Fluorescence “turn on-off” detection of heparin and heparinase I based on the near-infrared emission polyethyleneimine capped Ag2S quantum dots

A novel fluorescence “turn on-off” method for sensitive and selective detection of heparin and heparinase I was developed based on near infrared Polyethyleneimine Capped Ag 2 S Quantum Dots (PEI-Ag 2 S QDs). The fluorescence “turn-on” arose from aggregation-induced emission enhancement (AIEE) characteristics of PEI-Ag 2 SQDs induced by electrostatic interaction between PEI-Ag 2 SQDs and heparin. Heparinase I, which can specifically hydrolyze heparin into short fragments would de-aggregate PEI-Ag 2 S QDs/heparin system and lead to fluorescence “turn-off”. Under optimal conditions described, the fluorescence enhancement at 685   nm was linearly related to the concentration of heparin and heparinase I in the range of 0.069–2.275   μM and 0–103   ng   mL −1 with the relative correlation coefficient of R 2   =   0.997 and 0.99 and detection limit as low as 6   nM and 0.5   ng   mL −1 , respectively. The activity of the heparinase I was further investigated using steady-state kinetic for the reaction. In ddition, the proposed method was successfully utilized in serum samples, which presaged more opportunities for application in related biochemical and biomedical researches.