer cells have been also observed to exhibit the senescence response and are being considered for sequential treatment with pro-senescence therapy followed by senolytic therapy. However, there is currently no effective agent targeting β-galactosidase (β-Gal) for imaging cellular senescence and monitoring senolysis in cancer therapy. Aggregation-induced emission luminogen (AIEgen) demonstrates strong fluorescence, good photostability, and biocompatibility, making it a potential candidate for imaging cellular senescence and monitoring senolysis in cancer therapy when endowed with β-Gal-responsive capabilities. In this study, we introduced a β-Gal-activated AIEgen named QM-β-gal for cellular senescence imaging and senolysis monitoring in cancer therapy. QM-β-gal exhibited good amphiphilic properties and formed aggregates that emitted a fluorescence signal upon β-Gal activation. It showed high specificity towards the activity of β-Gal in lysosomes and successfully visualized DOX-induced senescent cancer cells with intense fluorescence both in vitro and in vivo. Encouragingly, QM-β-gal could image senescent cancer cells in vivo for over 14 days with excellent biocompatibility. Moreover, it allowed for the monitoring of senescent cancer cell clearance during senolytic therapy with ABT263. This investigation indicated the potential of the β-Gal-activated AIEgen, QM-β-gal, as an in vivo approach for imaging cellular senescence and monitoring senolysis in cancer therapy via highly specific and long-term fluorescence imaging. STATEMENT OF SIGNIFICANCE: This work reported a β-galactosidase-activated AIEgen called QM-β-gal, which effectively imaged DOX-induced senescent cancer cells both in vitro and in vivo. QM-β-gal specifically targeted the increased expression and activity of β-galactosidase in senescent cancer cells, localized within lysosomes. It was cleared rapidly before activation but maintained stability after activation in the DOX-induced senescent tumor. The AIEgen exhibited a remarkable long-term imaging capability for senescent cancer cells, lasting over 14 days and enabled monitoring of senescent cancer cell clearance through ABT263-induced apoptosis. This approach held promise for researchers seeking to achieve prolonged imaging of senescent cells in vivo.