Reactive oxygen species (ROS), such as H2O2, are upregulated in many diseases including diabetes,38 cardiovascular diseases,39 neurodegenerative disorders,40 and cancer.41,42 The Tsien group designed a ROS-sensitive ACPP by introducing a 4-boronic mandelic acid moiety between a cationic CPP and anionic inhibitory domain (Table 2, entry 8).43 The ACPP was further equipped with fluorescein (FITC) on the CPP and a cyanine5 red dye (Cy5) on the inhibitory domain. Here, ACP3 is linked to cardiovascular disorder.