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-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-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 mu M and 0-103 ngmL(-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 ngmL(-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. (C) 2016 Elsevier B.V. All rights reserved.