CTSB and breast cancer: Taking advantage of precise photoacoustic imaging, an intelligent photoacoustic probe Cypate-CBT, which could effectively assemble into cypate-containing nanoprobes in response to overgenerated GSH and cathepsin B in tumor cells, was prepared by Liang’s group [251] for the accurate and specific monitoring of cathepsin B. In comparison to unmodified Cypate, this nanoprobe showed a higher photoacoustic signal in cathepsin B-positive breast cancer models, supporting the intracellular accumulation of the nanoprobes after cathepsin B-triggered self-assembly.