Ruthenium-Based Sonoafterglow Probes for Tumor-Specific Theranostics

Afterglow imaging uses delayed luminescence to suppress tissue autofluorescence and improve signal-to-background ratios for in vivo diagnostics and therapy. However, because afterglow induction typically requires external light, conventional photoactivated approaches remain suboptimal. Here, we report two hybrid molecular sonoafterglow luminophores that pair tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)₃) as a sonosensitizer with a phenoxy-adamantylidene afterglow substrate: cRuPA and ncRuPA, which are connected via a conjugated alkyne and a nonconjugated amide linker, respectively. After ultrasound treatment, only ncRuPA produces a strong sonoafterglow. In cRuPA, rapid electron transfer across the conjugated alkyne cleaves the dioxetane intermediate before emission can occur, whereas the nonconjugated amide in ncRuPA blocks this transfer, stabilizing the dioxetane and enabling sustained luminescence. ncRuPA is further developed into an activatable probe (ncRuPA_APN) that selectively turns on its sonoafterglow in response to the cancer biomarker aminopeptidase N. ncRuPA_APN enables sensitive tumor imaging and mediates efficient sonodynamic therapy via ultrasound-triggered singlet oxygen production. These Ru-based sonoafterglow probes represent the first hybrid sonoafterglow molecules and open new molecular-design routes toward cancer theranostics.