A Pyrene-Derived Fluorescent Probe for the Visual Detection of Protamine and Trypsin Activity

A pyrene-derived fluorescent probe (P4CG) was designed and synthesized for the purpose of detecting protamine and trypsin activity. The anionic probe self-assembled with protamine, driven by electrostatic and hydrophobic interactions, exhibiting a sensing behavior towards protamine in a fluorescence ratiometric manner. The assay demonstrated high sensitivity, with a limit of detection (LOD) of 13.8 ng/mL, and exhibited selectivity in the HEPES buffer solution. Moreover, the P4CG-protamine complex enables the monitoring of trypsin activity with satisfactory sensitivity and selectivity. The presence of the trypsin inhibitor resulted in the inhibition of the hydrolysis of protamine, which in turn led to a diminished fluorescence recovery. Consequently, this assay can be employed for the screening of trypsin inhibitors.