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 Ag2S Quantum Dots (PEI-Ag2S QDs). The fluorescence “turn-on” arose from aggregation-induced emission enhancement (AIEE) characteristics of PEI-Ag2SQDs induced by electrostatic interaction between PEI-Ag2SQDs and heparin. Heparinase I, which can specifically hydrolyze heparin into short fragments would de-aggregate PEI-Ag2S 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 R2 = 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.