Near-Infrared Fluorescent Probe with New Recognition Moiety for Specific Detection of Tyrosinase Activity: Design, Synthesis, and Application in Living Cells and Zebrafish.

Fluorescence imaging of tyrosinase (a cancer biomarker) in living organisms is of great importance for biological studies. However, selective detection of tyrosinase remains a great challenge because current fluorescent probes that contain the 4-hydroxyphenyl moiety show similar fluorescence responses to both tyrosinase and some reactive oxygen species (ROS), thereby suffering from ROS interference. Herein, a new tyrosinase-recognition 3-hydroxybenzyloxy moiety, which exhibits distinct fluorescence responses for tyrosinase and ROS, is proposed. Using the recognition moiety, we develop a near-infrared fluorescence probe for tyrosinase activity, which effectively eliminates the interference from ROS. The high specificity of the probe was demonstrated by imaging and detecting endogenous tyrosinase activity in live cells and zebrafish and further validated by an enzyme-linked immunosorbent assay. The probe is expected to be useful for the accurate detection of tyrosinase in complex biosystems.