Visualizing Senescent–Normal Cell Boundaries Through Environment-Dependent Bidirectional Luminescent Contrast

Unlike tumors, senescent tissues lack well-defined boundaries at the cellular level because senescence develops gradually, leading to spatial intermixing of the senescent and normal cells. This ambiguity poses a major conceptual challenge for surgical decision-making, where insufficient resection risks recurrence while excessive removal compromises tissue integrity. Existing probes fail to resolve this ambiguity because signal-silent regions may represent either normal cells or unlabeled senescent populations. Therefore, designing new signal logic for luminescent probes (e.g., environment-dependent bidirectional signal modulation, depending on the cellular environment of the normal and senescent cells, respectively), is crucial for precise delineation of senescent–normal cell boundaries. In this work, luminescent probes enabling bidirectional photomodulation were constructed by modifying hydrophilic β-galactose groups onto hydrophobic hydroxyl-hexathiobenzene, which can exhibit the following performance: (1) Direction 1: In normal cells, the probes remain non-emissive, but become emissive upon photoexcitation-induced aggregation (signal up-regulated); (2) Direction 2: In senescent cells, β-galactosidase (β-Gal)-triggered deglycosylation immediately generates hydrophobic products with an aggregation-induced emission characteristic, whose strong emission can be down-regulated upon a following photoexcitation-induced molecular reorganization. This environment-dependent bidirectional photomodulation using the same probe enables dynamic contrast between senescent and normal cells, thereby providing a new paradigm of resolving biological ambiguity at the cellular scale.