Ultrasensitive Determination of Trypsin in Human Urine Based on Amplified Fluorescence Response

The determination of trypsin activity in human urine is important for evaluating pancreatic disease. We designed an effective fluorescence sensing strategy based on a self-assembled amphiphilic pyrene/protamine complex system that provides an amplified fluorescence response for highly sensitive and selective detection of trypsin. In aqueous solution, the functionalized pyrene formed fluorescent, π-extended aggregates inside micelles, which were effectively quenched by protamine (a trypsin substrate). However, this quenched fluorescence was very sensitively recovered by the trypsin's enzymatic reaction, and this was attributed to a marked reduction in enhanced exciton migration caused by protamine in π-delocalized pyrene aggregates. The devised sensing platform was successfully utilized to selectively and sensitively detect trypsin at very low concentrations (0.03-0.5 μg mL^-1) in non-pretreated human urine and to screen for trypsin inhibitors at concentrations of 0.1-5.0 μg mL^-1.