Green-emitting carbon dots-protein fluorescence sensing system for specific and sensitive detection of trypsin in urine

Trypsin is a kind of digestive enzyme capable of catalyzing the hydrolysis of proteins. Abnormal changes in the levels of trypsin can cause a series of pancreatic-related diseases. Therefore, based on the special interface interaction between green-emitting ionic liquid-based carbon dots (G-CDs) and BSA, a highly sensitive fluorescence "on-off" mechanism was developed for detecting trypsin in urine. The G-CDs were synthesized by a onestep hydrothermal approach using 2,5-dihydroxybenzoic acid (2,5-DHBA) and 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIM]PF4). The interaction between G-CDs and bovine serum albumin (BSA) led to the formation of the G-CDs-BSA fluorescence sensing system, which induced aggregation and fluorescence enhancement of G-CDs. The G-CDs-BSA system was disrupted under optimal incubation conditions after the addition of trypsin, and the fluorescence was quenched. According to the fluorescence quenching value (Delta F) of the system, the quantitative analysis of trypsin in urine was realized and demonstrated good recoveries. This study not only developed a novel fluorescence sensing system with excellent performance for trypsin detection, but also provided a theoretical basis for the binding of carbon dot-protein systems.