Cathepsin B Responsive Peptide–Purpurin Conjugates Assembly-Initiated in Situ Self-Aggregation for Cancer Sonotheranostics

Sonodynamic therapy (SDT) was hampered by the sonosensitizers with low bioavailability, tumor accumulation, and therapeutic efficiency. In situ responsive sonosensitizer self-assembly strategy may provide a promising route for cancer sonotheranositics. Herein, an intelligent sonotheranostic peptide–purpurin conjugate (P18-P) is developed that can self-assemble into supramolecular structures via self-aggregation triggered by rich enzyme cathepsin B (CTSB). After intravenous injection, the versatile probe could achieve deep tissue penetration because of the penetration sequence of P18-P. More importantly, CTSB-triggered self-assembly strongly prolonged retention time, amplified photoacoustic imaging signal for sensitive CTSB detection, and boosted reactive oxygen species for advanced SDT, evoking specific CTSB responsive sonotheranostics. This peptide–purpurin conjugate may serve as an efficient sonotheranostic platform for the early diagnosis of CTSB activity and effective cancer therapy.